Newsletter Vol 21 Issue 3, 2013 – California Invasive Plant Council

Vol. 21, No. 3

Fall 2013

Cal-IPC News
Protecting California’s Natural Areas from Wildland Weeds
Newsletter of the California Invasive Plant Council. www.cal-ipc.org

Weeds
and

wildlife
Pipevine swallowtail butterfly and native bee
feeding on bull thistle (Cirsium vulgare) in
Walnut Creek Open Space. Photo by Brian
Murphy.

INSIDE
Controlling mayweed helps terns p. 4
Successful Spanish broom control p. 8
Staying “on label” in tidal waters p. 9
PlantRight rolls out nursery program p.10
Tracking eradication progress p. 11
Grazing as a management tool p.12

From the Director’s Desk

A ‘cottage industry of criticisms’
Cal-IPC
1442-A Walnut Street, #462
Berkeley, CA 94709
ph (510) 843-3902 fax (510) 217-3500
www.cal-ipc.org info@cal-ipc.org
A California 501(c)3 nonprofit organization

Protecting California’s lands and waters
from ecologically-damaging invasive plants
through science, education, and policy.
STAFF
Doug Johnson, Executive Director
Elizabeth Brusati, Science Program Manager
Agustín Luna, Business Manager
Bertha McKinley, Program Assistant
Dana Morawitz, Mapping Program Manager

DIRECTORS
John Knapp, President
The Nature Conservancy
Jason Casanova, Vice-President
Council for Watershed Health
Shawn Kelly, Treasurer
Southern California Wetlands Recovery Project
Peter Schuyler, Secretary
Ecological Consultant
Peter Beesley
Pacific Gas & Electric Company
Jutta Burger
Irvine Ranch Conservancy
Jennifer Funk
Chapman University
Gery Gero
Climate Action Reserve
Doug Gibson
San Elijo Lagoon Conservancy
Jason Giessow
Dendra, Inc.
Kim Hayes
Elkhorn Slough Foundation
Annabelle Kleist
Capitol Impact
Dan Knapp
Los Angeles Conservation Corps
Virginia Matzek
Santa Clara University
Chris McDonald
UC Cooperative Extension
Colleen Murphy-Vierra
California Dept. of Food & Agriculture
STUDENT LIAISONS
Bridget Hilbig
UC Riverside
Meghan Skaer
UC Davis
Affiliations for identification purposes only.

Cal-IPC News
Fall 2013 – Vol. 21, No. 3

Editors: Elizabeth Brusati and Doug Johnson
Cal-IPC News is published by the California Invasive Plant
Council. Articles may be reprinted with permission from the
editors. Submissions are welcome. Mention of commercial
products does not imply endorsement by Cal-IPC. We reserve
the right to edit all work.

Cal-IPC News Fall 2013

By Doug Johnson

s David Richardson and Anthony Ricciardi write in their recent ‘field guide” to
critiques of invasion science, there seems to be a growing “cottage industry of
criticisms” addressing the field (Diversity and Distributions 19: 1461-1567). Some of the
critiques are more useful than others. In their generally interesting compilation Invasive
and Introduced Plants and Animals: Human Perceptions, Attitudes and Approaches to
Management (2013) editors Ian Rotherham and Robert Lambert, British environmental
historians, conclude that “…intervention in conservation practice hides behind a veneer
of pseudoscience and certainly challenges democratic processes.” As in many recent
critiques, this conclusion is based on an element of truth, but it overreaches the actual
reality in the field. Though they raise critical issues to address, such critiques understimate the degree to which these issess are already being examined.
This issue of Cal-IPC News touches on one of these topics: the complex interactions
between native and non-native species. Do naturalized non-native plants support native
wildlife? (Sometimes.) Are they an adequate replacement for the native plant species
with whom California wildlife evolved? (Rarely.) In the real world, do managers need to
evaluate potential wildlife benefits of invasive plants when determining realistic conservation goals? (Of course.) Though the underpinnings of the field provides rich intellectual fodder, critics should make sure they are well versed in the ever-dynamic state of
the discipline so that their criticism is ultimately constructive, not simply contrarian.
Managing invasive plants, like all conservation, is part science and part societal
values. We pass laws to protect endangered species because we deem it to be the moral
and prudent thing to do. Then science helps us figure out how to do it. Unavoidably,
communication mixes science and values. The term “invasive” has a scientific meaning, and also carries significant cultural meaning. As Brendon Larson describes in his
Metaphors for Environmental Sustainability: Redefining Our Relationship with Nature
(2011), words take on a life of their own in society’s “metaphoric web” and it is difficult, but essential, for conservationists to tend their terms over time.

On the cover…
Natural resource managers continue to explore the complex interactions between native
wildlife and non-native plants. Non-native plants listed by Cal-IPC as invasive are
assessed to have significant negative ecological impact on native California ecosystems
and wildlife. But that does not mean that
wildlife have no use for these plants. As Brian
Murphy’s cover photo shows, some native
pollinators do visit some invasive plants. Don
Weden caught the ground squirrel at right
chowing on yellow starthistle at Rancho San
Antonio in Santa Clara County (winning 1st
place in our 2013 Photo Contest). Cal-IPC’s
recent “Climate-Smart Management” workshop
asked participants to consider ecological services offered by top weeds of concern. Weighing
such information will become increasingly
important as land stewards design management
approaches to meet long-term conservation
goals in an age of great environmental change.

Cal-IPC Updates
2013 Symposium goes on despite
federal shutdown. Adaptive management
was in full swing as speakers and attendees
from federal agencies were not allowed
to participate in the 22nd annual CalIPC Symposium, held Oct. 2-5 in Lake
Arrowhead. See page 6.
Cal-IPC posts new climate adaptation
webpage. Following on the “ClimateSmart Land Management” workshop held
at the Symposium, Cal-IPC has posted
workshop materials and other resources
on adapting natural resource management
to climate change. www.cal-ipc.org/ip/
climateadaptation
Tahoe Nature Fund will support
regional strategy in the north Sierra.
The new grant complements existing
funding for regional prioritization in the
region stretching from Placer County to
Plumas County. Cal-IPC will work with
regional partners like the Truckee River
Watershed Council.
Military bases to plan with Cal-IPC.
The Dept. of Defense Legacy Program
will fund Cal-IPC to develop regional
invasive plant management plans with
resource managers at six installations in
California. www.dodlegacy.org/legacy
California CESU admits Cal-IPC. The
California Cooperative Ecosystem Studies
Unit (CESU) brings federal and state
agencies together with universities and
NGOs for research collaboration.
ucanr.edu/sites/CCESU
Coalition advocates for wildlife
programs. Cal-IPC joined1,600 organizations in signing a letter drafted by the
Teaming with Wildlife coalition urging
Congress to continue support for natural
resources programs such as the North
American Wetlands Conservation Fund
and the Forest Legacy Program. In July,
the House Interior, Environment and
Related Agencies Subcommittee eliminated funding for these programs for the
federal fiscal year that started October 1.
teaming.com/news/
Shasta-Trinity National Forest uses
CalWeedMapper for management
plan. The Shasta-Trinity is the largest
national forest in California. Their new

Wildland
Weed News
management plan focuses on eradication
targets and early detection and rapid
response for new sightings. calweedmapper.calflora.org/shf_priorities
New Board members. The Cal-IPC
Board of Directors welcomes Annabelle
Kleist (Capitol Impact), Virginia Matzek
(Santa Clara University) and Colleen
Murphy-Vierra (California Dept. of Food
& Agriculture). www.cal-ipc.org/about/
staff.php.

Other Updates
Invasive species a top threat to birds.
Over the last 500 years, invasives are responsible for the extinction of at least 65
bird species, and are a top factor in recent
avifauna losses, says a recently released
report on the “State of the World’s Birds”
by BirdLife International. www.birdlife.
org/datazone/sowb/pressure/PRESS2
California Congressman establishes bipartisan group on invasives. Rep. Mike
Thompson from northern California has
taken the lead in forming a Congressional
Invasive Species Caucus. Their first goal
is to pass legislationg adding quagga

mussel to the federal invasive species
list, a move strongly supported by the
governors of western states. mikethompson.house.gov/news/documentsingle.
aspx?DocumentID=342054
AB763 signed into law. The bill, sponsored by Cal-IPC to strengthen aquatic
invasive plant control in the Delta, passed
unanimously through the legislature.
www.leginfo.ca.gov
Plan to control invasive plants in the
Delta. The draft Bay Delta Conservation
Plan includes a 20-page section on
Invasive Aquatic Vegetation Control, in
line with the goals of AB-763. baydeltaconservationplan.com Section 3.4.13.
Invasive bamboo on the horizon?
Researchers determined that five of
seven bamboo species tested from East
Asian coniferous forests are shadetolerant enough to spread in shady Pacific
Northwest forests. link.springer.com/
article/10.1007%2Fs10530-013-0434y#page-2
Online library of invasive plant articles.
With hundreds of articles in a searchable
database, TechLine Invasive Plant News is
designed for “sharing innovative research,
success stories and tips with invasive plant
managers.” techlinenews.com
…continued page 14

New Training DVD from Cal-IPC!

“Best Management Practices for
Preventing the Spread of Invasive Plants”
This 42-minute training video
presents important strategies for
preventing the accidental movement
of invasive plants, avoiding soil and
vegetation disturbance, planning
ahead for prevention, and promoting
organizational awareness of invasive
plants. Suitable for natural resource
managers and those managing
transprotation and utility corridors.
Available for $10 plus tax and
shipping. See trailer and order at
www.cal-ipc.org/shop.

Cal-IPC News Fall 2013

Controlling mayweed chamomile to
help endangered terns

California least tern, a federally endangered species, hovers above invasive mayweed chamomile
(Anthemis cotula) looking for a nest site. Photo
by Juan Benjuama, wildlife volunteer.

By David L. Riensche, Douglas A. Bell
and Cliff Rocha, East Bay Regional Park
District; Sara A. Lockett, Northern Arizona
University; Cody A. Newell, University of
Idaho; Rick Miller, Dow AgroSciences LLC;
and Bill Nantt, California Department of
Transportation

he California least tern (Sternula
antillarum browni) is a migratory
species, nesting from Baja California to
the San Francisco Bay. Terns establish
nesting colonies on sandy soils with little
vegetation along beaches, lagoons, and
bays. Nests are shallow depressions lined
with shells or other debris. Least terns
often have two distinct waves of nesting
between mid-April and late September.
The California least tern was listed as a
federally endangered species in 1970 and
as a state endangered species in 1971 due
to a population decline resulting from
loss of habitat, disturbance of nesting

Cal-IPC News Fall 2013

sites, and predation by domestic and
wild mammals. Loss of suitable habitat is
known to force species to breed in higher
densities or in suboptimal areas that may,
in turn, increase the risk of predation.
Our study site is known as Island
Five within a brackish water marsh of
the Hayward Regional Shoreline on San
Francisco Bay. Island Five is one of 15
islands created within a man-made marsh
system. This island was restored by 4,100
citizen-scientists who have placed filter
fabric, moved 175 tons of sand/oyster
shells to create nesting substrate, removed
vegetation by hand, and monitored terns
and their potential predators.
The Hayward Regional Shoreline
Marsh system provides habitat for more
than twenty nesting waterbird species.
The four dominant shorebirds nesting at Island Five with the California
least terns are the American avocet
(Recurvirostra americana), black-necked

stilt (Himantopus mexicanus), killdeer
(Charadrius vociferous) and western
snowy plover (Charadrius alexandrinus
nivosus), a federally threatened species.
The site is managed by the East Bay
Regional Park District (EBRPD), a
two-county special district in Alameda
and Contra Costa Counties. Since
2001, EBRPD has aimed to enhance
and manage a successful California least
tern colony at the Hayward Regional
Shoreline, while increasing public awareness and involvement for the protection
of endangered species.
Invasive plants are a major threat
to many wild bird species. The rapid
colonization of invasive plants can result
in substandard nesting habitat. Due to
its nesting preference for open substrate,
the California least tern is vulnerable
to the spread of vegetation that can
quickly colonize its nesting habitat.
From 2009-2011, mayweed chamomile

Sara Lockett and Cody Newell conduct
California least tern nesting surveys on
a weed-free island during summer 2013.
Photo by David Riensche.
(Anthemis cotula), a common weed from
Europe, became the dominant plant cover
on Island Five, creating a monoculture
and confining terns to subpar nesting
sites. The spread of this weed encouraged
waterfowl such as gadwall (Anas strepera),
mallard (Anas platyrhynchos), and cinnamon teal (Anas cyanoptera) to nest on

the island, which we believe drew red fox
(in 2009) and raccoon (in 2011) to swim
to the island and attack duck, shorebird
and tern nests. The combination of
limited nest site availability and increased
predation possibly led to the observed
reduction in reproductive success for the
terns in 2009 and 2011.
A partnership between EBRPD,
Caltrans, and Dow AgroSciences formed
in 2012 to address the rapid vegetation
growth and cultivate ideal nesting habitat
for the least tern. Dow AgroSciences contributed a combination of Milestone®,
Capstone®, Rodeo®, and Dimension®
specialty herbicides to inhibit the growth
of vegetation at the site. The combination
of herbicides was used at the recommendation of local pest control advisors and
has been proven to be “practically nontoxic” in dozens of laboratory tests and
field studies. The herbicides were carefully
applied by Caltrans specialists during the
late winter, prior to the terns’ arrival in
the spring. The treatments resulted in
a major decrease in vegetation. Results

Progress removing Algerian sea lavender
by Mike Perlmutter

lgerian sea lavender (Limonium
ramosissimum) is an invasive plant
growing in intertidal areas around
San Francisco Bay, as well as along the
coast from San Luis Obispo to San
Diego. The Bay Area Early Detection
Network (BAEDN) identified it as a
priority target, and with funding from
the San Francisco Bay Joint Venture has
led work at sites in Albany and Corte
Madera to see the efficacy of removal.
BAEDN’s 2013 work party on the
Albany shoreline (northern Alameda
County) took much less time than in
the past, and the progress was clear. The
first effort in 2011 took 40 volunteer
hours from the Friends of Five Creeks, a
local watershed group, to hand-remove
this infestation. The patches were
dense, with many seedlings establishing
underneath mature flowering plants.
Followup this year took 18 volunteer
hours to remove all the plants, totaling
3 large bags. The timing was perfect, as

plants were bolting, but not flowering,
therefore easy to see and pull without
risk of seed spread. Each year there have
been fewer plants, and the plants are less
mature and require less time to remove.
Formerly dense Algerian sea lavender
patches are filling back in with native

from a line intercept method showed that
vegetation cover in 2007 was 30% (height
of 24 cm), but vegetation cover reached
90% (height of 30 cm) in 2011. This
three-fold increase in cover was curtailed
after the application of herbicides, and in
2012 vegetation cover was less than 10%
(height of 23 cm).
In the two breeding seasons since the
herbicide treatment was applied, the terns
have reacted positively to the decrease in
vegetation. During the 2012 breeding
season, there were 189 incubated nests
at the site, producing a total of 228
chicks. In the 2013 season, the colony
experienced an amazing 95% hatching
success rate and produced upwards of 118
fledglings. The site is now the second
largest California least tern colony north
of Ventura County. Thanks to action
from this partnership to reduce mayweed
chamomile, the Hayward Regional
Shoreline is now a prime nesting site for
this endangered species.
Contact David Riensche at driensche@
ebparks.org.
marsh vegetation.
In Corte Madera volunteers from
Marin Audubon, Marin County Parks,
and San Francisco State have removed
plants, but been unable to get 100%
of the plants each year. Plant size has
been decreasing, though, and additional
resources could knock this population
out. These pilot efforts show the potential
for a comprehensive Bay-wide program to
succeed if funding can be secured.

Cal-IPC News Fall 2013

2013 Symposium in
Lake Arrowhead

“…another great Symposium! What amazes me is how
progressive Cal-IPC is. You are providing land managers
with critical information not just about invasive species
but relevant ecological restoration topics. I learned more
about California ecology and how to make smart future
land management decisions at the Cal-IPC conference
than I have at any other event in recent years…”
~Cindy Roessler, Midpeninsula Regional Open Space District

Top: Field trippers on the San Bernadino Mountains tour. (Photo by Stacy Gorin. All other photos by Drew Ready.) Above
left: Discussion at the poster session, which included six entries in our student contest. Above right: Sponsor booths lined the
hallways with information about their organizations. Opposite, clockwise from top left: Sixty entries were submitted to our
photo contest, including this shot by Tori Bohlen showing Mills College students pulling French broom seedlings in Tiburon.
Naturalist Laura Cunningham gave our keynote address on her book A State of Change: Forgotten Landscapes of California.
We tried a different format for this year’s raffle and auction, and the drawing got wild! Ken Moore runs a tool tailgate sharing
lessons learned during his years of experience. Cal-IPC board president John Knapp, on right, presents the 2013 Golden Weed
Wrench Award to James Law of the Santa Ana Watershed Association.

Cal-IPC News Fall 2013

Congratulations to: Jason Giessow (Jake Sigg
Award for Dedication and Vision); James Law
(Golden Weed Wrench Award, see below),
Christy Boser, The Nature Conservancy, and Kate
Faulkner, National Park Service for the California Islands BioSecurity Program (Policy Award);
Josh Volp, Orange County Conservation Corps
(Ryan Jones Catalyst Award); Southern California Mountains Foundation (Organization of the
Year); Student Papers: Chelsea Carey, UC Merced
(1st); Justin Valliere, UC Riverside (2nd); Bridget
Hilbig, UC Riverside (3rd); Student Posters:
Megan Engel, CSU San Bernardino (1st); Daniela
Bruckman, UC Irvine (2nd); Madison Hoffacker,
Chapman University (3rd).

Presentations and awards posted at www.cal-ipc.org/symposia
Cal-IPC News Fall 2013

Successful Spanish broom control in San Diego
By Robert A. James, Caltrans, San Diego

panish broom (Spartium junceum),
native to the Mediterranean region
and Canary Islands (McClintock 1979), is
a well-known invasive shrub throughout
much of California. It is rated by the
California Department of Food and
Agriculture as a Class C pest species and
by Cal-IPC as having “high” invasiveness
potential. Spanish broom has been a
control focus for many years in the state
(Bravo 1985). The USDA Forest Service
has recently undertaken removal projects
in the San Bernardino and Cleveland
National Forests with some success in
Southern California, particularly using
the herbicide triclopyr (L. Criley, USDA
Forest Service, pers. comm.).
Leblanc (2001) recommended
controlling brooms, including Spanish

broom, using an integrated pest management strategy that can include application
of glyphosate or triclopyr. Basal bark
herbicide application has been attempted,
but retreatment has been found to be
needed (Neill 2005). Research on effective physical and chemical control was
done in Argentina (Sanhueza and Zalba,
2012) with picloram also identified as an
effective herbicide, applied to cut stumps.
However, picloram does not adhere to soil
and has been found in groundwater (EPA
2012).
In mid-2012, an infestation of about
200 plants was identified for control by
Caltrans along both sides of State Route
67 (post miles 16.5-19) in rural northern
San Diego County, between the City of
Poway and the community of Ramona.
Plants were first noted about
20 years ago, and have increased in number and extent
(M. Connelly, Caltrans, pers.
comm.).

Methods

State Route 67, Post Mile 17.4, north side, before
broom removal (March 2012) and after removal
(September 2013).

Cal-IPC News Fall 2013

An initial cut-stump treatment was done with glyphosate (Roundup®, 50% a.i.,
water dilution) in May-July
2012. Above-ground biomass
was left in place where it did
not pose a safety concern for
motorists, and was allowed
to discompose. Triclopyr
(Garlon 4 Ultra®, 15-30%
a.i., water dilution) was used
for follow-up (and some
new) cut-stump control,
beginning in fall 2012.
Emergent broom plants were
hand pulled when possible,
or cut near ground level and
treated with triclopyr. A
second round of follow-up
surveys and control efforts
was done in July-August
2013, also using triclopyr.

Results
Over 95% of the plants were eliminated one year after initial control. However,
noticeably improved results were obtained
when the switch to triclopyr was made;
there were fewer resprouting stumps
requiring subsequent treatment (<10%).
Germinating broom, with their
photosynthetic stems, nicely contrasted
against dried grasses and other forbs
in late summer, making broom hand
removal easier and more thorough.
The distribution of emergent broom
was patchy and limited. No significant
erosion was observed. Native species such
as buckwheat (Eriogonum fasciculatum)
and mugwort (Artemisia douglasiana)
have filled in some of the areas previously
covered by broom; this ecological recovery
was also noted by Bravo (1985).

Summary and Conclusions
These results demonstrate that
substantial control is possible with
focused, correctly timed initial efforts,
and conscientious follow up. Use of
triclopyr allows for effectiveness without
the potential for adverse environmental
effects to water quality that can occur
with picloram.
I recommend application of triclopyr
to cut stumps in early summer. Leaving
the root system in place has the additional
environmental benefit of minimizing
soil erosion, especially on slopes or other
erodible soils. Follow up control must be
completed the next summer on the limited number of stumps that will resprout.
At least two follow up visits should be
completed in June and September one
year after initial treatment to identify
stumps that may resprout at different
times during the growing season.
Any germinating plants discovered
during follow up visits should be pulled
by hand, if possible, or chemically treated
as described above. Recognizing germinating broom is essential to control success,
and reduces needed follow up work, as
well as herbicide use. Recovery of native
vegetation will lead to increased shading

and ecological resilience, which should
also have the benefit of reducing habitat
suitability for broom (Moore 2011).
Since related Scotch broom is known
to have a seed bank that is mainly persistent for the first two years (in Leblanc
2001), the treatment area should be
annually monitored for a total of at least
two subsequent summers (i.e., for a total
of three years after initial control). This
crucial follow up will allow for removal
of any germinating Spanish broom when
individual plants are small and the
recurrence is limited in the area. It is not
known for certain how persistent the
Spanish broom seed bank is, so a different
monitoring period may be warranted
based on subsequent observations
In speaking with nearby residents
while control efforts were underway,
several people were unaware of the hazards
of broom, and appreciated the aesthetic
benefits the plant offered as part of the
semi-arid landscape. Any control program
should recognize this cultural perspective and educate stakeholders about the
adverse environmental impacts of the
species; this will help ensure program
support and potentially allow the efforts
to be extended to private lands.
By following these straightforward
approaches, scaled to available resources
and the areas of concern, the challenge of
controlling Spanish broom can be won.
Special thanks to Caltrans Maintenance
staff, especially Kathlene Manini, Donald
Parker, and Daniel Schmidt. Contact the
author at robert.a.james@dot.ca.gov

References
Bravo, L.M. 1985. We are losing the war against
broom. Fremontia 12(4):27-29.
EPA. 2012. Basic information about picloram in
drinking water. Retrieved from water.epa.gov/drink/
contaminants/basicinformation/picloram.cfm
Leblanc, J.W. 2001. Getting a handle on broom:
Scotch, French, Spanish, and Portuguese brooms in
California. Univ. of Calif. Agriculture and Natural
Resources, Publication 8049.
McClintock, E. 1979. The weedy brooms: where did
they come from? Fremontia 6(4):15-17.
Moore, K. 2011. Long-term broom management.
Cal-IPC News 19(3):6-7.
Neill, B. 2005. The basal bark method of applying
triclopyr herbicide. Cal-IPC News 13(1):8-9.
Sanhueza, C. and S.M. Zalba. 2012. Experimental
control of Spanish broom (Spartium junceum) invading
natural grasslands. Management of Biological Invasions
3(2):97-104.

Staying “on label” in tidal waters
by David Thomson, San Francisco Bay Bird Observatory, Habitats Program

he Fall 2012/Winter 2013 issue of
Cal-IPC News contained an article
entitled “Special concerns near aquatic
habitats” by Drill and Trumbo. The
article presents a good review of herbicide
concerns with most aquatic habitats –
except for tidal waters. This is a situation
that applies to all of us managing intertidal invasive plants like Spartina hybrids
and Limonium ramosissimum.
In order to stay “on label” with some
herbicides you cannot spray “intertidal
areas below the mean high water mark.”
For example, the Telar (XP/XD) labels
state: “Do not apply directly to water, or
to areas where surface water is present,
or to intertidal areas below the mean
high-water mark.” But what exactly is the
mean high-water mark?
According to the US EPA the
“mean high-water mark” separates
intertidal coastal and estuarine areas that
are exposed during low tide but covered
during high tide from adjacent terrestrial
areas. EPA says the definition varies by
state, but in general it’s “the line on the
shore established by the average of all high
tides. It is established by survey based on
available tidal data (preferably averaged
over a period of 18.6 years because of the
variations in tide). In the absence of such
data, less precise methods to determine
the mean high-water mark are used, such
as physical markings, lines of vegetation
or comparison of the area in question
with an area having similar physical

characteristics for which tidal data are
readily available.” See the diagram below
on tidal waters.
Unfortunately, detailed tidal data are
usually not available for most sites, and
the alternative methods of using physical
markings or lines of vegetation can be
unclear, even to those of us who have
spent years mapping coastal wetlands.
California’s State Water Resource
Control Board (SWRCB) has a new draft
wetland policy that appropriately defines
the upper tidal boundary: “For all tidal
landscapes, shallow surface water is any
portion of the tidal prism that is bounded
by the local Mean Lower Low Water
(MLLW) datum and the local maximum
tide height as adjusted for the current
tidal epoch.”
However, this still relies on tidal data
that is not generally available for most
sites. I encourage the SWRCB and other
regulatory agencies to work on providing
more specific guidance on how the label
term “mean high-water mark” should be
determined by herbicide applicators.
Especially with the added complexity
of climate-induced sea level rise, those of
us working to protect intertidal habitats
need even more straightforward and
effective methods for assessing where
herbicides can and cannot be used on our
work sites.
Contact the author at d.x.thomson@gmail.
com.
Diagram: US Army Corps of Engineers

Cal-IPC News Fall 2013

Retail nurseries get recognition and training from PlantRight
By Jan Merryweather, Sustainable Conservation

ith the launch of its free Retail
Nursery Partnership program,
PlantRight becomes the go-to resource for
California nursery retailers interested in
building expertise on ornamental invasive
plant issues and opportunities. It’s one
more way for retailers to demonstrate,’We
Care!’ when it comes to selling regionally
appropriate and environmentally-friendly
plants.
Nurseries joining the program agree
to not sell plants listed by PlantRight as
invasive, and to educate their customers
and staff about the problems caused by
invasive plants.
PlantRight is a project of the
California Horticultural Invasives
Partnership (Cal-HIP), a coalition of

environmental and horticultural industry
groups. The nonprofit group Sustainable
Conservation in San Francisco oversees
the partnership. Cal-IPC has been a
member of the coalition since its inception in 2004.
PlantRight’s training materials and
science-based educational content are
easy-to-access, practical, and available 24/7, so that even the busiest
garden center professional can benefit.
Nurseries can learn more about this free
program by visiting: www.plantright.org/
create-your-plantright-account.
If you like the sound of this program,
and would like to see more PlantRight
nursery partners in your area, take a
moment to introduce us to your local

garden center. Send an email with your
local garden center’s name and contact
information to PlantRight@suscon.org.

“PlantRight training allows us to
make responsible purchasing choices,
share our philosophy with customers, and offer reasonable alternatives
to popular invasive species. I would
encourage all garden center owners
and managers to participate in this
partnership.”
Charlie Keutmann, Owner, The
Garden Company (Santa Cruz)
“When PlantRight approached
Sloat Garden Center, joining forces
was a slam dunk. PlantRight’s efforts helped solidify and train our
team with a singular, cohesive
message that can easily be communicated to our customers through
signage, handouts, on-line presence
and team member knowledge.
Retailers across the country should
embrace these types of efforts to
educate our customers, helping
them make more informed and
responsible decisions.”
The Garden Company in Santa Cruz
proudly displays its PlantRight window
decal.

Cal-IPC News Fall 2013

Dave Stoner, President/CEO, Sloat
Garden Center, Inc. (Nine locations
in the San Francisco Bay Area)

Cal-IPC recently reprinted two of
our “Don’t Plant a Pest!” brochures
featuring invasive ornamental plants
to avoid as well as suitable landscaping
alternatives. The San Francisco Bay
Area brochure and the statewide Trees
brochure are available once again.
They are great educational resources
for plant sales or garden tours. We
can provide up to 10 copies for free;
request them by emailing info@
cal-ipc.org. Larger quantities may be
ordered from www.cal-ipc.org/shop.

Tracking eradication progress
By Vince Guise, Contra Costa County Agricultural Commissioner

ocumenting weed work in a manner
that shows progress toward our goals
is a challenge that all weed workers face,
especially when we are aiming for eradication. Here are some of our practices and
experiences from Contra Costa County.
We have 17 noxious/invasive weed
species that we deal with as a department.
In our program we are trying to eradicate
15 of the 17 species. It takes persistent
and dedicated field work to get rid of
some of these species. Due to limited
resources and other considerations we are
trying to manage the other two species,
perennial pepperweed and pampas grass,
by treating satellite infestations found in
new areas and some leading edge areas.
We document the work that we
perform on a property-by-property
basis and have been doing so for the 34
years of our program. Some properties
are small, 5- or 10-acre ranchettes, and
others are ranches or regional park open
space areas that are well over 1,000 acres.
We document each weed species treated,
the date of treatment, the treatment
type, the name and amount of concentrated product if herbicides are used, the
person(s) that performed the application
on the property, the gross acres surveyed
and the net acres treated. We don’t track
separately the individual infestations
of a species on the same property. We
do track separately the different species
treated on each property. We treat all of
the targeted species each year with a goal
of not allowing new seed to set.
Our main indicator of progress
on a property is net acres treated over
the years. Eventually we will come to
eradication of the species on the property,
after three years of no detected plants
of the targeted species on the entire
property. One of the problems with this
is that it does not take into consideration
the multiples of small infestations that
may have been eradicated from the
property previous to the overall eradication. This all-or-nothing property-byproperty approach does not fully show the
progress that we have made in eradicating

individual populations, though we generally can show an overall decline in net
acres on the property.
One idea that is sometimes used is
“eradicating to seed bank,” meaning that
all plants are treated or removed to where
no new seed is produced. This would
help to show short-term progress though
real eradication can be many years down
the road. If eradication to seed bank is
accomplished from year to year (as in our

Observed seed bank longevity:
Artichoke thistle: 15-20 years
Purple starthistle: 8-12 years
Red sesbania: 8 program years so far
and we expect 30+ year seed life
Barb goatgrass: 3-4 years
Perennial pepperweed: 3-4 years (less
if the area is treated with TelarTM )
Russian knapweed: 3-5 years
White horsenettle: 12 years
Smooth & woolly distaff thistle: 6-10
years
Kangaroothorn: >8 years
Pampasgrass: 1-2 years
Japanese knotweed: Does not produce
seed in our area, but deep rooted stolons
take 2-3 years with Imazapyr
Japanese dodder: Also does not
produce seed in our area but small remnants that are missed when host plants
are removed can keep the infestation
going until they are detected. Usually
2-3 years maximum.
program) then it is a matter of persistence
until the seed bank is finally depleted and
true eradication is achieved.
It is very difficult to get good information on seed bank life in field situations.
We have asked the CDFA Seed Botanist

to tell us the seed longevity of each. He
was not able to find good information.
We have also found information in books
written by well-respected authors to be
different than what we find in the field.
The sidebar lists the seed bank longevity
that we have observed for the plants we
are working on.
Another factor is missed plants. This
extends eradication time due to new seed
introduced into the soil. And I strongly
disagree with any “one acre or less”
eradication thought. If you don’t get it all,
the plant can and likely will come back.
Most of these species seem to have a
“breaking point” when net acres fall off
significantly. With artichoke thistle, for
example, it is 3-5 years. Populations of
some species bounce around for a few
years before reaching a breaking point.
Purple starthistle goes up and down for
6-7 years before dropping off to a low
level. However we have noticed in the
last two years since we started using
MilestoneTM on artichoke thistle and
purple starthistle that these species crash
to lower levels much faster than with
materials we used before. It seems that
new germinating seed of these species may
be sensitive to low residual levels in the
soil since this effect seems to carry over
from year to year.
Eradication depends on the tools
available, the dedication and persistence
of individuals, and the structure of the
program. One of our success stories s is
a 1,060-acre ranch that was first treated
near the beginning of our noxious weed
program. In 1983, 22 net acres of artichoke thistle were treated by air. Besides
dense patches, there were also scattered
individual plants throughout this property. Over the years the net acreage on this
ranch has diminished to the point that
we now count individual plants. We had
42 plants this year and expect there will
be zero plants in the next 2-3 years. We
have had many properties that followed
the same pattern with some reaching total
eradication. This goal should be the gold
standard for our work, but it requires
steady funding and attention, which we
have been fortunate to have in our county.
Contact the author at Vince.Guise@
ag.cccounty.us.

Cal-IPC News Fall 2013

Prescribed grazing for invasive plant control on rangelands
By Josh Davy, UC Farm Advisor, Tehama,
Glenn, Colusa Counties, Kenneth Tate, UC
Range Specialist, and Leslie Roche, Post-doctoral Researcher at the UC Davis Rangeland
Watershed Lab

ost herbicide weed control methods are good at initial control, but
can lack long-term weed management
effectiveness if weeds are allowed to reestablish. Grazing is a tool that can offer
an opportunity to suppress herbaceous
weed populations on rangelands over a
longer term. However, grazing should
be thought of as a weed “management”
tool because grazing does not usually
control every plant treated. Instead,
grazing can be used to restrain the prolific
seed production of annual weeds or root
carbohydrate storage of perennial weeds.
Depending on the situation, grazing and
herbicide weed control methods can be
used independently or in cooperation.
There are important factors to keep
in mind when approaching a grazing
management option for weed control.
Unlike herbicides that can make an immediate impact on large weed populations
regardless of soil and weather conditions,
grazing is more complicated and dependent upon site-specific conditions.
Also, herbicide control entails less
physical infrastructure such as fencing and
does not require a skilled cowboy to keep
livestock fenced on the targeted area.
Finally, livestock are bred primarily to
produce food and fiber. Although using
livestock for weed control is a double bonus, it means that maintenance of animal
nutrition demands while “meating” weed
management goals is very important.
Factors such as running out of livestock
drinking water or a late season reduction
in forage quality before optimal defoliation levels are hit can impact weed control
success from year to year. It may also
require thought about the class of animal
used for targeted grazing specific weeds.
For example, mature dry cows may serve
better for consuming low quality forages
than growing yearling cattle or lactating
cows.
Three main strategies exist for weed

Cal-IPC News Fall 2013

Fenced cattle in medusahead timed grazing research trial. Photo by Josh S. Davy
management on rangeland. These include:
1. Exhaust the root reserves of annual
plants through defoliation as soil
moisture is being depleted. This inhibits the plants’ ability to make seed
for subsequent-year germination.
2. Repeated grazing of perennial weeds
just prior to the onset of dormancy.
Defoliation of plants at this time
exhausts root reserves required by
plants during the dormant period and
entering the next growing season.
3. Remove thatch and open up the
canopy to allow desirable plants to
establish. This is mostly helpful with
weeds that create a monoculture such
as medusahead. Published scientific
support for this strategy is limited.
The first two strategies are the essential
components for reducing weed density in
a target area. The key to implementing
the first two strategies is timing, timing,
and timing of defoliation. Target weeds
need to be heavily defoliated as soil moisture is depleted at the end of the growing
season. Without moisture to recover,
defoliated plants senesce with little or no

reproduction and have a reduced chance
of surviving dormancy. If adequate
moisture is available, the plants are able to
recover from grazing.
Clay soils with high water storage potential, or late growing-season rains after
grazing ends, can hinder the effectiveness
of grazing. Deep-rooted plants are better
able to tap soil moisture than shallow
rooted plants, usually making a single
target grazing more successful on shallower rooted annual plants than biennial
or perennial weeds. This can be positive
if a manager’s goal is to lessen the impact
of invasive annual grasses on deep-rooted
native perennial grasses.
Examples of successfully managing
weed populations exist. The following three examples depict what we have
learned from targeted grazing on annual,
biannual, and perennial plants. Many
more published examples exist.
• Heavy defoliation of medusahead (Taeniatherum caput-medusae) in late spring
as plants are entering the bolt stage has
proven very successful in limiting seed
production and subsequent year’s plant
density (DiTomaso et al. 2008).

• Yellow starthistle (Centaurea solstitialis)
required multiple heavy grazing sessions late in the season to reduce seed
production due to the plant’s deep roots
(Thompsen et al. 1993).
• McKell et al. (1966) found repeated
defoliation of hardinggrass (Phalaris
aquatica) during spring prior to dormancy
could cause plant death. Fundamentally
showing deep-rooted perennial plant control is possible using repeated defoliation
as a strategy.
Exciting new research at the Sierra
Foothill Research and Extension Center

led by the California Rangeland Watershed Laboratory is examining the longterm effects of four grazing treatments.
The lab has completed the first year of
implementing treatments of seven-month
continuous grazing, four-month fall and
spring grazing, four-month fall and spring
targeted grazing, and winter-only grazing.
The lab has implemented the project at
a ranch scale (over 1200 acres, using over
360 cattle) and is monitoring multiple parameters including yearling cattle production, invasive and native plant responses,
and other ecosystem responses.

It is important to note that the “target
style” grazing strategies for weed control
described above are not the only way that
grazing can affect weed management. Any
defoliation of weed plants has an impact
on their subsequent seed production
or the amount of thatch accumulated.
Grazing can also have a positive effect on
the reduction of fire fuel loads. A grazing strategy with a moderate continuous
stocking rate does reduce weeds such as
medusahead and starthistle when compared to non-grazed areas. With this grazing scheme it may be that effects are not
seen on high rainfall years or years with
significant late growing season rainfall,
but effects may be seen during drought
years or years with an early end to rainfall.
As stated earlier, grazing treatments
rarely control the entire weed population.
Rainfall’s influence on a grazing treatment’s “perfect” timing can cause success
to vary from moderate to high between
years. Because of this, grazing should be
implemented only as a long-term weed
management strategy. Such moderate
single-season success in weed management
can compound over years into drastically
lower weed populations.

References
DiTomaso, J. M., G. B. Kyser, M. R. George, M. P.
Doran, and E. A. Laca. 2008. Control of medusahead
(Taeniatherum caput-medusae) using timely sheep grazing. Invasive Plant Science and Management. 1:241–247
McKell C. M., R. D. Whalley, V. Brown. 1966. Yield,
Survival, and Carbohydrate Reserve of Hardinggrass
in Relation to Herbage Removal. Journal of Range Management. 19(2): 86-89

Medusahead at the proper phenological stage to begin a targeted grazing treatment.
Photo by Josh S. Davy

Impacts of native vs. exotic
grassland vegetation
By Valerie Eviner, Joanne Heraty, Jill Baty,
Carolyn Malmstrom, and Kevin Rice, UC
Davis Dept. of Plant Sciences
[Abstract from poster presented at the 2013
Cal-IPC Symposium]
California’s grasslands have been dominated by annual exotic grasses for the
past 200-300 years. More recently, newer

invasive grasses have become prevalent,
such as medusahead and barbed goatgrass.
Control of these newer invasive grasses, or
restoration of natives is not possible in all
impacted areas, due to the broad extent
of these invasions. Ecosystem services are
a potential criteria to prioritize areas for
restoration and weed control.
We planted plots consisting of three
community types: naturalized exotic
species (that have dominated California’s
grasslands for 200-300 years), invasive
weeds (goatgrass and medusahead), and

Thomsen C., W. Williams. M. Vayssiéres, F. Bell, and
M. George. 1993. Controlled grazing on annual grassland decreases yellow starthistle. California Agriculture.
47(6):36-40. DOI: 10.3733/ca.v047n06p36

native species (common mix of species
used for restoration in California’s Central
Valley). After 3 years,we assessed the impacts of these vegetation types on multiple
ecosystem services. When comparing
natives to naturalized species, natives
increased soil nitrogen availability, and
were much better at suppressing invasive
weeds. However, the naturalized species
plots provided better erosion control,
mitigation of soil compaction, water qual…continued page 14

Cal-IPC News Fall 2013

…continued from page 13
ity, and soil water storage. This suggests that
restoration of natives will be most beneficial
in areas with high invasive weed pressure, but
could be detrimental in areas where erosion,
compaction, and water quality are of concern.
Invasion of noxious rangeland weeds into
the naturalized community did not enhance
any ecosystem services, and greatly decreased
palatable spring forage quantity. However,
there is a tradeoff between invasive weeds
and native species. Invasion of noxious weeds
into native communities decreased spring
forage availability and decreased soil nitrogen
availability, but enhanced soil water storage,
compaction alleviation and water quality. This
suggests that sites that are less vulnerable to
soil degradation would be best to prioritize for
invasive weed control.
While the impacts of invasive grasses on
California’s flora are an important criterion
for restoration and weed control, it is not
possible to manage all invaded areas. Thus,
prioritization of sites for management should
consider that some of these invasive grasses are
improving soil conditions and water quality.

Thank you 2013 Symposium Sponsors!
Dow AgroSciences

PLATINUM
ACS Habitat Management
California Association of Local Conservation Corps
Pacific Gas & Electric Company

Sacramento Municipal Utility
District
State Coastal Conservancy
GREEN
American Conservation Experience

GOLD
The Nature Conservancy
USDA Forest Service
SILVER

California Association of Resource
Conservation Districts
California Native Grasslands
Association

Center for Natural Lands Management Dendra, Inc.
Chapman University, Schmid College Dudek and Habitat Restoration
of Science & Technology
Sciences, Inc.
Hedgerow Farms
Garcia and Associates
National Park Service, California
Exotic Plant Management Team
Santa Ana Watershed Association

Irvine Ranch Conservancy
RECON Environmental/
RECON Native Plants, Inc.
Resource Conservation Partners

BRONZE
California Native Plant Society

SERCAL

Contact the author at veviner@ucdavis.edu.

Weed Control in Natural Areas
in the Western United States
Published in 2013
by the University
of California’s
Weed Research and
Information Center,
with 15 contributing
authors.
The manual presents
detailed information
on biology and
control methods for
340 species found
in thirteen western
states. Includes tables
summarizing chemical
and non-chemical
control options.

$37.00 plus tax and shipping from
544 pages with photos. the Cal-IPC online store.

Order at www.cal-ipc.org/shop
14

Cal-IPC News Fall 2013

Wildland Weed News, cont’d…
Undergraduates help National Wildlife refuges. Eight
universities including UC Santa Barbara participated in a
combined seminar which compiled data on invasive plants
in nearby refuges, including habitat richness and evenness,
elevational range, native species diversity, refuge size, and
the regional pool of invasive species. Results were combined
for a continental-scale analysis. They found that patterns are
highly variable among regions, suggesting that management
strategies for invasive species are best formulated at the
regional level. Santa Barbara Independent, August 22.
Does it matter whether a plant is native? Dr. Mark Davis
of Macalester College and Dr. Daniel Simberloff of the
University of Tennessee-Knoxville debated when, if, and
how conservation biologists and managers should deal with
non-native species. A recording of “Native and non-native
species: How much attention should managers be paying
to origins?” is available at distancelearning.fws.gov/players/
con_sci.html.
Eucalyptus: friend or foe? The online science blog
for KQED public radio in San Francisco describes the
controversies surrounding removal of eucalyptus stands
in the East Bay. blogs.kqed.org/science/2013/06/12/
eucalyptus-california-icon-fire-hazard-and-invasive-species/

Thank You for Supporting our Work!
New and Renewing
Individual Members:

Organizational Members

Stewardship Circle ($1,000)
Peter Beesley, Grass Valley
Jason Casanova, La Crescenta
Peter Schuyler, Santa Barbara
Steve Schoenig, Davis
Jake Sigg, San Francisco
Champion ($500)
Edith Allen, Riverside
Paul Aigner, Lower Lake
Gary Gero, Los Angeles
Doug Gibson, Encinitas
John Knapp, Santa Barbara
Partner ($250)
Jutta Burger, Tustin
Frank Davis, Santa Barbara
Lynn & Rick Frame-Hoskins,
Mill Valley
Jason Giessow, Encinitas
Shawn Kelly, Oxnard
Dan Knapp, Los Angeles
Jean Schuyler, Santa Barbara
Kathy Welch, Truckee
Paul Ziemann, Riverside
Daniel Kellog, Gold Hill, OR
Lincoln Smith, Albany
Ann Howald, Sonoma
Mary Millman, Berkeley
Helen Conway, San Jose

ACS Habitat Management
California Association of Local
Conservation Corps
California Native Grasslands
Association
California Native Plant Society
High-school student Connor describes
weed projects at the National Children’s
Forest during the San Bernardino
Mountains field trip at the Symposium.

California Weed Science Society
Center for Natural Lands
Management
City of Walnut Creek
County of Lake Agricultural
Commissioner’s Office
DriWater, Inc.
Dudek and Habitat Restoration
Sciences, Inc. (HRS)
Forester’s Co-Op
Habitat West, Inc.
Hedgerow Farms
Inyo County Water Department
Mendocino Redwood Company
National Park Service – California
Exotic Plant Management Team
Pacific Gas and Electric Company
RECON Environmental /RECON
Native Plants, Inc.
Rocky Mountain Elk Foundation
Santa Ana Watershed Association
SERCAL
Shelterbelt Builders, Inc.
Sierra Foothill Conservancy
Southern California Mountains
Foundation
Sweetwater Authority
The Huntington Library
The Nature Conservancy
US Fish and Wildlife Service Inventory and Monitoring Program
USDA Forest Service

Organizational Membership:
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Cal-IPC News Fall 2013

Non-Profit Org.
U.S. Postage
PAID
Berkeley, CA
Permit No. 1435

California
Invasive Plant
Council
1442-A Walnut Street, #462
Berkeley, CA 94709
ADDRESS SERVICE REQUESTED

The WILDLAND WEED CALENDAR
Northern California Botanists
January 13-15
Chico
www.norcalbotanists.org
California Weed Science Society
January 22-24
Monterey
cwss.org

Northern Rockies Invasive Plant
Council
February 10-14
Spokane, WA
www.regonline.com/2014nripc

Invasive Weeds Awareness Day at the
Capitol
March 12
Sacramento
www.cal-ipc.org

Western Society of Weed Science
March 10-13
Colorado Springs, CO
www.wsweedscience.org

SERCAL
May 13-15
Santa Rosa
www.sercal.org

“If we really want to change people’s minds about invasive plants, I think we need to re-name
them… Himalayan blackberry could probably be called “ravening monsterthorn” without
anybody who is familiar with it complaining.”
– Ursula Vernon, “A Matter of Names”,
nativeplantwildlifegarden.com/a-matter-of-names/