CalEPPCNews
Protecting California’s Natural Areas
from Wildland Weeds
Vol. 11, No. 1, Spring 2003
Yes, Calla lilies. In Western Australia, which has a Mediterranean climate
similar to ours, Zantedeschia aethiopica is commonly known as arum lily.
It is also known as an aggressive invader of forests and forested wetlands.
This photo was taken mid-September (late winter) by John Randall of
The Nature Conservancy’s Wildland Invasive Species Program about 135
km south of Perth near the Tuart Forest National Park. What lessons in
prediction might we learn from invasives in other Mediterranean
climates? Our lead article from two Australian researchers addresses this
important issue.
Quarterly newsletter of the California Exotic Pest Plant Council
Inside:
Weed warning from
downunder!
Not just in the garden anymore:
Oxalis pes-caprae
Wal-Mart dumps pampas grass
Teaching teachers about weeds
From the Director’s Desk
Quick, what time of year do the rains come?
California
Exotic Pest Plant
Council
1442-A Walnut Street, #462
Berkeley, CA 94709
(510) 525-1502
www.caleppc.org
A California 501(c)3 nonprofit organization
Our Mission
CalEPPC works to protect
California’s natural areas
from wildland weeds through
research, restoration, and education.
Executive Director
Doug Johnson
dwjohnson@caleppc.org
Board of Directors
Joe DiTomaso (President)
UC Davis Weed Science Program
Steve Schoenig (Vice President)
California Dept. of Food & Agriculture
Mona Robison (Secretary)
UC Davis Weed Science Program
Becky Waegell (Treasurer)
The Nature Conservancy
Mike Kelly (Past President)
Friends of Penasquitos
Carla Bossard
St. Mary’s College
Matt Brooks
USGS Western Ecological Resource Center
Deanne DiPietro
Sudden Oak Death Research Project
Tom Dudley
UC Berkeley Dept. of Integrative Biology
Dawn Lawson
US Navy Facilities
For most people in the world, the answer would be, “Summer!” But for most Californians, the answer is, “Winter, of course.” Our “Mediterranean” climatic regime of hot
summer drought and winter rain is found over only 2% of the world’s landmass.
Besides California and the Mediterranean Sea area itself, three other regions have a
similar climate: Chile, the tip of South Africa, and western and southern Australia.
Because wildland weeds are often climate dependent, many of our invasives come from
these other Mediterrean climate regions—eucalyptus from Australia, brooms from the
Mediterranean, Cape ivy from South Africa, and Spartina densiflora from Chile, for
instance. Likewise, California natives can misbehave in other Mediterranean regions—
California poppies and Monterey pine, for instance, are invasive in Chile, Europe,
Australia and New Zealand. Of course we import weeds from other climatic regions,
and export to them as well, but there is a special ecological link between the world’s
Mediterranean climate zones when it comes to invasive exotics.
What are the implications of this? For one, plants that have proven themselves to be
invasive in one of these regions should be considered potentially suspect in the other
regions. In hopes of thwarting further invasions, such information can put us a step
ahead for potential invasives not yet established in one of these regions. Our cover
article addresses this very issue. The Australian authors examine how several of their
weeds (which are sold in nurseries here) might fare in California wildlands by using a
climatic model that assesses where a particular plant may be able to naturalize.
The link between Mediterranean climate zones also means that we need to work
together. The Australian article demonstrates one way in which we can join forces to
predict potential invasives before they get started. There are other effective ways to
collaborate. The International Broom Initiative’s efforts to develop biocontrols for a
family of brooms and gorse is a great example. By coordinating research among all areas
infested with broom—including California, Oregon, Washington, British Columbia,
Hawaii, New Zealand and Australia—and by working on Scotch, French, Spanish,
Portuguese and other invasive brooms together, the project is designed to accomplish
much more than could any one country working on any one plant. We need all the
efficiency we can get.
Carri Pirosko
California Dept. of Food & Agriculture
Alison Stanton
BMP Ecosciences
Scott Steinmaus
Cal Poly San Luis Obispo
Peter Warner
California State Parks
Bill Winans
San Diego County Watershed Management
CalEPPC News
Spring 2003 – Volume 11, Number 1
Editor: Doug Johnson, dwjohnson@caleppc.org
CalEPPC News is published quarterly by the California
Exotic Pest Plant Council. Articles may be reprinted
with permission from the editor. Submissions are
welcome. We reserve the right to edit all work.
From www.themediterraneangarden.org/climate/map.cfm
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CalEPPC News
Spring 2003
Wildland Weed NewsNewsNewsNewsNews
The Center for Invasive Plant Management (CIPM) in Montana has awarded
grants to three WMAs in California—
Butte County for water-milfoil control,
Yolo County for mapping sloughs and
roadside revegetation, and Lake county
for outreach and education. Online
applications for this year at
Members of the International Broom
Initiative presented the project at a
USDA-sponsored forum at their Albany
lab January 17. IBI is again working with
California’s congressional delegation to
submit a funding request for the lab to
research biocontrols for brooms and gorse.
Project partners from Oregon, Washington, Hawaii, British Columbia, Australia
and New Zealand advocating for the $1.4
million request point to the high ecological and economic costs of expanding
broom infestations and the need for a
cost-effective strategy that address these
infestations on a landscape scale.
Funding for CDFA weed programs has
been cut severely in the governor’s
proposed 2003/04 budget. When
combined with December’s cuts, this
latest cut chops the program by 50%,
severely reducing staff and operating
expenses in the Biocontrols and Weed &
Vertebrate programs. This cut will have
long-lasting impact on our ability to
control weeds in the state, and CalEPPC,
with partner organizations through the
California Invasive Weed Awareness
Coalition, is campaigning to have these
cuts reversed. Your voice can help in this
matter. To express your concerns, see
sample letter and information at
Congressman Hefley (R-CO) and Senator
Craig (R-ID) have reintroduced the
Harmful Invasive Weed Control Act,
which seeks $100 million a year until
2006 for local weed management groups
nationwide.
CalFlora, the much-used online botanical
database, closed shop February 1 due to
insufficient funding. Staff and volunteers
continue to pursue sources of stable
funding, with the goal of reopening as
soon as possible. Visit
for more information.
Save the date!
CalEPPC Symposium
October 2-4, 2003
North Tahoe
Conference Center
Board Changes
The CalEPPC Board of Directors
welcomes two new members—Carri
Pirosko of Redding and Deanne
DiPietro of Petaluma. Carri coordinates weed outreach in northern
counties for the California Department of Food & Agriculture, and is
keenly interested in education.
Deanne works with the Sudden Oak
Death Research Project at Sonoma
State. She has also been involved with
Team Arundo del Norte, and was
instrumental in developing the state’s
weed mapping handbook released last
September. Their experience and
energy will be a great addition to the
board!
At the same time, we extend our
gratitude to outgoing directors Carl
Bell of UC Cooperative Extension in
San Diego and Paul Caron of
CalTrans in Ventura for their dedicated work on the board over the last
two years. This was Carl’s second tour
of duty, and we greatly appreciated the
experience and insight he brought to
our strategic planning. Thanks!
Mule power. Britt Schumacher of the Tehama County Agriculture Department, riding
Charlie Horse, takes Brittany the mule into dry creek beds to spray arundo and
tamarisk. This spring he plans to use her for a small brush control project in steep
country that’s difficult to access. Britt got the trained mule from a successful weed
program in Idaho.
CalEPPC News
Spring 2003
3
Feature
Weed warning from downunder
The weed potential of selected South African plants
in cultivation in California
By Roderick P. Randal1 and Sandra G. (Sandy) Lloyd
Department of Agriculture, Western Australia, and
Cooperative Research Centre for Australian Weed Management
Reprinted from the proceedings of the
13th Australian Weeds Conference, held
Sept. 8-13, 2002, Perth, Western Australia.
H. Spafford Jacob, J. Dodd, J.H. Moore, eds.
Council of Australian Weed Science Societies
The authors propose that any plant
both: (a) native to one Mediterranean
climate region, and (b) a known weed in
at least one other, should automatically be
viewed as a threat to other Mediterranean
climate regions where it has not yet
naturalised, or has only a limited distribution.
The focus of this paper is on species
native to South Africa that are weedy in
the southwest of Western Australia
(Hussey et al. 1997) and available in the
horticultural trade in California. The
species selected are three geophytes—
bridal creeper (Asparagus asparagoides (L.)
W. Wight, Asparagaceae), watsonia
(Watsonia meriana (L.) Mill., Iridaceae),
and arum lily (Zantedeschia aethiopica (L.)
Spreng., Araceae)—and the small tree
taylorina or blue scurf pea (Psoralea
pinnata L., Fabaceae). Two Australian
species, bluebell creeper (Sollya
heterophylla Lindl., Pittosporaceae) and
Victorian tea tree (Leptospermum
laevigatum (Gaertner) F.Muell.,
Myrtaceae), are also discussed briefly.
METHODS
The native and naturalised distribution data for the three geophytes and
taylorina in both South Africa and
southwest Western Australia were
determined and analysed, with CLIMATE
predicting back to the world dataset to
determine just how much of California
would be suitable for establishment.
4
CalEPPC News
Spring 2003
CLIMATE is a predictive application
that uses long term meteorological station
data from within the known range of a
plant to determine similar climates within
Australia. Originally developed by the
Western Australian Department of
Agriculture, and based in part on
BIOCLIM (Nix 1986), this software can
also be used to analyse back to the large
global meteorological station data of
9,460 weather stations. In countries
where station coverage is very high, such
as the USA, good predictions can be
obtained.
CLIMATE uses 16 climatic variables,
all derived from long-term monthly
temperature and rainfall data. The output
parameters in the prediction maps
(Figures 1-4) equate to 0-30% variance
from ideal climate (black squares) to 3050% variance from ideal climate (open
circles) based on the ideal native and
naturalised climate mean. The black
squares represent those areas most at risk
of the analysed species establishing and
becoming problematic.
The naturalised range in Western
Australia (WA Herbarium 1998) was
included in each analysis to increase the
efficacy of the predictions. In many cases
a species can survive climatic conditions
overseas outside those it inhabits in its
native range, and a subsequent CLIMATE analysis may predict a wider
coverage than if the native range, alone,
were used. This ability to adapt to or
tolerate a range of climates is a common
characteristic of many weed species.
RESULTS
All four species analysed by CLIMATE showed good climate matches for
significant areas of California, from
Sonoma County south to San Diego
County. There were also a few locations
further north in Washington state where
populations of these species may establish,
although the cooler winters may limit
their spread and impact.
Bridal creeper is found along the
south coast of South Africa and northeast
through the Drakensberg into the
Transvaal (Kleinjan and Edwards 1999). It
was introduced to Australia in the mid1800s and earned its common name
through its widespread use in bridal
bouquets and floral arrangements.
Populations increased dramatically in the
late 20th century to the point where it
was named as a Weed Of National
Significance (WONS) in 1997 (Anon
2001). Bridal creeper occurs from
Dongara to Esperance in Western
Australia, as well as other areas across
southern Australia, and has been recorded
as naturalising in California near San
Diego, Los Angeles and San Francisco
(CalFlora 2002). The CLIMATE prediction (Figure 1) shows that large areas of
the Sacramento and San Joaquin Valleys
around Los Angeles, San Louis Obispo
and San Diego are climatically suitable for
establishment of bridal creeper.
In South Africa, taylorina occurs along
the coast from the Western Cape province
inland to Lesotho and north to the
Transvaal and is commonly found around
wetlands or soaks (Palgrave 1996).
Introduced to Western Australia as a
source of honey, taylorina has naturalised
extensively along the wetter south coastal
fringes from Albany and Denmark to
Margaret River and moist areas around
Perth.
Fig. 1
bridal creeper
SF
SD
Fig. 2
taylorina
SF
SD
Fig. 3
watsonia
(large arrow indicates
Sonoma and
Mendocino counties)
SF
SD
Fig. 4
arum lily
SF
Taylorina is not yet known to be
naturalised in California; however, plants
are available from at least once source in
San Francisco (Potrero Gardens 2002).
The CLIMATE prediction (Figure 2)
shows large areas of the Sacramento
Valley, Los Angeles and San Diego to be
climatically suitable for its establishment.
Watsonia is distributed along the
southwest Capes of southern Africa
(Goldblatt 1989) and was common in
cultivation in Australia prior to being
recognised as a ‘garden thug’ (Randall
2001).
Watsonia has naturalised through
much of the southwest of Western
Australia, as well as other areas across
southern Australia. Already well
naturalised in Mendocino and Sonoma
counties in California (CalFlora 2002)
watsonia is recognised as an invasive
species in the County of Mendocino town
planning regulations (County of
Mendocino 2002). The CLIMATE
prediction (Figure 3) shows large areas of
the San Joaquin Valley and around San
Diego and Los Angeles to he climatically
suitable for establishment.
Arum lily, also known as calla lily, is a
widely used ornamental around the world.
Its distribution in South Africa stretches
along the coast from the Western Cape
province, inland to Lesotho and north to
the Transvaal (Scott 1997). It is extremely
invasive in Western Australian wetlands
and irrigated pastures, particularly in the
Busselton-Margaret River area, and is also
naturalised in other southern States of
Australia. Arum lily has already been
noted naturalising around old homesteads
and seeps in Sonoma, Monterey and
Santa Clara counties (CalFlora 2002 and
Randall pers. comm. 2002). The CLIMATE prediction (Figure 4) shows that
large areas of the Sacramento and San
Joaquin Valleys, Los Angeles, San Louis
Obispo and San Diego are climatically
suitable for establishment.
DISCUSSION
SD
Many countries are looking at risk
assessment to identify and prioritise weed
threats for a range of reasons, including:
increased knowledge about the threat
of invasive plants to natural ecosystems;
knowledge of the ‘sleeper weed’
concept (i.e. the long lag phase between
introduction and impact);
trends towards an holistic biosecurity
approach rather than just quarantine for
agriculture;
the adoption of quarantine policies
that are based on formalised weed risk
assessment rather than simple prohibited
species lists; and
increased pressure from communities
expecting more from quarantine systems.
Some of these assessment processes are
time consuming and costly, and it is often
difficult to obtain data on particular
species.
Many scientists consider that many
parts of the world are entering an
‘homogocene’ era, or a ‘McDonaldisation’ of the world’s species.
That is, the replacement of regional
diversity by homogenous ecosystems,
characterised by cohorts of invasive
species that are the same worldwide. The
Mediterranean climate regions are no
exception and, because of their mild
climate and high human populations, are
likely to be the worst affected regions.
There is no shortage of examples of
Mediterranean species that have made an
impact around the world, including the
ubiquitous charlock (Sinapis arvensis L.),
which is found on every continent and is
a weed of crops in over 50 countries
(Holm et al. 1997) and common privet
(Ligustrum vulgare L.) which was a
favoured garden plant for centuries and is
now a major environmental weed on
several continents.
The Mediterranean climate is
characterised by having cool, wet winters
and warm to hot, dry summers. Regions
sharing this climate are the southwest of
Western Australia, parts of South Australia, southwestern California, southwestern
Africa, parts of Chile and the Mediterranean basin itself.
Examples of Australian native species
with demonstrated weedy behaviour in
Australia that clearly indicate potential
invasiveness in similar climates overseas,
are bluebell creeper and Victorian tea tree.
Bluebell creeper, a popular garden
plant native to southwest Western
Australia, has become an environmental
weed in southeastern Australia, creating
dense clumps that grow over existing
CalEPPC News
Spring 2003
5
downunder…
…continued from preivous page
native vegetation (Blood 2001). It is
present from Sonoma County to San
Diego County (Hickman 1993) in
California, but is not yet known to have
established in South Africa.
Victorian tea tree, a native of southeastern Australia, was used as an ornamental, coastal dune stabiliser and
windbreak (Blood 2001). After being
introduced to Western Australia, it
quickly spread into coastal heath and
woodlands in the lower southwest,
creating dense thickets. It is a declared
noxious weed in South Africa (Henderson
2001) and is also present in California
(CalFlora 2002).
Climate matching programs such as
CLIMATE or CLIMEX (Sutherst and
Maywald 1985) are useful tools for
predicting where such species may
establish, but are not essential when
generalising for major climatic types.
Because of their demonstrated weediness
in Australia, both Australian species
mentioned should be considered to have
significant potential to establish in other
Mediterranean climates.
It is worth noting that predictions for
three of the four species analysed show a
small area near Aberdeen in Washington
state (Figures 2-4) to be climatically
suited to allow growth. This is a reminder
that this type of analysis can only indicate
the gross areas of climatic suitability,
whereas many smaller microclimates with
their potentially unique vegetation might
not be indicated as suitable.
The documentation of known invasive
plant species within identified climate
types can be a fast and effective means to
identify potential new weeds in regions
with the same climate type.
REFERENCES
Anon. (200 I ). Bridal creeper (Asparagus asparagoides) Strategic Plan. National Weeds strategy
Executive Committee, Launceston. URL: www.
weeds.org.au/
Blood, K. (200 I). ‘Environmental weeds: A field
guide for SE Australia’. (C.H. Jerram and
Associates, Melbourne).
CalFlora: (2002). Information on California plants for
education, research and conservation. Berkeley,
California: The CalFlora Database. URL:
www.calflora.org/ (Accessed: March-April 2002)
County of Mendocino (2002). Gualala Town Plan
Chapter 6 -Appendices, B. Landscape Species
Lists. Invasive species: Not recommended for use
in landscaping plans. (March 2002) URL:
www.co.mendocino.ca.uslplanning/GTP/
gtpchap6.pdf
Goldblatt, P. ( 1989). ‘The genus Watsonia’. (National
Botanic Gardens, South Africa).
Henderson, L. (2001 ). Alien weeds and invasive
plants. Plant Protection Research Institute and
Agricultural Research Council, South Africa.
Hickman, J.C. (Ed.) (1993). ‘The Jepson manual.
Higher plants of California. 5th edition’. (University ofCalifornia Press California, USA).
Holm, L.G., Doll, J., Holm: E.,’ Pancho, J. V. and
Herberger, J.P. ( 1997). ‘World weeds. Natural
Arum lily in a woodland. Photo by John Randall, taken in Australia’s Leeuwin
Naturaliste National Park. The majority of trees in the oversory are Agonis
flexuosa, commonly known as peppermint or willow myrtle (Myrtaceae).
6
CalEPPC News
Spring 2003
histories and distribution’. (John Wiley and Sons
New York, USA).
Hussey, B.M,J., Keighery, G., Cousens, R.D., Dodd,
J. and Lloyd, S.G. ( 1997). ‘Western weeds, a
guide to the weeds of Western Australia’. (The
Plant Protection Society ofWA. Inc.)
Kleinjan, C.A. and Edwards, P.B. ( 1999). A
reappraisal of the identification and distribution
of Asparagus asparagoides in southern Africa. S.
African J. Bot. 65, 23-31.
Nix, N.H. ( 1986). A biogeographic analysis of
Australian elapid snakes. In’ Atlas of Australian
elapid snakes’, ed. R. Longmore, pp. 4-15.
(Bureau of Flora and Fauna, Canberra).
Palgrave, K.C. (1996). ‘Trees of Southern Africa’.
(Struik Publishers, Cape Town, South Africa).
Potrero Gardens (2002). Rare and unusua/ p/ants,
San Francisco (Accessed: March 2002). URL:
www.potrerogardens.com/autumn2001.htm
Randall, J.M. (2002). Personal cornrnunication. The
Nature Conservancy, Wildland Invasive Species
Team, California.
Randall, R.P. (2001). Garden thugs, a national list of
invasive and potentially invasive garden plants.
Plant Protection Quarterlv 16(4),138-171.
Scott, J.K. ( 1997). The distribution of arum lily and
its invasive potential. Proceedings of a workshop
on arum lily (Zantedeschia aethiopica) eds J.K.
Scott, and B.J. Wykes, 7 August 1997, Garden
Island, Western Australia. CRC for Weed
Management Systems, Adelaide, pp. 10-16.
Sutherst, R. W. and Maywald, G.F. ( 1985). A
computerized system for matching climates in
ecology. Agriculture, Ecosystems and Environment 13, 281-99.
Western Australian Herbarium ( 1998). FloraBaseInformation on the Western Australian flora.
(Accessed March-April, 2002). Department of
Conservation and Land Management. URL:
www. calm. wa.gov.aulscience/florabase.html.
The California Weed Science Society is
publishing a comprehensive identification
manual for aquatic and riparian weeds
west of the Rocky Mountains, with 560
color photos of 170 species of submerged,
floating leaf, and emergent aquatic weeds.
$5 discount for pre-publication orders!
Species Focus
Oxalis pes-caprae
By Jake Sigg
If one needs an illustration of the
function of natural controls on an
organism, they need look no further than
yellow oxalis (aka sour grass or Cape
sorrel, Oxalis pes-caprae), a scourge of the
California coast. It is a rare and endangered plant in its home range of South
Africa, where native fowl eat the foliage, a
© Br. Alfred Brousseau, Saint Mary’s College
mammal digs the bulbs, and parasites
infest bulbs. Freed from these energysuckers in California, its spread near the
coast is untrammeled.
The purpose of this article is (a) to
elicit help in determining how yellow
oxalis disperses, (b) to heighten awareness
of its surreptitious spread, and (c) to
suggest removal techniques and potential
problems with those techniques.
People are incredulous when learning
that viable seed from this plant has never
been reported in California. After
absorbing this information, their exasperated question follows: but HOW does it
get around? Oxalis’ abundant production
of bulb offsets and lateral runners partially
accounts for it but doesn’t fully explain its
alarming spread—how it travels so fast,
how it gets across the road, or one
hundred yards up the hill, or into a
second-floor flowerbox. Contaminated
soil may account for some occurrences
like the window-box, but that can’t
explain all the populations, especially in
wildlands.
The latest version of the CalEPPC
weed lists published in 1999 dodged the
question of how to rate yellow oxalis,
treating it as “needing more information.”
Up to then it had been considered a weed
of disturbed areas (a relative term—is
there any part of low-elevation California
that is not disturbed?). At this time oxalis
began rising on my personal worry list
and in the last three years I have become
panic-stricken as I see it proliferating
across landscapes. In heavy soils it
multiplies rapidly; in sand it explodes. In
a remnant native plant community
occupying a stabilized sand dune near my
house in western San Francisco, I
watched a small semi-circular infestation
with an approximate radius of twenty feet
spread seemingly exponentially in
approximately fifteen years to dominate
the whole ten-acre natural area, which is
now on its way to becoming a monoculture. I wasn’t watching its progress that
closely because I was too busy with other
concerns, but it surely did not spread
entirely by lateral runners. It must have
leap-frogged, but lacking time-lapse
photos, that will never be known. Now it
may not be possible to save the site’s
biological community.
I don’t know how or when it came to
California. Bailey’s 1930 The Standard
Cyclopedia of Horticulture listed it (as O.
cernua), so it was probably in the horticultural trade then. It is not listed in the
wild in the 1925 Jepson Manual. The
first mention of it as a weed known to me
was the 1951 Robbins, Bellue, and Ball
Weeds of California as O. cernua. They
reported it in orchards in the San
Francisco Bay Area and southern California. It may have been more widespread
than that, and it may have been in
cultivated sites before 1925. It has been
in the Mediterranean area since the 18th
century and it doesn’t produce seed there
either.
It certainly does like disturbance. (On
an amusing side note, a weed brochure
produced in the Bay Area recommended
getting rid of oxalis by rototilling, a surefire way of quadrupling its numbers
overnight! Please, please—don’t throw me
in that briar patch!) However, it no longer
requires active soil disturbance to
establish, and it is an increasingly
aggressive invader of native plant communities. Once established in a grassland,
dune, or even shrubland, its advance is
inexorable and without human intervention the outcome is inevitable. Although
it is active only during the brief rainy
season, when days are short and the sun is
low in the sky, populations nevertheless
rapidly expand, displacing plants that are
photosynthetically-active year-round.
Free of the need to produce extra energy
to support wildlife (nothing eats it), the
robust photosynthetic engine pumps out
enormous quantities of energy to pro-
from Robbins, Bellue, and Ball,Weeds of California, 1951, p272
duce—in about February or early
March—prodigious bulb offsets and
lateral runners to invade surrounding
areas and to muscle out even plants much
larger than it.
A lateral runner travels several inches
at a time; it is a peculiar fat, translucent
organ resembling an icicle, with emergent
slender, white, one-inch shoots at the tip
(see illustration next page). It inserts itself
continued next page…
CalEPPC News
Spring 2003
7
continued from previous page…
into the middle of an already crowded
clump of healthy natives, even into the
tight center of a vigorous bunchgrass or
rush, where it steadily burgeons, capturing space and light. Its roots compete
with the bunchgrass and even with native
shrubs such as coffeeberry or coyote bush.
Whether this direct competition can
weaken or eventually kill a shrub is not
established, but it is certain that it will
prevent a new generation of that or any
other plant at the site.
Thus, long-term prognosis is for a
monoculture of oxalis. No matter which
community is invaded, year-by-year the
oxalis becomes stronger and the other
plants become weaker. It even
outcompetes many aggressive weeds,
although it meets a worthy rival in the
same habitats preferred by its fellow
South African, Ehrharta erecta (see
CalEPPC News Summer/Fall 1996). It
will be interesting to see which of these
two bullies predominates on a given site;
ehrharta is the only plant I know that can
prevent oxalis from becoming a monoculture. (I am excepting another South
African, Cape ivy (Delairea odorata),
which in a favorable moist or shady site
will smother both oxalis and ehrharta.)
Eradication is difficult and timeconsuming because of that bulb. Removing a small infestation in a discrete area is
a feasible project. I was able to manually
rid it from my garden, which contained
many hundreds of oxalis plants, by
persisting in removal of the above-bulb
parts for four or five years. Repeated
timely removal of top-growth will deprive
the bulb of its stored energy. Optimum
time for this is winter or early spring just
before it starts producing offsets. Placing
fingers at soil level beneath the crown and
pulling gently but steadily (two hands
better) will frequently get the whole
taproot, especially when growing in sand.
The bulb will probably remain and still
have some stored energy to produce more
top-growth. A repetition of the preceding
operation during the same season will
either kill the plant or draw down its
energy so severely that one more pull
usually effects kill, providing it is welltimed and does not allow time for the
8 CalEPPC News
Spring 2003
bulb to recharge its energy. There is need
for monitoring for an additional two years
to make certain, as I have sometimes
found a single small leaf hiding among
other plants, slowly building up its bulb’s
strength for a comeback.
For large tracts spraying may be the
only option, although a judgment call
may arise if the oxalis is so intermixed
with the natives that killing it may entail
killing the natives. Some people reason
that they are going to lose the community
anyway, and eradicating the weed will
allow them to re-establish the natives. I
don’t know of definitive information on
the effectiveness of herbicides on oxalis
bulbs. Anecdotal information I received
says that 2% glyphosate is effective
providing you have a good surfactant,
since oxalis leaves tend to shed water. I
have not verified this information. A
further consideration is if the infestation
is in grasslands with few or no native
dicots present, triclopyr may be a better
choice, as it is designed to kill dicots but
not monocots.
I hope this article will elicit interest in
this pernicious weed and perhaps generate
a satisfactory explanation for its spread. I
borrowed an idea from scientist Joe
Balciunas, who offered a $100 reward for
anyone finding fertile seed of Cape ivy in
California for his biocontrol research
project. It worked for Cape ivy—viable
seed was found and Joe is $100 poorer. I
decided to make an identical offer to
anyone who produced viable seed or a
verifiable seedling of yellow oxalis, and I
published the offer in a recent issue of the
CNPS Yerba Buena Chapter newsletter.
Greatly to my surprise, botanist Lee Ellis
provided me color photocopies of
seedlings with cotyledon leaves from her
East Bay garden. This is very important
information and I encouraged her to
deposit herbarium specimens in the
Jepson Herbarium and with CDFA.
However, I do not think this answers
the question about the plant’s means of
dispersal, as I have checked innumerable
populations without finding viable seed or
young plants with cotyledon leaves. Until
proven otherwise, I will assume that seed
production is an uncommon occurrence,
and this accords with the information in
the Jepson Manual. If it is not uncommon, that would be vitally important
information. So the mystery is still there.
As Lee graciously declined the reward, I
will re-offer the $100 to the first party
producing proof.
Jake Sigg is Invasives Chair for the California Native Plant Society. He can be reached
at
Mom’s tips
My daughter shared her formula for
oxalis removal with me. Weed by hand
early in the season and often. The plant
puts out tiny nutlets near the crown as
the weather warms, in addition to the
flowers, and the idea is to get it out of
the ground before the nutlets and/or
flowers (and the next generation) have a
chance to form.
I have pulled all the plants in an area
only to go back a few days later to find
new ones. However, the new plants
appear to be smaller each time I return.
In some areas it’s stopped coming back.
She also suggested Roundup, but
that did not work for me, I think
because it is too cool here in the
Russian River watershed. The instructions say it needs to be 60 degrees to
work, and by the time it’s that warm the
nutlets and flowers will have formed.
One thing I find interesting is the
plant’s structure. It has a long root that
forms a 1″ nut about ten inches below
ground. Later in the season when I sift
through the soil I find these nuts below
the surface, sometimes attached to a
swollen white root like matter. That,
plus the scattered nutlets that spread
out when the plant is disturbed—no
wonder oxalis is so difficult to eradicate!
Victoria Wikle
Oxalis invades north coast dunes
Andrea Pickart of the Humboldt Bay National Wildlife Refuge in
northern California reports that O. pes-caprae has within the past two
years started to spread explosively into native dune habitats. It is now
encroaching upon endangered plant areas maintained by the Bureau of
Land Management and by the City of Eureka. She also reports that O.
pes-caprae is extremely aggressive, and that it the only plant that has
been observed surviving and coexisting with iceplant (Carpobrotus
edulis), another prolific invasive exotic species of coastal dune habitats.
Pickart adds that O. pes-caprae often forms dense mats in any area with
open space, and that is very successful at competing with and excluding
native plants. Even when it does not exclude natives, it has detrimental
impacts in open unvegetated areas, as it causes soil enrichment and
stabilization of semi-stable areas, altering ecosystem nutrient cycling.
[Info from The Nature Conservancy’s Wildland Invasive Species Team’s
website. Visit http://tncweeds.ucdavis.edu/alert/alrtoxal.html for more
information on oxalis.]
Sometimes we change our minds. A Boy Scout planting
pampas grass for the Soil Conservation Service in Los Angeles
County, 1953. [From a California Resource Conservation
Fund card. Thanks to Carla Koop for submitting the photo.]
New and Contributing Members
Thank you for your prompt renewals. We aplogize if we forgot you or got your information wrong! Please let us know by emailing
Sustaining Members:
Doug Allshouse (Friends of San Bruno Mountain, Daly City) · Greg
Archbald (Santa Barbara) · Gladys Baird (Encinitas) · Carolyn Johnson
& Rick Theis (Sebastapol) · Fred Kramer (San Diego) · William McCoy
(Berkeley) · Connie Rutherford (Ventura)
Contributing Members:
Martha Blane (Martha Blane & Associates, San Marcos) · Marian
Chambers (Central Sierra Partnership Against Weeds, Sonora) · Sarah
Chaney (Channel Islands National Park, Ventura) · Darlene Chirman
(Chirman Biological Consulting, Santa Barbara) · Tom Dodson (Tom
Dodson & Associates, San Bernardino) · Doug Elliott (US Forest
Service, Miwuk Village) · Lawrence Janeway (Chico) · Jo Kitz
(Mountains Restoration Trust, Woodland Hills) · Ralph Kraetsch
(Walnut Creek Open Space Foundation, Walnut Creek) · Jennifer
Langford (Jenesis Ecological Services, Avila Beach) · Mark Langner
(Bridgeport) · Susan Cochrane Levitsky (Cameron Park) · Tamia Marg
(Claremont Canyon Conservancy, Berkeley) · T. Charles Moore
(Sunnyvale) · Mike Peters (Fallbrook Land Conservancy, Fallbrook) ·
Susan Schwartz (Friends of Five Creeks, Berkeley) · Peter Slattery (Moss
Landing Marine Lab, Salinas) · Stephen Underwood (California State
Parks, McKinleyville) · · Clarence Weinmann (Berkeley) · Dolores
Welty (Encinitas) · Linda Willis (Soquel)
New Members:
Clay Courtwright (Stone Lakes National Wildlife Refuge, Elk Grove) ·
Mark Frey (Presidio Trust, San Francisco) · Yvette Redler (USDA APHIS
PPQ, Sacramento) · Jim Sharp (Berkeley) · Christopher Thayer (Sycamore
Associates, Walnut Creek) · Marilyn Walter (Portola Valley Ranch Landscape Committee, Portola Valley)
Gift Memberships:
Rosemary Gunn (Walnut Creek; gift from Mark Renz) · Adeline Gunnerson
(Walnut Creek; gift from Mark Renz) · Diane Nygaard (Preserve Calavera,
Carlsbad; gift from Ynez Yoder) · Mr. & Mrs. Doug Whiting (Carlsbad; gift
from Ynez Yoder) · Mr. & Mrs. Thomas Lyon (Oceanside; gift from Ynez
Yoder) · Bob Isaackson (Allan Hancock College, Lompoc; gift from Charles
Blair) · Nathan Hulse-Stephens (Davis; from Geri Hulse-Stephens)
Family Members:
Margaret Graham & Walter Earle (Mostly Natives Nursery, Tomales Bay) ·
Wilma & William Follette (Sausalito) · Franklin & Jean Olmstead (Foothills
Park, Palo Alto) · Don Stiver (CNPS, El Cerrito) · Michael & Jerre White
(Conservation Biology Institute, Encinitas)
Institutional Renewals:
Thomas Reid Associates (Palo Alto) · Jesse and Jason Giessow (Dendra, Inc.,
Encinitas) · Buford Crites (City of Palm Desert) · Ron Unger (EDAW,
Sacramento) · Cache Creek Conservancy (Woodland) · Mike Biscieglia
(DeAngelo Brothers, Inc., Chino) · Jean Ferreira (Elkhorn Native Plant
Nursery, Moss Landing) · Patricia Oliver (Ventura County Resource
Conservation District, Somis) · John Anderson (Hedgerow Farms, Winters) ·
David Gilpin (Pacific Coast Seed, Livermore) · Huntington Library (San
Marino) · Dave Moore (San Mateo County Parks, Redwood City) · City of
San Diego Park Rangers · California State Parks, Santa Cruz District ·
Helen Crocker Russell Library, Strybing Arboretum (San Francisco) · Small
Wilderness Area Preservation, Inc. (Los Osos) · Sue Gardner (Golden Gate
National Parks Association, San Francisco) · Steven Ash/IPM-PCA
Associates (San Rafael) · David Sands (Go Native Nursery, LLC, Montara) ·
Sue Weis (Inyo National Forest, Bishop)
CalEPPC News
Spring 2003
9
EDUCATION & OUTREACH
Inquiry in action: Using invasive
plants for teacher training
[CalEPPC awarded a mini-grant to the K12 Alliance in 2002.]
CalEPPC made a significant contribution to the training of California science
teachers this past summer. Using invasive
plant models and issues to learn about life
science concepts, twenty teachers, grades
5-12, became field researchers conducting
experiments and collecting and recording
data over a two-week period.
The K-12 Alliance is a school science
reform project in California. Teachers
participate in a two-week institute in the
summer, featuring science inquiry and
content sessions, and have follow-up
workshops during the school year. The K12 Alliance convenes institutes in
Sacramento, San Diego and the LA/
RIMS area (Los Angeles, Riverside, Inyo,
Mono, San Bernardino).
The LA/RIMS summer institute was
held at Diamond Ranch High School in
Diamond Bar, California, July 28 through
August 9. The teaching cadre consisted of
three teachers: Lorrae Fuentes, Director
of Education at Rancho Santa Ana
Botanic Garden; Keith Thompson,
Science Curriculum Coordinator and
former high school science teacher,
Fontana Unified School District; and Ian
Signer, Environmental Educator and
Curriculum Specialist at the California
Institute for Biodiversity. We planned
CalEPPC News
FANCY CARWASH
Portable Agricultural Soil Wash
By Lorrae Fuentes
10
Readings &
R e s o u rc e s
Spring 2003
lessons and activities throughout the
winter and spring, and decided early to
teach biology concepts around the central
theme of invasive species of plants.
We also wanted to provide resources
for teachers to get their students involved
in “action field projects” like weed
mapping, weed removal and habitat
restoration. Towards this end, we planned
a one-day field trip to Catalina Island as
part of the two-week institute. There are
extensive threats to native plant species by
invasives on the island, but the Catalina
Island Conservancy has an aggressive
research and restoration program. They
also have a comprehensive educational
outreach program.
CalEPPC, CNPS, and the Center for
Invasive Plant Management all contributed curriculum and print resources as
well as funds for getting teachers to
Catalina for a day of exploration. Thanks
to these organizations, twenty teachers
and their hundreds of students are far
more aware of invasive plants, and have
more understanding of the impacts on the
native plant communities of California.
Contact Lorrae at
An outfit from Platina has developed a
vehicle washing unit that can be leased to
clean fire-fighting vehicles on site. Wash
water can be drained on site or contained,
and pads absorb petroleum. Six spray
nozzles rinse vehicles’ undersides, and two
pressure washers allow you to wash
wheels, etc. Service includes a 3,000gallon water tender and two operators.
Info: Eddie Pokorny at 530/628-5669.
TEACHING BIODIVERSITY
Cal Alive!
California Institute for Biodiversity
Cal Alive! is an interactive CD-ROM set
covering California’s biological diversity
for grades 4-8. Experiments, stories,
games, fly-bys, and virtual field trips bring
the state’s 53 different habitats to the
classroom, promoting interactive learning
about the state’s climate, geology, ecology
and heritage. Classroom guides and
teacher resource guides are included.
SPECIAL SECTION
Journal of Conservation Biology
The February issue of Conservation
Biology has a six-paper special section on
the “Population Biology of Invasive
Species” from authors including CalEPPC
member Ingrid Parker of UC Santa Cruz.
Wal-Mart stops
selling pampas
grass in California
Letter from Carolyn Martus
[CalEPPC member Carolyn Martus of
Carlsbad got frustrated when she saw
pampas grass for sale at WalMart, and wrote
them an email. It was forwarded to
WalMart’s west coast buyer, who decided to
take pampas grass off the master list of
plants available to stores! Carolyn also
convinced an REI store to remove pampas
grass from their landscaping. She has now
turned her attention to other big box outlets
where the plant is sold.]
I’ve received lots of kudos and
congratulations for getting WalMart to
take pampas grass off their shelves, but I
have to admit that it was pretty easy and
uncontroversial. It took all of about 15
minutes to pull up their website, go to
their customer service section and
compose a few sentences. I wrote them a
very short email, one paragraph long, and
included a link to Carrie Schneider’s
proposal to the City of San Diego to ban
pampas grass.
Briefly, I told WalMart that pampas
grass is wreaking havoc in our open spaces
and if they want to help the environment,
they need to take it off their shelves. My
email was concise and positive. I congratulated them for giving back to the
community and stressed how we needed
to work together to help the environment. I believe most people and businesses will do the right thing once they
know they are causing harm to a community or environment.
Until CalEPPC can convince CDFA
to list Cortaderia selloana as a noxious
weed, it will be up to individuals to
educate others. Make it your New Year’s
resolution to talk to one neighbor or local
business about pampas grass, and get some
educational materials to help your case.
For an excellent brochure to use when
talking to people about pampas grass, visit
at c_martus@yahoo.com. To express support
for Linda Prendergast’s decision to remove
pampas grass from WalMart shelves, write
her at 3233 Grand Ave., Suite N-411,
Chino Hills, CA 91709-1489.
The WILDLAND WEED CALENDAR
National Invasive Weed Awareness Week
February 24-28
Washington, DC
Sponsored by the California Sea Grant
College System and The MIT Sea Grant
College Program.
4th annual gathering of weed managers
to participate in visible public activities
and to lobby their representatives.
2003 Western Society of Weed Science
Annual Meeting
A week to plan local weed tours, newspaper articles and other outreach events. For
ideas from WMAs that sponsored events
last year, contact Nancy Brownfield at
at
March 11-13, 2003
Koloa, HI
California Weed Awareness Week
July 6-12
Third International Conference on
Marine Bioinvasions
Save the date!
March 16-19, 2003
Scripps Institution of Oceanography,
La Jolla, CA
October 2-4
North Tahoe Conference Center
CalEPPC Symposium 2003
Quotable:
The International Union for the
“Conservation
of Nature estimates that since 1600, 109
With international trade at unpre“cedeted
volumes, the worldwide reshuffling of organisms
species of mammals, birds, reptiles, amphibians, fishes,
invertebrates, and vascular plants have become extinct in
what is now the continental United States… at least
4,500 nonindigenous species have established free-living
populations in the United States over the past few
hundred years… On balance, this part of the world has
seen an increase in biological diversity.
is now a major driver of global change. We live in a time
the ecologist Gordon Orians dubbed “The Homogocene”
to describe how once unique places have come to resemble each other—with massive environmental and
economic impacts.
”
Allan Fitzsimmons, newly appointed wildlands fuel coordinator for the Department of the Interior, from a Fall 2000
issue of Markets and Morality as reported in Sierra, Jan/Feb
2003).
”
Phyllis Windle, Union of Concerned Scientists,”Connecting
the dots: Bringing the invasive species issue into focus,” Fall
2002, Catalyst (semiannual magazine of UCS) 1(2):14.
CalEPPC News
Spring 2003
11
CalEPPC Membership Form
We’re working to protect California’s wildlands from invasive plants—join us!
CalEPPC’s effectiveness comes from a strong membership, including scientists, land managers, policy makers, and concerned citizens.
Please photocopy the form below, complete, and mail with your payment. Additional donations are always welcome to support our
projects; we are a 501(c)3 nonprofit organization, and donations beyond regular membership rates are tax deductible.
Individual
Student/low income
$15
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$30
Family
$40
Contributing
$50
Sustaining
$100
Life
$1,000
Additional donations for:
Cape ivy bioconrols research
International Broom Initiative
Educational outreach and materials
Cal-EPPC News and operating costs
Institutional
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$500
Sustaining
$1,000
Name
Affiliation
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$
$
Please mail check (to “Cal-EPPC”) and this form to:
Cal-EPPC Membership
1442-A Walnut Street #462
Berkeley CA 94709
California
Exotic Pest Plant
Council
1442-A Walnut Street, #462
Berkeley, CA 94709
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