Plant Assessment Form

Gazania linearis

Synonyms: Gazania longiscapa DC

Common Names: gazania; treasure flower

Evaluated on: 6/27/11

List committee review date:

Re-evaluation date:

Evaluator(s)

Elizabeth Brusati
Cal-IPC
Cal-IPC, 1442-A Walnut St. #462, Berkeley, CA 94709
510-843-3902
edbrusati@cal-ipc.org
Joseph M. DiTomaso, Specialist in Cooperative Extension
Dept. of Plant Sciences, University of California-Davis
Mail Stop 4, One Shields Ave., Davis CA 95616
530-754-8715
jmditomaso@ucdavis.edu

No list committee members listed

General Comments

There is basically no published literature on this species. A Web of Science search brought up one conference paper and one patent for a horticultural cultivar, plus two more under the name Gazania longiscapa.

Table 2. Criteria, Section, and Overall Scores

Overall Score? Moderate
Alert Status? Alert
Documentation? 2 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes C Observational
Impact?
Four-part score CBUD Total Score
B
1.2 ?Impact on plant community B. Moderate Observational
1.3 ?Impact on higher trophic levels U. Unknown
1.4 ?Impact on genetic integrity D. None Reviewed Scientific Publication
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Observational
Invasiveness?
Total Points
13 Total Score B
2.2 ?Local rate of spread with no management B. Increases less rapidly Observational
2.3 ?Recent trend in total area infested within state B. Increasing less rapidly Observational
2.4 ?Innate reproductive potential
(see Worksheet A)
A. High Other Published Material
2.5 ?Potential for human-caused dispersal A. High Other Published Material
2.6 ? Potential for natural long-distance dispersal D. None Observational
2.7 ?Other regions invaded C. Already invaded Other Published Material
3.1 ?Ecological amplitude/Range
(see Worksheet C)
B. Moderate Observational
Distribution?
Total Score C
3.2 ?Distribution/Peak frequency
(see Worksheet C)
D. Very low Observational

Table 3. Documentation

Scores are explained in the "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands".

Section 1: Impact
Question 1.1 Impact on abiotic ecosystem processes? C Observational
Identify ecosystem processes impacted:

It forms a dense groundcover, preventing erosion on creek banks.


Sources of information:

Christina Danko, pers. comm.


Question 1.2 Impact on plant community composition,
structure, and interactions?
B Observational
Identify type of impact or alteration:

Outcompetes all native groundcover/herbaceous plantings. In riparian mitigation areas, we have seen this plant form a groundcover within one year, choking out seedlings from native riparian hydroseeded plantings. (Christina Danko, pers. comm.)
In McClaren Park in San Francisco, it has spread into remnant patches of native grassland, including Nassella pulchra, Danthonia californica, and Elymus glauca. Also affecting a locally endemic plant. (Jake Sigg, pers. comm.)


Sources of information:

Christina Danko, personal communication
Jake Sigg, San Francisco, personal communication, 2/3/10


Question 1.3 Impact on higher trophic levels? U
Identify type of impact or alteration:

Sources of information:

Jake Sigg, personal communication 2/3/10


Question 1.4 Impact on genetic integrity? D Reviewed Scientific Publication

None. No native Gazania congeners in California.


Sources of information:

Hickman, J. C. (ed.) 1993. The Jepson Manual, Higher Plants of California. University of California Press. Berkeley, CA enter text here


Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
B Observational
Describe role of disturbance:

Wherever it is planted nearby as a groundcover ornamental we see wind blown invasion into surrounding areas, usually into riparian mitigation areas that have been disturbed and are being restored (Christina Danko, pers. comm).
Spreading due to human disturbance in McClaren Park but the areas it is invading are remnant patches of fairly undisturbed native grassland (never tilled, etc.). (Jake Sigg, pers. comm.)


Sources of information:

Question 2.2 Local rate of spread with no management? B Observational
Describe rate of spread:

I am located in central California within the fog belt. Over the course of several years I have seen gazania expand on a neighboring property which is regularly mowed for vehicle parking. It crossed over onto adjacent BLM property, which is maintained as grassland, but the rate of spread seemed slow. However, this year a couple of people have commented to me that its range has expanded from last year and GPS data shows this to be true. Mostly troubling is one plant that was found about a mile from the orginal location (Sue Hubbard, pers. comm).
Seen spreading in riparian areas in Ventura (Christine Danko, pers. comm.)
Has spread quickly in McClaren Park, San Francisco. This is the only site where Jake has seen it but it spread rapidly from a planting in an adjacent parking lot. (Jake Sigg, pers. comm.)


Sources of information:

Emails from Sue Hubbard, Weed Crew Supervisor, Bureau of Land Management, Fort Ord (pers. )
Christina Danko, pers. comm.
Jake Sigg, pers. comm.


Question 2.3 Recent trend in total area infested within state? B Observational
Describe trend:

Spreading? Has been seen becoming invasive fairly recently in several areas of California.


Sources of information:

Question 2.4 Innate reproductive potential? A Other Published Material
Describe key reproductive characteristics:

Perennial from stolons or rhizomes. Self-sowing. Difficult to remove because it develops a tap root.


Sources of information:

Question 2.5 Potential for human-caused dispersal? A Other Published Material
Identify dispersal mechanisms:

Sources of information:

Brenzel 2001


Question 2.6 Potential for natural long-distance dispersal? D Observational
Identify dispersal mechanisms:

Probably unlikely? But see comment from Sue Hubbard that one plant was found a mile from the rest of the infestation at Fort Ord. Jepson manual indicates that pappus is only slender scales, thus not capable of wind dispersal. May occasionally be dispersed by birds or water, but vast majority of seed likely fall to ground below parent plant.


Sources of information:

Sue Hubbard, personal observation
Joseph M. DiTomaso, personal observation
Jepson Manual


Question 2.7 Other regions invaded? C Other Published Material
Identify other regions:

Gazania is widespread and common in Victoria and naturalised in South Australia and Western Australia.
Native to South Africa. Also invasive in Australia. California is the only state listed where naturalized in US by USDA PLANTS database.
Listed as one of the "ten most serious invasive plants sold by nurseries in Australia" (Groves et al. 2005)


Sources of information:

http://www.weeds.org.au/cgi-bin/weedident.cgi?tpl=plant.tpl&ibra=all&card=E18
Groves et al. 2005
USDA NRCS 2011


Section 3: Distribution
Question 3.1 Ecological amplitude/Range? B Observational

Riparian areas in the Simi Valley, Moorpark, and Newbury Park/Thousand Oaks area, Ventura County. WeedWatch, of the Los Angeles and San Gabriel Rivers Watershed Council, finds that gazanias invade these environments: riparian/wetland, coastal, coastal sage, chaparral, grassland, desert. (Christina Danko, pers. comm)
Gazania linearis is a problem plant in McLaren Park in San Francisco. About 15 years ago I commented on a list of plants to be planted in a median strip on the road running through the park. At my request they removed all the known invasives. At that time I had not known gazania to be problematic. Within a couple of years I was suffering remorse, as it jumped a four-lane road and is spreading into the grasslands. (Jake Sigg, pers. comm.)
Specimens in the Consortium of California Herbaria database in coastal counties from the San Francisco Bay Area to San Diego, as well as Riverside County. Some are within urban areas, others seem to be along trails.


Sources of information:

Christina Danko, pers. com.
Jake Sigg, pers. comm.
LASGRWC, date unknown
CCH. 2011.


Question 3.2 Distribution/Peak frequency? D Observational
Describe distribution:

Probably a low frequency in any particular habitat type on a statewide level.


Sources of information:

Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less Unknown
Dense infestations produce >1,000 viable seed per square meter Yes
Populations of this species produce seeds every year. Unknown
Seed production sustained over 3 or more months within a population annually Yes
Seeds remain viable in soil for three or more years Unknown
Viable seed produced with both self-pollination and cross-pollination Unknown
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes Unknown
Fragments easily and fragments can become established elsewhere Unknown
Resprouts readily when cut, grazed, or burned Yes
Total points: 4
Total unknowns: 6
Total score: B?

Related traits:

Worksheet B - Arizona Ecological Types is not included here

Worksheet C - California Ecological Types

(sensu Holland 1986)
Major Ecological Types Minor Ecological Types Code?
Marine Systemsmarine systems
Freshwater and Estuarine lakes, ponds, reservoirs
Aquatic Systemsrivers, streams, canals
estuaries
Dunescoastal
desert
interior
Scrub and Chaparralcoastal bluff scrub
coastal scrub
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrub
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparral
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairieD, < 5%
valley and foothill grassland
Great Basin grassland
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swamp
Riparian and Bottomland habitatriparian forest
riparian woodlandD, < 5%
riparian scrub (incl.desert washes)
Woodlandcismontane woodland
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
North Coast coniferous forest
closed cone coniferous forest
lower montane coniferous forest
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth): B
Distribution (highest score): D

Infested Jepson Regions

Click here for a map of Jepson regions

  • Central West
  • Southwest