Plant Assessment Form

Anthoxanthum odoratum

Common Names: sweet vernal grass; vanilla grass

Evaluated on: 12/27/04

List committee review date:

Re-evaluation date:


Elizabeth Brusati, project manager
California Invasive Plant Council
1442A Walnut St. #462, Berkeley, CA 94709
Peter J. Warner; ecologist
California State Parks
P. O. Box 603, Little River, CA 95456
707-937-9172; 707-937-2278

List committee members

Carla Bossard
John Randall
Cynthia Roye
Jake Sigg
Peter Warner

General Comments

More quantitative data and observational evidence on the distribution and impacts of this common plant in California are needed to strengthen this assessment.

Table 2. Criteria, Section, and Overall Scores

Overall Score? Limited
Alert Status? No Alert
Documentation? 3 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes U. Unknown Reviewed Scientific Publication
Four-part score UBDD Total Score
1.2 ?Impact on plant community B. Moderate Reviewed Scientific Publication
1.3 ?Impact on higher trophic levels D. Negligible Observational
1.4 ?Impact on genetic integrity D. None Reviewed Scientific Publication
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Reviewed Scientific Publication
Total Points
12 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)
B. Moderate Other Published Material
2.5 ?Potential for human-caused dispersal B. Moderate Observational
2.6 ? Potential for natural long-distance dispersal C. Rare Other Published Material
2.7 ?Other regions invaded C. Already invaded Reviewed Scientific Publication
3.1 ?Ecological amplitude/Range
(see Worksheet C)
B. Moderate Other Published Material
Total Score B
3.2 ?Distribution/Peak frequency
(see Worksheet C)
B. Moderate 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? U Reviewed Scientific Publication
Identify ecosystem processes impacted:

no information

Sources of information:

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

Outcompetes other grasses (1). Live plants have allelopathic effect (2) but root material may improve growth of some other grasses (3). Develops dense surface root mat (1). Invades disturbed areas and prevents re-establishment of native species (4).
Not observed to completely displace either native or non-native plants, even as a dominant species in heavily invaded areas (5). Anthoxanthum shoots depressed germination of grass seed but tended to promote germination of legumes (2). Decomposing roots of Anthoxanthum increased growth of subsequent plants (of other species) (3). However, personal observations (5) suggest that this plant does not severely alter species composition, even in heavily infested coastal prairie.

Sources of information:

1. Pitcher D., and M. J. Russo. 1988. Element Stewardship Abstract for Anthoxanthus odoratum. The Nature Conservancy, Washington, D.C.
2. Scott D. 1975. Allelopathic interactions of resident tussock grassland species on germination of oversown seed. New Zealand Journal of Experimental Agriculture 3: 135-141.
3. Newbery D. McC. 1979. The effects of decomposing roots on the growth of grassland plants. Journal of Applied Ecology 16: 613-622.
4. U.S. Forest Service, Institute of Pacific Islands Forestry. Pacific Islands Ecosystems at Risk.
5. Warner, PJ. Personal observations. Marin, Sonoma, Mendocino Counties, 1996-2005. 707/937-2278;

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

Planted as a forage crop, so is probably palatable to livestock. Browsing of coastal prairie plants suggest that the plant is used by wild animals, perhaps rabbits, voles, mice, and deer (1). very casual observations and anecdotes suggest that this plant does not negatively affect native animal species, but is a palatable plant.

Sources of information:

1. Warner, PJ. Personal observations, Salt Pt. State Park (Sonoma Co.), and Mendocino Co. (various locations), 1996-2005. 707/937-2278;

Question 1.4 Impact on genetic integrity? D Reviewed Scientific Publication

none no native Anthoxanthum spp.

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:

Needs to germinate in disturbed areas (1). However, it does germinate and spread into marginally optimal habitats that lack regular disturbance, such as observed at forest edges in Mendocino County (2). Adult transplants in New Zealand could survive without disturbance, but seedlings could not germinate without it. Germination occurred near back-country huts and rivers (1). But, Anthoxanthum appears to germinate well in relatively undisturbed sites, perhaps where competition from other herbaceous perennials and annuals is minimal (2).

Sources of information:

1. Jesson, L., D. Kelly, and A. Sparrow. 2000. The importance of dispersal, disturbance, and competition for exotic plant invasions in Arthur's Pass National Park, New Zealand. New Zealand Journal of Botany 38(3): 451-468.enter text here
2. Warner, PJ. Personal observations. Marin, Sonoma, Mendocino Counties, 1996-2005. 707/937-2278;

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

Other than very limited observational evidence, no information. However, Anthoxanthum does spread into uninvaded areas at a relatively slow rate, based on observations with hand-pulling and subsequent reintroduction into those areas (some of which could be due to regeneration from rhizomes, and not from seeds only) (1). very much a guess based on limited personal observations.

Sources of information:

1. Warner, PJ. Personal observations. Marin, Sonoma, Mendocino Counties, 1996-2005. 707/937-2278;

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

Anthoxanthum has been well established in California for a very long time, perhaps over 100 years. Most suitable habitat appears to have been exploited, so the trend appears virtually stable (1). However, one observation suggests that upland, moist sites may have been invaded more recently (2), but is this based upon long-time observations, or other evidence, that it was not present until recently? Assessment based on history of establishment and land uses for grazing, along with observations (1).

Sources of information:

1. Warner, PJ. Personal observations. Marin, Sonoma, Mendocino Counties, 1996-2005. 707/937-2278;
2. Hayes, G. Personal communication to P. Warner, 2004.

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

Short-lived, perennial, outcrossing grass (1). Significant differences in morphological traits can develop as adaptations to soil conditions (1). Reproduces from seeds. Self-incompatible. In North Carolina, produced 58 - 1257 seeds/plant (2). Some seeds able to germinate after a year's dormancy (2). Other studies found that buried seeds were not viable after 10 months (2). Seeds have awns that allow them to move within the soil (2). Biology depends upon habitat of a particular population, with higher turnover rates and shorter life of individuals in ecologically marginal populationsn (2).

Sources of information:

1. Kiang Y.T. 1982. Local differentiation of Anthoxanthum odoratum L. populations on roadsides. American Midland Naturalist 107(2): 340-350
2. Pitcher and Russo 1988.

Question 2.5 Potential for human-caused dispersal? B Observational
Identify dispersal mechanisms:

Near-certain transport along roads (1,2), by mowing equipment, on hiker's shoes (2). I found no information on this, but the literature mentions it occurring along roadsides and in pastures, so presumably seeds could be transported on road equipment or other vehicles. The fact that it occurs near backcountry huts in New Zealand implies that it was transported by hikers (1). Very likely, this species is spread primarily through human impacts, such as mowing and hiking, and especially along roads and trails (2).

Sources of information:

1. Jesson et al. 2000.
2. Warner, PJ. Personal observations. Marin, Sonoma, Mendocino Counties, 1996-2005. 707/937-2278;

Question 2.6 Potential for natural long-distance dispersal? C Other Published Material
Identify dispersal mechanisms:

Seed dispersed by wind, water, and animals, but no information on the distance of dispersal. U.S. Forest Service, Institute of Pacific Islands Forestry. Pacific Islands Ecosystems at Risk.

Sources of information:

Question 2.7 Other regions invaded? C Reviewed Scientific Publication
Identify other regions:

Native to Eurasia. Has invaded New Zealand (1), Taiwan (2), Chile (open areas, dry soils, humid rock, seaside areas, etc. (3). In US, ranges from northern Florida to southern Canada along east coast, and west to Mississippi River. On west coast, occurs from northern California to Vancouver Island (4). Present on TNC preserves in Oregon, west of the Cascades to the coast (4). In Hawaii, naturalized in pastures, disturbed areas in wet forest, and subalpine shrubland (5). From the literature, Anthoxanthum has probably invaded most, if not all, suitable habitats here in California. However, more evidence of ecotypes invaded (especially upland sites away from the immediate coast) could alter this assessment.

Sources of information:

1. Jesson et al. 2000
2. Kuoh, C.-S., G.-I. Liao, and M-Y. Chen. 1999. Two new naturalized grasses in Taiwan. Taiwania 44(4): 514-519.
3. Baeza, C. M., T. F. Stuessy, and C. Marticorena. 2002. Notes on the Poaceae of the Robinson Crusoe (Juan Fernandez) Islands, Chile. Brittonia 54(3): 154-163.
4. Pitcher and Russo 1988
5. U.S. Forest Service, Institute of Pacific Islands Forestry, Pacific Islands Ecosystems at Risk

Section 3: Distribution
Question 3.1 Ecological amplitude/Range? B Other Published Material

Introduced to North America as meadow grass in 1700's and escaped from cultivation (1). Observational evidence suggests that this taxon is restricted to coastal areas, primarily north of the San Francisco Bay Area. Anthoxanthum is widespread in coastal prairie habitats, and also invades moist, open sites in closed cone pine and north coast coniferous forests (2). Assessment based on limited observations in 3 counties along northern California coast.

Sources of information:

1. Pitcher and Russo. 1988
2. Warner, PJ. Personal observations. Marin, Sonoma, Mendocino Counties, 1996-2005. 707/937-2278;

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

Anthoxanthum is virtually ubiquitous in coastal prairie habitat from the Russian River north through Mendocino County, and probably further north (1). Although not as common further south, it does invade upland grassland habitats and disturbed sites in the Santa Cruz Mountains (2). Assessment based on limited and undocumented observations - a cautious guess.

Sources of information:

1. Warner, PJ. Personal observations. Marin, Sonoma, Mendocino Counties, 1996-2005. 707/937-2278;
2. Hayes, G. Personal communication to P. Warner, 2004.

Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less Yes
Dense infestations produce >1,000 viable seed per square meter Yes
Populations of this species produce seeds every year. Yes
Seed production sustained over 3 or more months within a population annually No
Seeds remain viable in soil for three or more years No
Viable seed produced with both self-pollination and cross-pollination No
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes No
Fragments easily and fragments can become established elsewhere No
Resprouts readily when cut, grazed, or burned Yes
Total points: 5
Total unknowns: 0
Total score: B?

Related traits:

Seeds produced annually from most plants; responds vigorously to grazing, mowing, or burning.

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
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
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairieB, 20% - 50%
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 woodland
riparian scrub (incl.desert washes)
Woodlandcismontane woodland
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
North Coast coniferous forestC, 5% - 20%
closed cone coniferous forestC, 5% - 20%
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): B

Infested Jepson Regions

Click here for a map of Jepson regions

  • Cascade Range
  • Central West
  • Great Valley
  • Northwest
  • Sierra Nevada
  • Southwest