Plant Assessment Form

Asphodelus fistulosus

Synonyms: Asphodelus tenuifolius Cav.

Common Names: onion weed; asphodel; hollow stemmed asphodel; wild onion

Evaluated on: 8/9/04

List committee review date: 27/08/2004

Re-evaluation date:

Evaluator(s)

Jonathan C. Fox/ Research Associate
California Polytechnic State University, San Luis Obispo
591 Rosina Dr. Los Osos, CA 93402
(805) 528-7091
anyplacewild@kcbx.net

List commitee members

John Randall
Alison Stanton
Cynthia Roye
Jake Sigg
Joe DiTomaso
Peter Warner

General Comments

Origin - extends from Mediterranean region through Asia Minor to western Asia and northern India.

Table 2. Criteria, Section, and Overall Scores

Overall Score? Moderate
Alert Status? Alert
Documentation? 3 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes C Other Published Material
Impact?
Four-part score CBCD Total Score
B
1.2 ?Impact on plant community B. Moderate Other Published Material
1.3 ?Impact on higher trophic levels C. Minor Other Published Material
1.4 ?Impact on genetic integrity D. None Reviewed Scientific Publication
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Other Published Material
Invasiveness?
Total Points
17 Total Score A
2.2 ?Local rate of spread with no management A. Increases rapidly Other Published Material
2.3 ?Recent trend in total area infested within state A. Increasing rapidly Reviewed Scientific Publication
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 C. Rare Other Published Material
2.7 ?Other regions invaded B. Invades 1 or 2 ecological types Other Published Material
3.1 ?Ecological amplitude/Range
(see Worksheet C)
B. Moderate Other Published Material
Distribution?
Total Score C
3.2 ?Distribution/Peak frequency
(see Worksheet C)
D. Very low Reviewed Scientific Publication

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 Other Published Material
Identify ecosystem processes impacted:

In dense patches, lowered soil nitrogen prevents other plants establishing and competing with the weed (1).


Sources of information:

(2)Parsons W.T., Cuthbertson E.G. "Onion Weed," Noxious Weeds of Australia. Pgs. 90-92. Year unknown.


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

Displacement and increased grazing pressure on palatable grasses, herbs and shrubs (1). A. fistulosus is unpalatable and generally not eaten by livestock, native herbivores and feral animals(1). Onion weed grows so thickly it considerably reduces other vegetation, particularly grasses(2).


Sources of information:

(1)Turner J. The Impact of Onion weed dominance on biodiversity, total grazing pressure and pastoral enterprises in the Eastern Districts and North East Pastoral Soil Conservation Districts. 1999.
(2)Underwood, J.A., Mesa E. Asphodelus fistulosis, Onion weed Texas Infestation Status Report. 2001


Question 1.3 Impact on higher trophic levels? C Other Published Material
Identify type of impact or alteration:

A. fistulosis infestations may have a negative impact on native birds or insects that feed on or inhabit native grasses (1). see question 1.2.


Sources of information:

(1)Turner J. The Impact of Onion weed dominance on biodiversity, total grazing pressure and pastoral enterprises in the Eastern Districts and North East Pastoral Soil Conservation Districts. 1999.


Question 1.4 Impact on genetic integrity? D Reviewed Scientific Publication

No hybridization in literature. No other member of genus Asphodelus in California (1).


Sources of information:

Hickman, J.C.(e.d.)1993. Asphodelus. pp.1179-1180. The Jepson manual: vascular plants of California. University of California Press, Berkeley. 1400


Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
A Other Published Material
Describe role of disturbance:

Described in literature as "a weed of disturbed sites". It thrives wherever there is little competition from other plants (1). Beginning to move into grasslands and other wildland sites following burning (2).


Sources of information:

(1)Turner J. The Impact of Onion weed dominance on biodiversity, total grazing pressure and pastoral enterprises in the Eastern Districts and North East Pastoral Soil Conservation Districts. 1999.
(2)DiTomaso J., Healy E. Weeds of California and Other Western States. As yet unpublished.


Question 2.2 Local rate of spread with no management? A Other Published Material
Describe rate of spread:

Rapid rate of spread.


Sources of information:

(1)Underwood, J.A., Mesa E. Asphodelus fistulosis, Onion weed Texas Infestation Status Report. 2001
(2)Fox, J.C. 2004. Personal observations during 2000-2004 Centaurea solstitialis roadside surveys for SLO County Ag Department, CA. (805)528-7091, anyplacewild@kcbx.net


Question 2.3 Recent trend in total area infested within state? A Reviewed Scientific Publication
Describe trend:

Federally listed noxious weed. Current distribution: South and Central Coast, sothern San Joaquin Valley, to about 800 m, and possibly elsewhere. Expected to expand range (4).


Sources of information:

(1)Underwood, J.A., Mesa E. Asphodelus fistulosis, Onion weed Texas Infestation Status Report. 2001
(2)Parsons W.T., Cuthbertson E.G. "Onion Weed," Noxious Weeds of Australia. Pgs. 90-92. Year unknown.
(3)Patterson, D.T. 1996. Temperature and Photoperiod Effects on Onionweed (Asphodelus fistulosus) and Its Potential Range in the United States. Weed Technology. 10(4):684-688.
(4)DiTomaso J., Healy E. Weeds of California and Other Western States. As yet unpublished.
(5)Turner J. The Impact of Onion weed dominance on biodiversity, total grazing pressure and pastoral enterprises in the Eastern Districts and North East Pastoral Soil Conservation Districts. 1999.


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

Reach reproductive maturity at 18 months (1). Plants produce an average of 2,325 seeds/plant/year, and mature plants may produce as many as 13,200 seeds (2). Annual to short-lived perennial (3). Flowers February-April, except along southern California coast where plants can flower much later (3). Seed remains viable in the soil for many years (1). Onion weed plants form no distinct bulb, and reproduce by seed (2).


Sources of information:

(1)Underwood, J.A., Mesa E. Asphodelus fistulosis, Onion weed Texas Infestation Status Report. 2001
(2)Turner J. The Impact of Onion weed dominance on biodiversity, total grazing pressure and pastoral enterprises in the Eastern Districts and North East Pastoral Soil Conservation Districts. 1999.
(3)DiTomaso J., Healy E. Weeds of California and Other Western States. As yet unpublished.


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

The main method of spread is by seeds which can be dispersed in many ways such as on vehicles, machinery(road works), clothing and farm produce (1).


Sources of information:

(1)Underwood, J.A., Mesa E. Asphodelus fistulosis, Onion weed Texas Infestation Status Report. 2001
(2)Fox, J.C. 2004. Personal observations during 2000-2004 Centaurea solstitialis roadside surveys for SLO County Ag Department, CA. (805)528-7091, anyplacewild@kcbx.net


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

Natural long distance dispersal of seeds can occur by animals, wool and by water in open channels (1).


Sources of information:

(1)Underwood, J.A., Mesa E. Asphodelus fistulosis, Onion weed Texas Infestation Status Report. 2001
(2)Turner J. The Impact of Onion weed dominance on biodiversity, total grazing pressure and pastoral enterprises in the Eastern Districts and North East Pastoral Soil Conservation Districts. 1999.
(3)Parsons W.T., Cuthbertson E.G. "Onion Weed," Noxious Weeds of Australia. Pgs. 90-92. Year unknown.


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

Western AU, coastal heath scrub similar to maritime chaparral or chaparral.


Sources of information:

(1)Parsons W.T., Cuthbertson E.G. "Onion Weed," Noxious Weeds of Australia. Pgs. 90-92. Year unknown.
(2)DiTomaso J., Healy E. Weeds of California and Other Western States. As yet unpublished.
(3) Observational John Randall, Peter Warner, Joe DiTomaso. 2004.


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

No date in literature of earliest introduction into CA. CDFA herbarium has vouchered specimen for San Luis Obispo County from 1957. Habitat described for CA includes: fields, pastures, roadsides, coastal dunes, orchard and agronomic crops, and other disturbed places, especially those with sparse vegetation. Beginning to move into grasslands and other wildland sites following burning (1).


Sources of information:

(1)DiTomaso J., Healy E. Weeds of California and Other Western States. As yet unpublished.


Question 3.2 Distribution/Peak frequency? D Reviewed Scientific Publication
Describe distribution:

Sources of information:

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 Yes
Seeds remain viable in soil for three or more years Yes
Viable seed produced with both self-pollination and cross-pollination Unknown
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 Unknown
Total points: 7
Total unknowns: 2
Total score: A?

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
DunescoastalD, < 5%
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 grasslandD, < 5%
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 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
  • Great Valley
  • Southwest