Plant Assessment Form

More Pistia stratoites resources

Pistia stratoites

Synonyms: Apiospermum obcordatum, Pistia aegyptiaca, Pistia crispata, Pistia spathulata

Common Names: water lettuce, water cabbage, Nile cabbage, shellflower

Evaluated on: 3/31/2026

List committee review date: 31/05/2026

Re-evaluation date:

Evaluator(s)

Nikki Valentine
California Invasive Plant Council
nvalentine@cal-ipc.org

List committee members

Justin Valliere
Jutta Burger
Elizabeth Brusati
Umaina Khan

General Comments

There is an 1895 CCH record in Calflora, but this record seems questionable so I discounted it as the earliest record in California.

Table 2. Criteria, Section, and Overall Scores

Overall Score? Moderate

Alert Status? Alert

Documentation? 2.5 out of 5

Score

Documentation

1.1

?Impact on abiotic ecosystem processes

B. Moderate

Reviewed Scientific Publication

Impact?
Four-part score BBBD Total Score
B

1.2

?Impact on plant community

B. Moderate

Reviewed Scientific Publication

1.3

?Impact on higher trophic levels

B. Moderate

Reviewed Scientific Publication

1.4

?Impact on genetic integrity

D. None

No Information

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

A. Increases rapidly

Observational

2.3

?Recent trend in total area infested within state

C. Stable

Observational

2.4

?Innate reproductive potential
(see Worksheet A)

B. Moderate

Reviewed Scientific Publication

2.5

?Potential for human-caused dispersal

A. High

Observational

2.6

? Potential for natural long-distance dispersal

C. Rare

Observational

2.7

?Other regions invaded

C. Already invaded

Observational

3.1

?Ecological amplitude/Range
(see Worksheet C)

D. Narrow

Observational

Distribution?
Total Score C

3.2

?Distribution/Peak frequency
(see Worksheet C)

C. 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? Consider the impact on the natural range and variation of abiotic ecosystem processes and system-wide parameters in ways that significantly diminish the ability of native species to survive and reproduce. Alterations that determine the types of communities that can exist in a given area are of greatest concern. Examples of abiotic processes include: - fire occurrence, frequency, and intensity; - geomorphological changes such as erosion and sedimentation rates; - hydrological regimes, including soil water table; - nutrient and mineral dynamics, including salinity, alkalinity, and pH; - light availability (e.g. when an aquatic invader covers an entire water body that would otherwise be open). Select the one letter below that best describes this species' most severe impact on an abiotic ecosystem process: A. Severe, possibly irreversible, alteration or disruption of an ecosystem process. B. Moderate alteration of an ecosystem process. C. Minor alteration of an ecosystem process. D. Negligible perceived impact on an ecosystem process. U. Unknown.	B Reviewed Scientific Publication
Identify ecosystem processes impacted: Pistia stratiotes forms dense mats on the water surface in California (Calflora; Calflora entry; pers. comm. Ron Vanderhoff 2026). The dense mats block sunlight, reducing the growth of submerged macrophytes and planktonic algae; impede gas exchange at the air–water interface, reducing dissolved oxygen levels; reduce water flow; and release allelochemicals that inhibit algal growth (Gettys 2014; Howard et al 2026). Dense mats of Pistia stratiotes in California greatly reduces solar radiation into the water and likely increases organic matter load (pers. comm. Ron Vanderhoff 2026). Sedimentation may also be likely as a result of the increased organic matter load (Gómez-Ortiz et al. 2024). Sources of information: Calflora. Observation Search Pistia stratiotes. Accessed April 2026. Available Online: https://www.calflora.org/entry/observ.html?track=o#srch=t&taxon=Pistia+stratiotes&inma=f&cch=t&cnabh=t&inat=r&chk=t. Calflora. Plant Observation Entry: io146789. Accessed April 2026. Available online: https://www.calflora.org/entry/occdetail.html?seq_num=io146789. Gettys, Lyn A. 2014. Biology and Control of Aquatic Plants: Chapter 2:12. University of Florida FLREC, Davie FL. Available online: https://aquatics.org/bmpchapters/2.12%20Waterlettuce.pdf. Gómez-Ortiz, Y., Domínguez-Vega, H., Soria-Díaz, L., Rubio-Blanco, T., Astudillo-Sánchez, C. C., Mundo, V., & Sunny, A. 2024. Negative effects of agricultural open-channel irrigation system on vertebrate populations in central Mexico. PeerJ, 12, e17818. https://doi.org/10.7717/peerj.17818. Howard, V., E. Baker, J. Li,P. Alsip and J. Redinger, 2026, Pistia stratiotes L.: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI, https://nas.er.usgs.gov/queries/greatlakes/FactSheet.aspx?Species_ID=1099&Potential=Y&Type=2&HUCNumber, Revision Date: 12/30/2025, Access Date: 5/5/2026
Question 1.2 Impact on plant community composition, structure, and interactions? Consider the cumulative ecological impact of this species to the plant communities it invades. Give more weight to changes in plant composition, structure, and interactions that involve rare or keystone species or rare community types. Examples of severe impacts include: - formation of stands dominated (>75% cover) by the species; - occlusion (>75% cover) of a native canopy, including a water surface, that eliminates or degrades layers below; - significant reduction or extirpation of populations of one or more native species. Examples of impacts usually less than severe include: - reduction in propagule dispersal, seedling recruitment, or survivorship of native species; - creation of a new structural layer, including substantial thatch or litter, without elimination or replacement of a pre-existing layer; - change in density or depth of a structural layer; - change in horizontal distribution patterns or fragmentation of a native community; - creation of a vector or intermediate host of pests or pathogens that infect native plant species. Select the one letter below that best describes this species' impact on community composition, structure and interactions: A. Severe alteration of plant community composition, structure, or interactions. B. Moderate alteration of plant community composition. C. Minor alteration of community composition. D. Negligible impact known; causes no perceivable change in community composition, structure, or interactions. U. Unknown.	B Reviewed Scientific Publication
Identify type of impact or alteration: Pistia stratiotes forms dense mats on the the water surface in California (Calflora; Calflora entry). Dense populations of Pistia stratiotes form monocultures on the water surface that outcompete other vegetation, reducing plant diversity (Gettys 2014). The dense mats limit the light that can reach native submerged plants; impede gas exchange at the air–water interface, reducing dissolved oxygen levels; reduce water flow; and release allelochemicals that inhibit algal growth (Gettys 2014; Howard et al 2026). Sources of information: Calflora. Observation Search Pistia stratiotes. Accessed April 2026. Available Online: https://www.calflora.org/entry/observ.html?track=o#srch=t&taxon=Pistia+stratiotes&inma=f&cch=t&cnabh=t&inat=r&chk=t. Calflora. Plant Observation Entry: io146789. Accessed April 2026. Available online: https://www.calflora.org/entry/occdetail.html?seq_num=io146789. Gettys, Lyn A. 2014. Biology and Control of Aquatic Plants: Chapter 2:12. University of Florida FLREC, Davie FL. Available online: https://aquatics.org/bmpchapters/2.12%20Waterlettuce.pdf
Question 1.3 Impact on higher trophic levels? Consider the cumulative impact of this species on the animals, fungi, microbes, and other organisms in the communities that it invades. Although a non-native species may provide resources for one or a few native species (e.g. by providing food, nesting sites, etc.), the ranking should be based on the species' net impact on all native species. Give more weight to changes in composition and interactions involving rare or keystone species or rare community types. Examples of severe impacts include: - extirpation or endangerment of an existing native species or population; - elimination or significant reduction in native species' nesting or foraging sites, cover, or other critical resources (i.e., native species habitat), including migratory corridors. Examples of impacts that are usually less than severe include: - minor reduction in nesting or foraging sites, cover, etc. for native animals; - minor reduction in habitat connectivity or migratory corridors; - interference with native pollinators; - injurious components, such as awns or spines that damage the mouth and gut of native wildlife species, or production of anti-digestive or acutely toxic chemical that can poison native wildlife species. Select the one letter below that best describes this species' impact on community composition and interactions: A. Severe alteration of higher trophic populations, communities, or interactions. B. Moderate alteration of higher trophic level populations, communities, or interactions. C. Minor alteration of higher trophic level populations, communities or interactions. D. Negligible impact; causes no perceivable change in higher trophic level populations, communities, or interactions. E. Unknown.	B Reviewed Scientific Publication
Identify type of impact or alteration: Pistia stratiotes forms dense mats on the the water surface in California (Calflora; Calflora entry). Dense Pistia stratiotes populations block the air-water interface, which reduces dissolved oxygen and can make the system uninhabitable to fish and other aquatic fauna (Gettys 2014; North Carolina Extension Gardener). Dense Pistia stratiotes populations reduce plant diversity, which also eliminates habitats for animals that depend on native plants for shelter, nesting, and food (Gettys 2014). There are several species of mosquitos that breed in water held in the rosettes of waterlettuce (Gettys 2014). Sources of information: Calflora. Observation Search Pistia stratiotes. Accessed April 2026. Available Online: https://www.calflora.org/entry/observ.html?track=o#srch=t&taxon=Pistia+stratiotes&inma=f&cch=t&cnabh=t&inat=r&chk=t. Calflora. Plant Observation Entry: io146789. Accessed April 2026. Available online: https://www.calflora.org/entry/occdetail.html?seq_num=io146789. Gettys, Lyn A. 2014. Biology and Control of Aquatic Plants: Chapter 2:12. University of Florida FLREC, Davie FL. Available online: https://aquatics.org/bmpchapters/2.12%20Waterlettuce.pdf
Question 1.4 Impact on genetic integrity? Consider whether the species can hybridize with and influence the proportion of individuals with non-native genes within populations of native species. Mechanisms and possible outcomes include: - production of fertile or sterile hybrids that can outcompete the native species; - production of sterile hybrids that lower the reproductive output of the native species. Select the one letter below that best describes this species' impact on genetic integrity: A. Severe (high proportion of individuals). B. Moderate (medium proportion of individuals). C. Minor (low proportion of individuals). D. No known hybridization. U. Unknown.	D No Information
There is no known hybridization with native species. Pistia stratiotes is the only member of the genus. Although Pistia stratiotes' native range is debated, the species is likely native to Florida (USFWS 2018). The haplotype identified in Huntington Beach was not native to the western US (pers comm. Dr. Paul Madier 2024). Sources of information: USFWS. 2018. Water Lettuce (Pistia stratiotes) Ecological Risk Screening Summary. Online: https://www.fws.gov/sites/default/files/documents/Ecological-Risk-Screening-Summary-Water-Lettuce.pdf. Accessed July 2026.
Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance in establishment? Assess this species' dependence on disturbance: both human and natural: for establishment in wildlands. Examples of anthropogenic disturbances include: - grazing, browsing, and rooting by domestic livestock and feral animals; - altered fire regimes, including fire suppression; - cultivation; - silvicultural practices; - altered hydrology due to dams, diversions, irrigation, etc.; - roads and trails; - construction; - nutrient loading from fertilizers, runoff, etc. Examples of natural disturbance include: - wildfire; - floods; - landslides; - windthrow; - native animal activities such as burrowing, grazing, or browsing. Select the first letter in the sequence below that describes the ability of this species to invade wildlands: A. Severe invasive potential: this species can establish independent of any known natural or anthropogenic disturbance. B. Moderate invasive potential: this species may occasionally establish in undisturbed areas but can readily establish in areas with natural disturbances. C. Low invasive potential: this species requires anthropogenic disturbance to establish. D. No perceptible invasive potential: this species does not establish in wildlands (though it may persist from former cultivation). U. Unknown.	A Observational
Describe role of disturbance: Pistia stratiotes inhabits standing and slow-moving bodies of water (Calflora). In California this species has been reported in isolated bodies of water, such as ponds and lakes, or eddies along moving water (Calflora). Due to its current isolated distribution, the species is unlikely to establish without natural or anthropogenic disturbance. Pistia stratiotes plants have been found in California within outfall and drain pipes and drainage canals (Calflora Entry: io146789 2026). Pistia stratiotes is likely to be spread through flooding since there have been observations reported in Smiley Lagoon downstream from known infestations after storms (Calflora entry). Pistia stratiotes rosettes can become caught on boat trailers or in live wells (Gettys 2014). Pistia stratiotes is also spread as a result of escapes from cultivation and intentional release (Gettys 2014). Sources of information: Calflora. Plant Observation Entry: io146789. Accessed April 2026. Available online: https://www.calflora.org/entry/occdetail.html?seq_num=io146789. Gettys, Lyn A. 2014. Biology and Control of Aquatic Plants: Chapter 2:12. University of Florida FLREC, Davie FL. Available online: https://aquatics.org/bmpchapters/2.12%20Waterlettuce.pdf
Question 2.2 Local rate of spread with no management? Assess this species' rate of spread in existing localized infestations where the proportion of available habitat invaded is still small when no management measures are implemented. Select the one letter below that best describes the rate of spread: A. Increases rapidly (doubling in <10 years) B. Increases, but less rapidly C. Stable D. Declining U. Unknown	A Observational
Describe rate of spread: A population in Orange County increased from only a few individuals to thousands covering most of the water surface over a two-year period (Calflora Entry: mu1575). In China, Pistia stratiotes was able to grow twice its biomass in 2 to 3 days under temperature ranges of 22-30 ° C, growing up to 100,000 plants in one month (Liu and Yu 2025). Sources of information: Calflora. Plant Observation Entry: mu1575. Accessed April 2026. Available online: https://www.calflora.org/entry/poe.html#vrid=mu1575. Liu, S., & Yu, L. 2025. Invasive water lettuce (Pistia Stratiotes) increase CO2/CH4 emissions from a subtropical lake in Huixian wetland (Southwest China). Journal of Freshwater Ecology, 40(1). Online: https://doi.org/10.1080/02705060.2025.2516504.
Question 2.3 Recent trend in total area infested within state? Assess the overall trend in the total area infested by this species statewide. Include current management efforts in this assessment and note them. Select the one letter below that best describes the current trend: A. Increasing rapidly (doubling in total range statewide in <10 years) B. Increasing, but less rapidly C. Stable D. Declining U. Unknown	C Observational
Describe trend: Pistia stratiotes has mostly been reported in isolated bodies of water. Once it has infested a body of water its local spread rate is quite fast, but the species does not disperse to new bodies of water as quickly. There are less than 20 occurrences reported in Calflora (Calflora). Most populations are in southern California. The earliest observation in California is from 1944 in Imperial County (Calflora). The dense infestations in Huntington Beach Central Park and Echo Park have been under management, and these populations have decreased significantly (Calflora). Sources of information: Calflora. Accessed April 2026. Available online: https://www.calflora.org/entry/observ.html?track=o#srch=t&taxon=Pistia+stratiotes&cols=0,3,62,37,14,39,11,45,42&chk=t&cch=t&cnabh=t&inat=r.
Question 2.4 Innate reproductive potential? Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.	B Reviewed Scientific Publication
Describe key reproductive characteristics: Pistia stratiotes spreads by both seed and vegetative reproduction. Pistia stratiotes rapidly produces new daughter plants from horizontally growing stolons throughout the warm growing season (Gettys 2014). Additionally, Pistia stratiotes can reportedly self-pollinate and outcross (Haynes 1988). Pistia stratiotes populations can be composed of as many as 100 plants per square foot (Gettys 2014). Each plant produces multiple fruits and each 2 mm-long fruit can contain up to 20 tiny, golden-brown seeds, making it likely to produce over 1,000 viable seeds per square meter in dense infestations (Gettys 2014). Most seeds remain in the upper 2 inches of sediments and germination can be greater than 90% but it is not known how long the seeds remain viable (Gettys 2014). There has been conflicting evidence on whether Pistia stratiotes produces seed. Reports of seed-producing come from Florida and outside the US. Although this species is known to reproduce from seed outside of California, there is no evidence if this species produces seed in California. Seed reproduction can be important in temperate climates since Pistia stratiotes is killed by freezing temperatures and recolonization in spring may be dependent on the seed bank established during the previous growing seasons (Gettys 2014). Sources of information: Calflora. Plant Observation Entry: io146789. Accessed April 2026. Available online: https://www.calflora.org/entry/occdetail.html?seq_num=io146789 Gettys, Lyn A. 2014. Biology and Control of Aquatic Plants: Chapter 2:12. University of Florida FLREC, Davie FL. Available online: https://aquatics.org/bmpchapters/2.12%20Waterlettuce.pdf Haynes, R. R. 1988. Reproductive Biology of Selected Aquatic Plants. Annals of the Missouri Botanical Garden, 75(3), 805–810. https://doi.org/10.2307/2399368
Question 2.5 Potential for human-caused dispersal? Assess whether this species is currently spread: or has high potential to be spread: by direct or indirect human activity. Such activity may enable the species to overcome natural barriers to dispersal that would not be crossed otherwise, or it may simply increase the natural dispersal of the species. Possible mechanisms for dispersal include: - commercial sales for use in agriculture, ornamental horticulture, or aquariums; - use as forage, erosion control, or revegetation; - presence as a contaminant (seeds or propagules) in bulk seed, hay, feed, soil, packing materials, etc.; - spread along transportation corridors such as highways, railroads, trails, or canals; - transport on boats or boat trailers. Select the one letter below that best describes human-caused dispersal and spread: A. High: there are numerous opportunities for dispersal to new areas. B. Moderate: human dispersal occurs, but not at a high level. C. Low: human dispersal is infrequent or inefficient. D. Does not occur. U. Unknown.	A Observational
Identify dispersal mechanisms: There are numerous human-cause dispersal opportunities for Pistia stratiotes. Pistia stratiotes is spread as a result of escapes from cultivation (Gettys 2014). The species has been reported in nursery stock in California (Calflora). Rosettes can easily become caught on boat trailers or in live wells (Gettys 2014). Pistia stratiotes plants have been found in California within outfall and drain pipes and drainage canals (Calflora Entry: io146789 2026). Additionally, Pistia stratiotes may have been intentionally planted in some of the isolated ponds where it has been found. Sources of information: Calflora. Observation Search Pistia stratiotes. Accessed April 2026. Available Online: https://www.calflora.org/entry/observ.html? Gettys, Lyn A. 2014 Biology and Control of Aquatic Plants: Chapter 2:12. University of Florida FLREC, Davie FL. Available online: https://aquatics.org/bmpchapters/2.12%20Waterlettuce.pdf
Question 2.6 Potential for natural long-distance dispersal? We have chosen 1 km as the threshold of "long-distance." Assess whether this species is frequently spread, or has high potential to be spread, by animals or abiotic mechanisms that can move seed, roots, stems, or other propagules this far. The following are examples of such natural long-distance dispersal mechanisms: - the species' fruit or seed is commonly consumed by birds or other animals that travel long distances; - the species' fruits or seeds are sticky or burred and cling to feathers or hair of animals; - the species has buoyant fruits, seeds, or other propagules that are dispersed by flowing water; - the species has light propagules that promote long-distance wind dispersal; - The species, or parts of it, can detach and disperse seeds as they are blown long distances (e.g., tumbleweed). Select the one letter below that best describes natural long-distance dispersal and spread: A. Frequent long-distance dispersal by animals or abiotic mechanisms. B. Occasional long-distance dispersal by animals or abiotic mechanisms. C. Rare dispersal more than 1 km by animals or abiotic mechanisms. D. No dispersal of more than 1 km by animals or abiotic mechanisms. U. Unknown.	C Observational
Identify dispersal mechanisms: Pistia stratiotes is unlikely to disperse over 1 km without a disturbance event or human interference. The species inhabits still or slow-moving water and is mostly reported in closed bodies of water in California. Pistia stratiotes produces new plants from horizontally growing stolons (Gettys 2014). Pistia stratiotes may spread downstream during a flooding event. As there have been no reports of animals dispersing the species, Pistia stratiotes would require human disturbance or interference to spread to new bodies of water. Sources of information: Calflora. Observation Search Pistia stratiotes. Accessed April 2026. Available Online: https://www.calflora.org/entry/observ.html? Gettys, Lyn A. 2014 Biology and Control of Aquatic Plants: Chapter 2:12. University of Florida FLREC, Davie FL. Available online: https://aquatics.org/bmpchapters/2.12%20Waterlettuce.pdf
Question 2.7 Other regions invaded? Assess whether this species has invaded ecological types in other states or countries outside its native range that are analogous to ecological types not yet invaded in your state (see Worksheets B, C, and D for California, Arizona, and Nevada, respectively, in Part IV for lists of ecological types). This information is useful in predicting the likelihood of further spread within your state. Select the one letter below that best describes the species' invasiveness in other states or countries, outside its native range. A. This species has invaded 3 or more ecological types elsewhere that exist in your state and are as yet not invaded by this species (e.g. it has invaded Mediterranean grasslands, savanna, and maquis in southern Europe, which are analogous to California grasslands, savanna, and chaparral, respectively). B. Invades 1 or 2 ecological types that exist but are not yet invaded in your state. C. Invades elsewhere but only in ecological types that it has already invaded in the state. D. Not known as an escape anywhere else. U. Unknown.	C Observational
Identify other regions: Pistia stratiotes inhabits slow-moving rivers and reservoirs, irrigation channels, ponds, lakes, canals and ditches, rice paddies, and ephermal waters (EPPO Bulletin 2017). The ecological types that Pisitia stratiotes inhabits are already invaded in California. Pistia stratiotes in California occurs in ponds and lakes (e.g. Talbot Lake), creeks and rivers (e.g. San Diego River), and in brackish water (e.g. Smiley Lagoon) (Calflora). The only occurrence in brackish or marine water was an occurrence in Smiley Lagoon after a storm and the population may have been washed downstream (Calflora). Sources of information: Calflora. Observation Search Pistia stratiotes. Accessed April 2026. Available Online: https://www.calflora.org/entry/observ.html? EPPO Bulletin. 2017. Pistia stratiotes. Available online: https://onlinelibrary.wiley.com/doi/10.1111/epp.12429 Gettys, Lyn A. 2014 Biology and Control of Aquatic Plants: Chapter 2:12. University of Florida FLREC, Davie FL. Available online: https://aquatics.org/bmpchapters/2.12%20Waterlettuce.pdf
Section 3: Distribution
Question 3.1 Ecological amplitude/Range? Refer to Worksheet C and select the one letter below that indicates the number of different ecological types that this species invades. A. Widespread: the species invades at least three major types or at least six minor types. B. Moderate: the species invades two major types or five minor types. C. Limited: the species invades only one major type and two to four minor types. D. Narrow: the species invades only one minor type. U. Unknown.	D Observational
The species is not cold-hardy and rarely establishes permanent populations in temperate areas (Gettys 2014). Water lettuce will survive moderate freezes but requires temperatures of greater than 50 °F to produce new growth (Gettys 2014). There are not many observations of Pistia stratiotes outside southern California. Most Pistia stratiotes observations occur in Orange, Los Angeles, and San Diego counties (Calflora). Pistia stratiotes occurs in standing or slow water in California (Calflora). The earliest observation in California is from 1944 in Imperial County (Calflora). Sources of information: Calflora. Observation Search Pistia stratiotes. Accessed April 2026. Available Online: https://www.calflora.org/entry/observ.html?track=o#srch=t&taxon=Pistia+stratiotes&inma=f&cch=t&cnabh=t&inat=r&chk=t.
Question 3.2 Distribution/Peak frequency? To assess distribution, record the letter that corresponds to the highest percent infested score entered in Worksheet C for any ecological type.	C Observational
Describe distribution: There are reported observations of Pistis stratiotes in California in ponds and lakes (e.g. Talbot Lake), creeks and rivers (e.g. San Diego River), and in brackish water (e.g. Smiley Lagoon) (Calflora). The only occurrence in brackish or marine water was a one-time occurrence in Smiley Lagoon after a storm and the organisms may have been washed downstream (Calflora entry in:9453078). Sources of information: Calflora. Observation Search Pistia stratiotes. Accessed April 2026. Available Online: https://www.calflora.org/entry/observ.html?track=o#srch=t&taxon=Pistia+stratiotes&inma=f&cch=t&cnabh=t&inat=r&chk=t. Calflora. Plant Observation Entry: in:9453078. Accessed April 2026. Available online: https://www.calflora.org/entry/poe.html#vrid=in:9453078

Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less	Yes
Dense infestations produce >1,000 viable seed per square meter	Unknown
Populations of this species produce seeds every year.	Unknown
Seed production sustained over 3 or more months within a population annually	Unknown
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	Yes
Fragments easily and fragments can become established elsewhere	Yes
Resprouts readily when cut, grazed, or burned	Yes
Total points:	5
Total unknowns:	5
Total score:	B? Scoring Criteria for Worksheet A A. High reproductive potential (6 or more points). B. Moderate reproductive potential (4-5 points). C. Low reproductive potential (3 points or less and less than 3 Unknowns). U. Unknown (3 or fewer points and 3 or more Unknowns).

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? A means >50% of type occurrences are invaded; B means 20% to 50%; C means 5% to 20%; D means present but <5%; U means unknown (unable to estimate percentage of occurrences invaded)
Marine Systems	marine systems	U, Unknown
Freshwater and Estuarine	lakes, ponds, reservoirs	D, < 5%
Aquatic Systems	rivers, streams, canals	D, < 5%
Aquatic Systems	estuaries	U, Unknown
Dunes	coastal	U, Unknown
	desert	U, Unknown
	interior	U, Unknown
Scrub and Chaparral	coastal bluff scrub	U, Unknown
	coastal scrub	U, Unknown
	Sonoran desert scrub	U, Unknown
	Mojavean desert scrub (incl. Joshua tree woodland)	U, Unknown
	Great Basin scrub	U, Unknown
	chenopod scrub	U, Unknown
	montane dwarf scrub	U, Unknown
	Upper Sonoran subshrub scrub	U, Unknown
	chaparral	U, Unknown
Grasslands, Vernal Pools, Meadows, and other Herb Communities	coastal prairie	U, Unknown
	valley and foothill grassland	U, Unknown
	Great Basin grassland	U, Unknown
	vernal pool	U, Unknown
	meadow and seep	U, Unknown
	alkali playa	U, Unknown
	pebble plain	U, Unknown
Bog and Marsh	bog and fen	U, Unknown
Bog and Marsh	marsh and swamp	U, Unknown
Riparian and Bottomland habitat	riparian forest	U, Unknown
	riparian woodland	U, Unknown
	riparian scrub (incl.desert washes)	U, Unknown
Woodland	cismontane woodland	U, Unknown
	piñon and juniper woodland	U, Unknown
	Sonoran thorn woodland	U, Unknown
Forest	broadleaved upland forest	U, Unknown
	North Coast coniferous forest	U, Unknown
	closed cone coniferous forest	U, Unknown
	lower montane coniferous forest	U, Unknown
	upper montane coniferous forest	U, Unknown
	subalpine coniferous forest	U, Unknown
Alpine Habitats	alpine boulder and rock field	U, Unknown
Alpine Habitats	alpine dwarf scrub	U, Unknown
	Amplitude (breadth):	C
	Distribution (highest score):	D

Infested Jepson Regions

Click here for a map of Jepson regions

Central West
Great Valley
Northwest
Southwest
Sonoran Desert