Hyparrhenia hirta Risk – California Invasive Plant Council

Created by: Elizabeth D. Brusati
Created on: Wednesday, Jan 27th, 2016

Evaluation Summary

Summary:

General Evaluation Information

Date of Evaluation:

March 16, 2016

Evaluation Time (hrs):

3 Hours

Evaluation Status:

Completed

Plant Information

Plant:

Hyparrhenia hirta

Plant Material:

If the plant is a cultivar, and if the cultivar's behavior differs from its parent's (behavior), explain how:

Regional Information

Region Name:

California

Climate Matching Map

These maps were built using a toolkit created in collaboration between GreenInfo Network, PlantRight, Cal-IPC, and Agricultural Sustainability Institute at UC Davis.

Link to Climate Matching Map:

Climate Matching Maps PDF:

Invasive History and Climate Matching

1. Has the species (or cultivar or variety, if applicable; applies to subsequent "species" questions) become naturalized where it is not native?

Yes or No:

Yes

Points:

Confidence Level:

Very High

Answer / Justification:

California and Texas, widely naturalized in southern and eastern Australia. GBIF also shows locations in Western Australia and Central America. USDA ARS simply says naturalized without specifying where.

Reference(s):

USDA NRCS (2015). PLANTS Database.

Queensland Government (2011). Weeds of Australia Biosecurity Queensland Edition.

GBIF (0). Global Biodiversity Information Facility (GBIF).

2. Is the species (or cultivar or variety) noted as being naturalized in the US or world in a similar climate?

Yes or No:

Yes

Points:

Confidence Level:

Very High

Answer / Justification:

Naturalized in two California counties. Some locations in Australia match California's climate. A weed of roadsides, disturbed sites, waste areas, higher quality pastures, grasslands, rangelands and open woodlands in temperate, sub-tropical and semi-arid regions.

Reference(s):

Calflora (2015). Calflora.

GBIF (0). Global Biodiversity Information Facility (GBIF).

-IPC, C. (2016). Cal-IPC global map of climate areas matching California.

3. Is the species (or cultivar or variety) noted as being invasive in the U.S. or world?

Yes or No:

Yes

Points:

Confidence Level:

Very High

Answer / Justification:

Listed as a noxious weed in South Australia, where it is required to be controlled. Also considered invasive in New South Wales, Queensland, Victoria, W. Australia. A weed of roadsides, disturbed sites, waste areas, higher quality pastures, grasslands, rangelands and open woodlands in temperate, sub-tropical and semi-arid regions.

Reference(s):

Queensland Government (2011). Weeds of Australia Biosecurity Queensland Edition.

4. Is the species (or cultivar or variety) noted as being invasive in the US or world in a similar climate?

Yes or No:

Yes

Points:

Confidence Level:

Very High

Answer / Justification:

Reference(s):

Queensland Government (2011). Weeds of Australia Biosecurity Queensland Edition.

GBIF (0). Global Biodiversity Information Facility (GBIF).

-IPC, C. (2016). Cal-IPC global map of climate areas matching California.

McArdle, S.L.., Nadolny C.., & Sindel B.M.. (2004). Invasion of native vegetation by Coolatai Grass Hyparrhenia hirta: impacts on native vegetation and management implications. Pacific Conservation Biology. 10, 49–56.

5. Are other species of the same genus (or closely related genera) invasive in a similar climate?

Yes or No:

Points:

Confidence Level:

High

Answer / Justification:

There are 15 other species listed in the Global Compendium of Weeds, mostly noted only as naturalized. Hyparrhenia rufa is the only other species with a number of citations. It is a problem in tropical South America, but this seems more tropical than California. Hyparrhenia rufa subsp. rufa is an environmental weed in Queensland and other parts of northern Australia but that does not match California's climate.

Reference(s):

Weber, E.. (2003). Invasive Plant Species of the World. 548.

Randall, R. (2012). A Global Compendium of Weeds. 2nd Edition..

Queensland Government (2011). Weeds of Australia Biosecurity Queensland Edition.

-IPC, C. (2016). Cal-IPC global map of climate areas matching California.

6. Is the species (or cultivar or variety) found predominately in a climate matching the region of concern?

Yes or No:

Yes

Points:

Confidence Level:

High

Answer / Justification:

H. hirta occurs in many locations around the Mediterranean that are similar to California, and also in southern Africa. The native range is mostly winter rainfall areas. GBIF map = http://www.gbif.org/species/2703243

Reference(s):

GBIF (0). Global Biodiversity Information Facility (GBIF).

-IPC, C. (2016). Cal-IPC global map of climate areas matching California.

Impact on Native Plants and Animals

7. Does this plant displace native plants and dominate (overtop or smother) the plant community in areas where it has established?

Yes or No:

Yes

Points:

Confidence Level:

High

Answer / Justification:

Spreading rapidly in southeastern Australia where it reduces the richness of native plants. Diversity and ground cover of native vascular plants are significantly reduced by heavy infestations of Hyparrhenia hirta.

Reference(s):

8. Is the plant noted as promoting fire and/or changing fire regimes?

Yes or No:

Yes

Points:

Confidence Level:

Medium

Answer / Justification:

No mention of this specifically. However, the fact that it is called thatching grass implies that it could form a layer of thatch that might increase fuel loads. Increases after fire. This website mentions that the species germination and growth is stimulated by smoke, but does not cite where they derive this from. Given grasses flammability and structure it seems likely that it does have an impact on fire regimes and is likely to increase frequency and spread if it invades communities that formerly were not grass dominated.https://florabase.dpaw.wa.gov.au/browse/profile/452

Reference(s):

Coleman, H., Brown K., & Bettink K. (2014). FloraBase: The Western Australia Flora.

9. Is the plant a health risk to humans or animals/fish? Has the species been noted as impacting grazing systems?

Yes or No:

Points:

Confidence Level:

High

Answer / Justification:

"Not favored by livestock but a useful feed if not allowed to seed." Was originally introduced as a forage grass.

Reference(s):

Queensland Government (2011). Weeds of Australia Biosecurity Queensland Edition.

10. Does the plant produce impenetrable thickets, blocking or slowing movement of animals, livestock, or humans?

Yes or No:

Points:

Confidence Level:

Medium

Answer / Justification:

Forms dense infestations. Can grow as tall as 1.5m. Since it's a grass, it's difficult to say if infestations are impenetrable (compared to a shrub of that same height).

Reference(s):

Reproductive Strategies

11. Does this species (or cultivar or variety) reproduce and spread vegetatively?

Yes or No:

Points:

Confidence Level:

High

Answer / Justification:

Reproduces mainly by seed. The seed-heads are large leafy compound clusters (i.e. synflorescences) 15-40 cm or more long.

Reference(s):

Queensland Government (2011). Weeds of Australia Biosecurity Queensland Edition.

12. If naturally detached fragments from this plant are capable of producing new plants, is this a common method of reproduction for the plant?

Yes or No:

Yes

Points:

Confidence Level:

Medium

Answer / Justification:

Reproduces mainly by seed. Although this may not be a primary method of reproduction any rhizomatous grass that I am familiar with is able to reproduce from fragments, so this seems likely even if it rarely happens. - Tim Hyland

Reference(s):

Queensland Government (2011). Weeds of Australia Biosecurity Queensland Edition.

13. Does the species (or cultivar or variety) commonly produce viable seed?

Yes or No:

Yes

Points:

Confidence Level:

Very High

Answer / Justification:

Reproduces mainly by seed. The seed-heads are large leafy compound clusters (i.e. synflorescences) 15-40 cm or more long.

Reference(s):

Queensland Government (2011). Weeds of Australia Biosecurity Queensland Edition.

14. Does this plant produce copious viable seeds each year (> 1000)?

Yes or No:

Points:

Confidence Level:

Very Low

Answer / Justification:

Could not find information

Reference(s):

15. Is there significant germination (>25%) of seeds the next growing season, with no requirement of an infrequent environmental condition for seeds to germinate (i.e. fire) or long dormancy period?

Yes or No:

Yes

Points:

Confidence Level:

Medium

Answer / Justification:

At least one website cited a study that showed that seeds from this species were able to germinate under a wide variety of PH, diurnal fluctuation and light regimes. There was no mention of dormancy. - Comment by Tim Hyland. (I do not have citation)

Reference(s):

16. Does this plant produce viable seed within the first three years (for an herbaceous species) to five years (for a woody species) after germination?

Yes or No:

Yes

Points:

Confidence Level:

Medium

Answer / Justification:

Could not find information but a short juvenile period seems likely as it's a grass.

Reference(s):

17. Does this plant continuously produce seed for >3 months each year or does seed production occur more than once a year?

Yes or No:

Yes

Points:

Confidence Level:

Medium

Answer / Justification:

Flowers March-July in California. In Australia, flowering occurs throughout the year, but mainly during summer.

Reference(s):

Jepson Flora Project (2014). Jepson eFlora.

Queensland Government (2011). Weeds of Australia Biosecurity Queensland Edition.

Dispersal

18. Are the plant’s propagules frequently dispersed long distance (>100 m) by mammals or birds or via domestic animals?

Yes or No:

Yes

Points:

Confidence Level:

Medium

Answer / Justification:

Animals may disperse short distances (but no mention of longer dispersal).

Reference(s):

Queensland Government (2011). Weeds of Australia Biosecurity Queensland Edition.

19. Are the plant’s propagules frequently dispersed long distance (>100 m) by wind or water?

Yes or No:

Points:

Confidence Level:

Medium

Answer / Justification:

Can be spread short distances by wind, can float in water. Answering no because unsure how important these types of dispersal are.

Reference(s):

Queensland Government (2011). Weeds of Australia Biosecurity Queensland Edition.

20. Are the plant’s propagules frequently dispersed via contaminated seed (agriculture or wildflower packets), equipment, vehicles, boats or clothing/shoes?

Yes or No:

Yes

Points:

Confidence Level:

High

Answer / Justification:

Dispersed by vehicles, in mud, and in contaminated fodder. Spreads more rapidly along roads than away from roads, suggesting that seeds are being dispersed by vehicles (or the wind they generate) or road maintenance equipment.

Reference(s):

Queensland Government (2011). Weeds of Australia Biosecurity Queensland Edition.