Grevillea robusta Risk – California Invasive Plant Council

Created by: Elizabeth D. Brusati
Created on: Thursday, Apr 21st, 2016

Evaluation Summary

Summary:

General Evaluation Information

Date of Evaluation:

April 21, 2016

Evaluation Time (hrs):

2 Hours

Evaluation Status:

Completed

Plant Information

Plant:

Grevillea robusta

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:

Naturalized in California. Present in 8 counties according to Calflora. Native of Australia but widely introduced and naturalized in tropical and subtropical regions of the world. There are many points in GBIF. This species is cultivated for forestry. "The trees scatter their winged seeds and have become undesirable weeds in some pastures and rangelands of Hawaii, requiring eradication."

Reference(s):

Jepson Flora Project (2014). Jepson eFlora.

Calflora (2015). Calflora.

Little, Jr., E. L., & Skolman R. G. (2003). Common Forest Trees of Hawaii.

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 California. Present in 8 counties according to Calflora. There are many points in GBIF, including areas of South Africa that are similar to California.

Reference(s):

Jepson Flora Project (2014). Jepson eFlora.

Calflora (2015). Calflora.

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

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

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:

High

Answer / Justification:

Invasive in Jamaica, Zimbabwe, South Africa and Hawaii. In South Africa, invades forest edges, savannah and riparian areas. Hawaii: "The trees scatter their winged seeds and have become undesirable weeds in some pastures and rangelands of Hawaii, requiring eradication."

Reference(s):

Little, Jr., E. L., & Skolman R. G. (2003). Common Forest Trees of Hawaii.

[Anonymous] (2007). CABI Invasive Species Compendium.

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:

In South Africa, invades forest edges, savannah and riparian areas. A regulated weed in South Africa and a problem in Western Cape, Eastern Cape, KwaZulu-Natal, Gauteng, Limpopo and Mpumalanga.

Reference(s):

[Anonymous] (2012). Invasive Species South Africa.

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

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

Yes or No:

Yes

Points:

Confidence Level:

High

Answer / Justification:

There are numerous species of Grevillea listed in Randall 2012, although most have just a couple of references to it being naturalized or a weed. Grevillea banksii is invasive and a regulated plant in South Africa.

Reference(s):

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

[Anonymous] (2012). Invasive Species South Africa.

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

Yes or No:

Points:

Confidence Level:

Very High

Answer / Justification:

Based on locations in GBIF and description in CABI, it occurs mostly in areas that are more tropical than California. Map: http://www.gbif.org/species/2891791

Reference(s):

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

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

[Anonymous] (2007). CABI Invasive Species Compendium.

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:

Can displace native plant communities in South Africa. Extensive naturalized stands in Hawaii.

Reference(s):

Little, Jr., E. L., & Skolman R. G. (2003). Common Forest Trees of Hawaii.

[Anonymous] (2012). Invasive Species South Africa.

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

Yes or No:

Points:

Confidence Level:

High

Answer / Justification:

"G. robusta is vulnerable to fire and hence is excluded from the fire-prone Eucalyptus forests and grasslands that occupy much of its natural range."

Reference(s):

[Anonymous] (2007). CABI Invasive Species Compendium.

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:

No mention of toxicity in references, other than possible allelopathy. Can invade savannahs in South Africa but I found no mention of impacts to grazing specifically.

Reference(s):

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:

A tree that grows 40-70 ft high with many branches. Described as invasive but I did not find data to support it creating impenetrable stands.

Reference(s):

Little, Jr., E. L., & Skolman R. G. (2003). Common Forest Trees of Hawaii.

Reproductive Strategies

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

Yes or No:

Yes

Points:

Confidence Level:

High

Answer / Justification:

Can reproduce vegetatively through root suckering.

Reference(s):

[Anonymous] (2007). CABI Invasive Species Compendium.

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:

Points:

Confidence Level:

High

Answer / Justification:

This is a tree so would be unlikely to have this form of reproduction.

Reference(s):

Little, Jr., E. L., & Skolman R. G. (2003). Common Forest Trees of Hawaii.

[Anonymous] (2012). Invasive Species South Africa.

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

Yes or No:

Yes

Points:

Confidence Level:

Very High

Answer / Justification:

Producing many seeds.

Reference(s):

Little, Jr., E. L., & Skolman R. G. (2003). Common Forest Trees of Hawaii.

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

Yes or No:

Yes

Points:

Confidence Level:

Medium

Answer / Justification:

Produces "great quantities" of seeds but I do not have a specific number. There are about 40,000 viable seeds/kg, but again, not sure how that translates to seeds per plant.

Reference(s):

Little, Jr., E. L., & Skolman R. G. (2003). Common Forest Trees of Hawaii.

[Anonymous] (2007). CABI Invasive Species Compendium.

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:

High

Answer / Justification:

Described as a prolific seeder. No mention of any special requirements in the references I found.

Reference(s):

[Anonymous] (2007). CABI Invasive Species Compendium.

Little, Jr., E. L., & Skolman R. G. (2003). Common Forest Trees of Hawaii.

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:

Described as an early and prolific seed producer so I am assuming yes.

Reference(s):

[Anonymous] (2007). CABI Invasive Species Compendium.

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:

Points:

Confidence Level:

High

Answer / Justification:

"Flowering commences in October in lowland occurrences in the native range, and seed is mature by the end of December. At high elevations, flowering and seed production occur 4-6 weeks later (Harwood, 1992a)"

Reference(s):

[Anonymous] (2007). CABI Invasive Species Compendium.

Dispersal

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

Yes or No:

Points:

Confidence Level:

High

Answer / Justification:

wind-dispersed

Reference(s):

Little, Jr., E. L., & Skolman R. G. (2003). Common Forest Trees of Hawaii.

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

Yes or No:

Yes

Points:

Confidence Level:

Very High

Answer / Justification:

Winged seeds are dispersed by wind.

Reference(s):

Global Compendium of Weeds (GCW), Hawaiian Ecosystems at Risk (HEAR) project, Pacific Island Ecosystems at Risk (PIER) (2007). Invasive species information for Hawaii and the Pacific: Global Compendium of Weeds (GCW).

Little, Jr., E. L., & Skolman R. G. (2003). Common Forest Trees of Hawaii.

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

Yes or No:

Points:

Confidence Level:

High

Answer / Justification:

Winged seeds are dispersed by wind.

Reference(s):

Little, Jr., E. L., & Skolman R. G. (2003). Common Forest Trees of Hawaii.

Evaluation Notes

HEAR, Hawaii: http://www.hear.org/pier/species/grevillea_robusta.htm

Forest Trees of Hawaii: http://www.ctahr.hawaii.edu/forestry/trees/CommonTreesHI/CFT_Grevillea_robusta.pdf

GBIF: http://www.gbif.org/species/2891791