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Have you seen Florida prickly blackberry (Rubus argutus)?
Hawaii Early Detection Network Priority Pest for the island Kauai


Rubus argutus leaf shape
Florida prickly blackberry leaves have 3-5 leaflets Image: 2002 Steve Baskauf
Rubus argutus
Flowers with 5 petals
Rubus ellipticus flower
Florida prickly blackberry fruit
Images (center and right): Forest & Kim Starr

Identification: Florida prickly blackberry is an erect, arching, thorned shrub which was introduced to Hawai'i in 1894 and has become widespread and naturalized on all main Hawaiian Islands except Kauai. It is a rambling shrub that grows up to 15-20 feet tall and has 5 angled stems that are covered with slightly curved prickles (.3 in long). Leaves grow in leaflet grouping of 3 (sometimes 5) with a terminal leaflet that is 3-5 in long and 1-3 in wide. Leaflets have a coarsely serrate edge, giving rise to this plants other name, sawtooth raspberry. It produces numerous small, white flowers which develop into black berries.
Impacts: Florida prickly blackberry can become a backyard, pasture, and wildland pest where it forms dense, clonal thickets that will smother other plants and impede the movement of people and animals. It thrives in a variety of Hawaiian habitats from 950 ft. to over 8,000 ft. in elevation. It is hard to kill once established.
Dispersal Mechanism: This raspberry is spread by birds and mammals that eat the fruit. It can also spread vegetatively by the rooting of aerial shoots wherever the stems bend over and touch the ground. If you see it anywhere on Kauai besides Koke'e, let someone know!

More information about this pest external link


Florida prickly blackberry look-alikes:


Himalayan blackberry (Rubus discolor):
Himalayan blackberry is another invasive Rubus that can be confused with Florida prickly raspberry. Himalayan raspberry also has white flowers and black berries, but has distinctive leaflets of 5 in a palmate arrangement. This blackberry is found throughout Hawaii, except for Kauai, Lanai, and Molokai.

THIS LOOK-ALIKE IS ALSO A PEST!

Rubus discolor

Blackberry (Rubus armeniacus) often has leaflets of 5 in a palmate arrangement.

Akala (Rubus hawaiiensis):
The native Hawaiian raspberry can be distinguished by its pale prickle covered stalks and PINK FLOWERS. Akala is the only raspberry/blackberry that loses its leaves in the winter.

Rubus hawaiiensis

Akala (Rubus hawaiiensis)

Last Updated: Monday January 30 2012. If you have any questions about the Hawaii Early Detection Network contact reportapest-maui@lists.hawaii.edu.
Funding and support for this project was made possible by the Hawai'i Invasive Species Council, the USDA Forest Service State and Private Forestry assistance, and University of Hawai'i-Pacific Cooperative Studies Unit.