Wild blackberries (Rubus spp. )
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Most species of wild blackberry, also called brambles, are important sources of food and cover for many birds and mammals. Several species, however, are also considered weeds. Two of these are non-natives, cutleaf blackberry, Rubus laciniatus, and Himalaya blackberry, Rubus armeniacus (=R. procerus, R. discolor). Himalaya blackberry is common throughout California, except in deserts, to about 5200 feet (1600 m). Cutleaf blackberry is scattered in the Cascade Range, Sierra Nevada, San Francisco Bay region, and Penisular Ranges up to an elevation of about 6200 feet (1900 m).
In addition, three native species can also be weeds under certain conditions. For example, Western thimbleberry, Rubus parviflorus, competes with conifers during establishment in reforested areas, and Pacific blackberry, Rubus ursinus (=R. vitifolius) can infest areas adjacent to streams and ditches. Western thimbleberry is found throughout California up to about 8200 feet (2500 m), except in deserts, the Central Valley, and Modoc Plateau. Pacific blackberry is common throughout California up to about 4900 feet (1500 m), except deserts and the Great Basin. These, as well as western raspberry, Rubus leucodermis, can be weedy in disturbed non-natural systems such as pastures and tree plantations. Western raspberry is found in the mountainous regions of California up to about 7800 feet (2400 m), except for the coast, deserts, and Central Valley.
Of these weedy species, the most common, vigorous, and troublesome is Himalaya blackberry. Typically, first year stems grow in length. In the second year, stems produce flowers, fruits, and often have leaves with a varying numbers of leaflets. Fruiting stems usually die after they put out fruit.
Of the four weedy wild blackberries, thimbleberry is the only nonvining species. It also lacks prickly stems and has a simple leaf (no leaflets). Both Himalaya and cutleaf blackberry have five-angled stems, but Himalaya blackberry can easily be distinguished from the other wild blackberries by its five distinct leaflets, each leaflet toothed and generally oval in shape. By comparison, cutleaf blackberry has five very deeply lobed leaflets and California blackberry has only three leaflets. The majority of roots grow down to approximately 1–1/2 feet (50 cm). Some may even grow down about 6–1/2 feet (2 m) deep.
Flowers have five white to pinkish petals. Bloom times for these species are:
- Himalaya blackberry, May through September;
- cutleaf blackberry, May through July;
- western raspberry, April through July;
- western thimbleberry, March through August;
- Pacific blackberry, March through July.
The blackberry fruit is an aggregate of many, tiny, fleshy, one-seeded fruit that adhere to the fruit bearing parts. Whereas raspberries, including western thimbleberry, have fruits that separate from the fruit bearing parts, to form a cap-shaped fruit. Typically, fruits disperse to great distances by animals, particularly birds.
Wild blackberries reproduce by seed, crown and rhizome (horizontal stem) sprouts, and stem tip rooting (except western thimbleberry).