ALIEN PLANT INVADERS: HIMALAYAN AND EVERGREEN BLACKBERRY

From a series of articles on how to identify and manage some common invasive species on Salt Spring Island written by Jean Wilkinson, Stewardship Committee, Salt Spring Island Conservancy.

Blackberries are a wonderful fruit, and late summer finds many of us picking loads of them for pies, jams, jellies, wine, freezing and eating fresh. The native Trailing Blackberry is delicious, but the berries are small and not very plentiful. Most abundant are Himalayan and Evergreen blackberries, which were brought to North America in the late 1800’s.

Unfortunately, these exuberant plants can quickly spread and invade gardens as well as natural areas, creating big thickets and crowding out native plants. They are becoming a serious problem in many places, and with their sprawling growth many of the berries are impossible to reach!

To prevent blackberry bushes from taking over and still have plenty of fruit to enjoy, you can prune and train the plants. In the fall, winter or early spring cut out all canes that have already borne fruit. Cut the new canes (which flower and bear the next season) back to 1 or 2 metres long to encourage them to begin branching laterally. Tie these branches to a fence or trellis and prune back to 30 - 60 cm. A simple trellis can be made by running a few wires between two posts about 2 metres high.

A small patch of blackberries grown in a sunny area with moist soil and managed in this way will produce loads of berries that are easy to pick. Plants growing in other areas can be removed using the methods outlined below, in order to help preserve local biodiversity. Non-invasive species of blackberries are also available, and listed below. HIMALAYAN AND EVERGREEN BLACKBERRY– FACTS ABOUT THESE HORTICULTURAL BULLIES:

Identification – Rubus armeniacus, aka R. discolor, or R. procerus. Thick stems or canes up to 12 metres long with large hooked thorns grow up over other plants or structures and sprawl along the ground. Leaves are alternate and have 3 to 5 large oval leaflets, dark green on top and gray-green underneath. Clusters of white-pink five-petalled flowers yield large berries ripening from green to red to black. Evergreen blackberry (R. laciniatus) is similar but has deeply incised and jagged leaflets, greenish on the underside. (Native Trailing Blackberry (Rubus ursinus) has thin prostrate vines, small thorns and leaves with 3 parts.)

Impacts –out-compete native vegetation for sunlight and nutrients, and can create large impenetrable thickets which reduce access for people and grazing animals but provide hiding places for rabbits and rats.

Found –in disturbed sites along roads, fences, streams, forest edges and rights-of-way, and in range and pasture lands.

Spread – by seeds in the berries (distributed by birds), by root sprouts and by rooting cane tips.

Control – Start in new or small patches and later move into the more heavily infested areas. Young plants to 1 metre tall can be pulled by hand or weed wrench, most easily when the soil is moist. Canes in large established patches are best cut back from July to early October, when new tips are least likely to grow. Regular removal of top growth by mowing or cutting will eventually kill blackberry. To be most effective, dig out as much of the root as possible in winter or spring, monitor area and remove any sprouts in following years. Disposal – If no seeds are present, canes can be piled, compressed and left to slowly rot, but should be monitored for re- sprouting and re-rooting. If seeds are present, tarp plant parts and take to designated disposal site or landfill.

Alternatives – (Note * indicates plant is Drought Tolerant when established) Native berries: Thimbleberry* - Sun or shade, Moist soil Salmonberry*- Part or Full shade, Moist soil Black Huckleberry*- Part or full shade, Dry soil Evergreen Huckleberry – Part or Full shade, Moist or Dry soil Non-native: Marionberry; Boysenberry; Loganberry; Tayberry; Black Raspberry – Sun, Moist soil

More Info: Salt Spring Island Conservancy Stewardship Committee 250-537-4877, Coastal Invasive Species Committee www.coastalinvasivespecies.com , Invasive Species Council of B.C. www.bcinvasives.ca