Garden of Eden-Revisited
May 2, 2003
In a modern day interpretation of the story of Eve succumbing to temptation and taking that first mouth watering bite of the forbidden fruit; we would have a Metchosin family sitting down to their first of the season, wildly perfumed and fantastically flavoured blackberry crisp. It is hard to believe that something so exquisitely delicious can be so devastating for our environment, but given a moments inattention, it will destroy our little bit of Eden in it’s aggressive quest for global domination.
Himalayan (Rubus discolor) and evergreen (R. laciniatus) blackberry are introduced Eurasian weeds which tempt us with their ambrosia like qualities while transforming our native landscapes into thorny and impenetrable monocultures. Their long arching branches cascade 20 to 40 ft (6-12m) and where they touch the ground, new plants will form. Their rootstocks are large reservoirs which store the fuel needed to sustain their massive growth each season. Sharp, vicious thorns grow along the stems as well as on the leaves and leaf stems. Himalayan blackberry has leaves that branch like fingers from a grasping hand, with five large, oval, toothed leaflets; evergreen blackberry also has five leaflets which have very indented edges.
The Himalayan blackberry is the one most familiar to us as a favoured berry and noxious pest. It is the one you notice infesting hedgerows, meadows and parkland and it is partial to moist areas in either full sun or part shade. It’s habit of rampant growth quickly consumes most plants other than mature trees in it’s path. To be fair, it does offer food and shelter to birds and small mammals, although the original diversity of species has been greatly reduced. The birds are excellent dispersers of blackberry seed and the time spent inside the birds is thought to enhance the germination success of the seeds.
For those who wish to reclaim a portion of their original Eden, control of blackberries is a daunting prospect. There are several methods used to remove blackberries and they are the same for all species.
The first is physical control.
Small seedlings can be hand pulled.
For mature plants:
Remove the top growth in whatever manner is possible to you, with lopers, brush mowers or weedeaters. Mow repeatedly all year to prevent regrowth and deplete the energy reserves of the massive rootstocks. This can take three years so persistence is needed. Some suggest pouring boiling water over the cut stems at this point to try to kill off the roots. Mature plants can be hand dug, removing all roots to prevent resprouting. This should be undertaken in the wet season as the roots are easier to dislodge at this time. Disturb the soil as little as possible to discourage seedbank recruitment. The roots can be large and tenacious and the use of a pry bar, a three-clawed rake or a Pulaski (a tool that is half axe, half adz hoe that is used in making firelines) has been recommended. Pieces of cut root can resprout so be diligent.
In rocky, shallow soils goats are recommended, although they are the mammal equivalent of a non-selective herbicide and will also browse the native and other desirable plants.
The second is chemical control. These methods are endorsed by the Government of British Columbia in their Integrated Pest Management Manual for Landscape Pests in British Columbia (2000).
“The entire thicket must be mowed or cut down in May or early June to remove all woody top growth. The roots will sprout new shoots, which should be left to grow for the summer. In early September, treat the plants with the non-selective (can kill any type of plant) herbicide, glyphosate (Round-up or Vision). At that time of the year, the herbicide is readily translocated to the roots. The plants may not appear to be affected for some time, however, they do not grow back in the spring.” Never apply spray pesticides during windy conditions. Also from the BC Government, the Handbook for Pesticide Applicators and Dispensers (1995); “Glyphosate is quickly deactivated in soil, so no residue remains in soil to contaminate subsequent crops. It has a low acute toxicity to mammals, fish and wildlife, but may cause eye irritation. Rain within six hours of application reduces effectiveness.”
The use of herbicides should always be considered carefully and directions followed faithfully, using protective wear. Some people recommend using herbicides in a “cut and paint” manner. Within 5 to 20 minutes of cutting a weed stem, paint the cut area with the appropriate non-selective herbicide. This reduces the danger to humans and to other plants from spray drifting onto them.
Our native trailing blackberry (Rubus ursinus) or dewberry has leaves comprised of three leaflets and low growing, blue-green stems densely covered in small thorns. It has separate male and female plants and you can come across large patches that are all male plants devoid of fruit. First Nations used it for medicinal purposes as well as a foodstuff. The small berries are said to be even more delicious than the introduced varieties, although not so numerous and it is a parent of boysenberry, loganberry and youngberry. It is tolerant of many site conditions and was one of the plants that quickly re-established on Mt. St. Helens. It responds well to fire and logging and is an important winter browse for black-tailed deer. More than once it has jolted unwary hikers out of their reveries as the trailing stems seem to consciously reach out and trip the unsuspecting, bringing them down for a close view of one of nature’s valuable assistants.
References to Rubus ursinus from Plants of Coastal BC by A. McKinnon and J Pojar