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The Most Wicked Weed of All
by Carla Allen
by Carla Allen

Greetings from Nova Scotia!

Carla Allen has been gardening for the past 25 years, co-owned a nursery in southwestern Nova Scotia for 16 years.

Carla has an extensive image library and nurtures a network of horticulture in the region. She was the first president of the Yarmouth Garden Club.

June 18, 2006

With a heading like that, how many of you are wondering if I’m going to be highlighting the weed that gives YOU the most grief? If you had a plant on your property that grew 3-4 metres tall and reached out to grab you and sink inch long thorns into your flesh every time you passed by, wouldn’t you call it the most wicked weed of all?

Locals here call this nasty ‘briers’ or ‘pickers’. Some call them brambles. However the scientific name for them is Rubus. Rubus, also known as blackberry, is a very large family that includes the ‘good’ blackberry that produces the luscious fruit we harvest in late summer.

We have several varieties on our property and I’m willing to tolerate those that produce fruit. The problem is, Rubus is extremely variable and has sometimes been divided into many species and varieties. There is also considerable genetic variability in this species with respect to leaf shape and fruiting capabilities. Therein lies the problem. There are many arching, entangling, woody, stems armed with savage backward pointing thorns...that seemingly never produce any fruit. They’re simply waiting to struggle with me when I arrive to root them out of the ground.

Stems of Rubus can root at the tips to form new plants. When this happens, the new plant separates from the old when it begins to die. New stems grow from the base each year. It also has branched, creeping underground roots. After four years, seeds are produced. These may be eaten by birds and are then widely dispersed to germinate readily.

In New Zealand, the spines of Rubus varieties have been known to trap woolly sheep. One way farmers help to control the weed in that country is by letting goats graze upon it.

Blackberries tend to form dense thickets and stems can grow up to 5m from a perennial wood crown, and live for 2 to 3 years, when they are replaced by new stems. Up to 70% of a thicket may consist of dead stems.

To date, the most satisfying method of control for me has been to pull these suckers out by their roots. They don’t tend to grow back once you’ve cleared the area and then it’s just a matter of removing any small ones sown by birds. It’s important to wear heavy gloves and long sleeves for this job.

Natural Resources Canada reports that Rubus species, namely R. strigosus (syn. R. idaeus var R. strigosus), R. parviflorus, and R. spectabilis, are among the top 20 forest weeds in Canada. The reason being, they effectively compete with young conifers in reforestation sites, reducing conifer growth and survival.

Research is being conducted into a biological control strategy for management of these Rubus spp. It’s a better alternative to chemical and manual treatments. A potential biocontrol agent Fusarium avenaceum has shown promise.


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