Wild Buckwheat (Polygonum convolvulus)
by Jamie Puchinger
Wild buckwheat is an annual weed found on crop land throughout the southern prairies. It is resilient, persistent, relentless and tenacious plant despite control strategies. A single plant can produce 12,000 seeds in one growing season, but only 3% of the seeds germinate after reaching physiological maturity. Most of the plant’s seeds (97%) will germinate the following year but research indicates they can remain dormant for several years and germinate when conditions are right. Heat, cold, light and scarification affect seed dormancy length.
Cotyledons are narrow with a rounded tip and base. Plants have long, slender, creeping stems with alternate, heart or arrow-like leaves. Leaves have pointed tip and widely separated lobes at the base. Wild buckwheat blooms indeterminately (all stages from new buds to ripe seeds can be found on one plant) throughout the summer, but it lacks petals. Instead it has five whiteish-green sepals that tightly enclose a single seed. Seeds are dark brown to black, triangular shaped and about 1/8 inch long. Field bindweed can be confused because of the vine growth habit and arrow shaped leaves. Bindweed does not possess an ocrea, thin membrane around stem at each node, and has white or pink large, funnel-shaped flowers.
The vine-like weed starts creeping on the ground before it becomes entangled with the crop; which can cause lodging making harvesting difficult. Five plants per square meter (m2) may reduce wheat yields by 12% and 56 plants per m2 can reduce yield by 28%.
Cultural practices such as mowing, crop rotation, post-harvest cultivation, delayed seeding, can reduce wild buckwheat stands, but are not effective in control. Wild buckwheat is one of several weeds showing resistance to Group 2 chemicals on the Prairies. This means control requires multiple modes of action through tank mixes. The weed is tolerant to MCPA and moderately tolerant to 2, 4-D. Researchers say bromoxynil, clopyralid, dicamba, glufosinate and sulfonylurea products are the most effective wild buckwheat control.