| Walla
Walla County Noxious Weed Control Board
Weed
of the Month
Buffalobur
Buffalobur, also called
Kansas thistle, is widely distributed in the West and native to
the U.S. but not to Washington State. This prickly annual of the
Nightshade family contains an alkaloid that can poison horses, sheep,
goats, and cattle. It can be a contaminant of garden seeds and birdseed,
so occasionally is found growing in gardens or under bird feeders.
Buffalobur may be an
erect or spreading plant up to 2 feet tall with a fibrous tap root.
Leaves are 2 to 5 inches long with deep lobes, prominent veins on
the underside, and are covered with spines up to ½ inch long.
Yellow, 1-inch wide, 5-lobed flowers appear in early summer and
develop into a spiny seed capsule containing many small black, wrinkled
and flattened seeds.
Buffalobur will grow
on most soil types and is often found in disturbed areas. It is
drought resistant and serves as a host for the Colorado potato beetle.
A single plant can produce 8500 seeds and since buffalobur can self-fertilize,
a single plant can start an infestation. Dry plants break off at
the soil surface in autumn and tumble to spread seeds. Seeds are
also spread by passing animals when the burs catch in their hair.
Control: For small infestations
or scattered plants, digging, hoeing, or pulling the plants before
blossoms appear is effective. Frequent mowing can prevent seed production,
if done before seedpods form.
Products containing glyphosate,
clopyralid, or picloram are reported to control this plant, although
data are lacking in the Pacific Northwest. Picloram is a “restricted
use” product and can only be applied by a licensed applicator.
Be sure to follow label instructions and precautions.
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