Spiny, yellow and on move
Buttercups are familiar wildflowers, typically favouring moist meadows, stream-banks, shorelines, grassy slopes and forest edges throughout B.C.
Their irritant qualities are probably the basis of the children’s game in which one child presses a buttercup to the sensitive skin just below the chin, “to see if you like butter.” The slight redness caused by such casual contact is supposed to indicate a butter lover.
Of the 28 buttercup species noted as occurring in our province, a handful of them are introduced, and one particular species caught the attention of Okanagan-Similkameen residents earlier this spring. I first noticed this invader about a decade ago, and it seems to be on the move.
Bur Buttercup is an annual herb, native to southeastern Europe. It also goes by the aliases curveseed butterwort, little bur, hornseed buttercup and testiculate buttercup.
This buttercup grows in dry, sandy areas and has become widespread in gardens, grain and alfalfa fields, pastures, disturbed clearings and along roadsides in several western states, including California, Oregon, Washington, Nevada, Idaho, Utah and Colorado.
Within the Southern Interior it is known to occur as far north as Kamloops. It is a winter annual that emerges in early spring, when temperatures climb into the 7 to 10 C range.
The plants are only about 10 centimetres tall, and the flowers are very tiny. Like other members of the buttercup family, each blossom usually has five bright yellow petals. The leaves are divided into finger-like segments, so that they resemble a bird’s foot.
At maturity, each blossom develops into a hard, spiny fruit, which is the “bur.” By early summer, it scatters its seed and the burs have turned from green to straw-colored to brown. When the bur dries out, the sharp spines will lodge in shoes, bare feet, animal pads, clothing and even bicycle tires. Be sure not to confuse this plant with puncturevine, a much larger, mat-forming summer annual with seedpods that will actually puncture bicycle tires. I will write more about puncturevine in a future article.
Bur buttercup contains ranunculin, as do some species of the genus Ranunculus (buttercup). This chemical changes into a toxic chemical when the plant is crushed. Sheep have been poisoned and have died in the western U.S. after ingesting above-ground plant material; consequently, this plant is considered highly toxic. About 500 grams of green plant can kill a 45-kilogram sheep.
As well, reports from Nevada indicate that this weed can cause significant agricultural losses and will outcompete native species. Millions of acres of sagebrush grass rangelands are currently infested in the state.
So where does this leave us? I guess it’s one more weed to add to our list, as it seems to have the potential to become much more widespread in our region.
Prevention, as always, is your No. 1 tool with this invader. Learn to identify plants and start monitoring early in the season. Plants can flower within three weeks of first leaf emergence, so you need to be diligently checking your property soon after snowmelt.
It is important to control bur buttercup before they produce flowers and seeds. Hoeing, pulling and digging can control this weed.
Fortunately, it does not compete well with grass, so consider seeding a competitive grass mix or in the case of agricultural fields, some type of cover crop, to assist with control.