A native of Southeastern Europe. the bur buttercup (Ranunculus testiculaus) is an invader that is now common in several western states. It can be found in pastures, along roadsides, in waste areas and grain fields – disturbed areas. Bur buttercup is very competitive in drylands. These alien buttercups in the photographs are growing near the gate in one of our dryland pastures where our horses denude the ground (Modoc County CA) – perfect habitat.
An annual, bur buttercup is one of the first spring flowers, arriving right after the snow melts. Growing 2 to 5 inches tall, bur buttercups have grey-green leaves that are basally attached. The hairy leaf blades are divided into fingerlike segments. The flower has five yellow petals and develops into stiff brown burs that cling to fur and clothing like Velcro. The immature burs in the photographs are still green. The plants can grow singly but often form dense mats.
Bur buttercup is considered a noxious weed because it spreads rapidly and contaminates grain fields. The small burs/seeds are often difficult to separate from the grain seeds. Bur buttercups contain ranunculin which changes into protoanemonin when the plant is crushed. Protoanemonin is highly toxic to sheep.
Ceratocephalus (from the Greek meaning “hornhead”) is another genus name for bur buttercup. Common names for this early spring arrival also include testiculated buttercup, male buttercup, and curveseed butterwort.
The day I first noticed the bur buttercups in the pasture was rather dark and rainy. I took a few pictures then went back the following day to photograph the flowers in the sunshine. Much to my surprise, in just one day all the flowers developed into young burs and there were no more flowers to photograph. That was quick!