Identifying ButtercupsButtercups are both perennial and annual, and comprise about 400 species globally. The finely-palmate, alternate leaves are quite attractive, often with light mottling on the dark green. The flowers have 5 or more petals, and grow on long, hairy stalks; they are usually bright yellow and shiny, although some white is documented which is related to fading with age. Most Buttercups spread by seed, but Creeping Buttercup spreads by stems which root at the nodes. Once this plant establishes itself in your landscape, it is very difficult to eradicate and, because of the creeping habit, it can quickly crowd out all other plants. In some instances, this plant can be used on steep banks or areas prone to erosion, but be sure to use it only in areas well away from controlled landscaping.
ToxicityAll buttercups are toxic to varying degrees; the offending substance is protoanemonin. In humans, buttercup sap can irritate skin and mucous membranes; however, it has been used as a natural remedy for wart removal. Livestock are especially susceptible to buttercup poisoning from grazing, with cows being the most often poisoned. A cow with buttercup poisoning will give less milk, which will be bitter and tinted pink. In severe cases, colic can progress into respiratory distress and convulsions. Horses, sheep, and pigs are also prone to poisoning, but not to as great a degree. Dried buttercups are not poisonous, so if this plant is harvested with hay, it does not post a problem.
Because of its seeding and creeping methods of reproduction, buttercup is extremely difficult to control in field and pasture environments. In the home landscape, the problem is magnified because the use of herbicides (whether chemical or natural) is difficult to direct only to the offending weed. Systemic herbicides travel into the roots of the plant which, if firmly entrenched in a flower bed, are crossing and touching the roots of the desirable species. Transference causes poisoning of both the good and the bad. Topical herbicides such as vinegar are less disastrous, but harder to concentrate on the masses of leaves intertwined with adjacent desirable plants.
Oregon State University recommends removal of creeping buttercup in pastures by close mowing or by tilling up the ground and removing all vestiges of the plant. This must be done several times, but even then, remaining seeds can germinate into new plants the following season. Tilling or mowing our gardens isn't a reasonable option unless we are starting from scratch. So what to do?
Unfortunately, the best you can do is hand-pull the plants, preferably before they set seed. Be aware that any small pieces of the roots that are left behind in the soil will regenerate into new plants. If you have only a small patch of creeping buttercup, you might be able to kill it with vinegar before it spreads. To do this in an area where other plants are growing, use a spray guard such as the one in "How to Spray Weeds and Insects Without Killing Everything Else."
Other Ranunculus Species (partial)Alpine buttercup Ranunculus eschscholtzii
Bristly buttercup Ranunculus hispidus
Bulbous buttercup Ranunculus bulbosus
Bur buttercup Ranunculus testiculatus
California buttercup Ranunculus californicus
Celery-leaved buttercup Ranunculus sceleratus
Common water crowfoot Ranunculus aquatilis
Corn buttercup Ranunculus arvensis
Glacier buttercup Ranunculus glacialis
Goldilocks buttercup Ranunculus auricomus
Greater spearwort Ranunculus lingua
Lapland buttercup Ranunculus lapponicus
Large white buttercup Ranunculus platanifolius
Lesser celandine Ranunculus ficaria
Lesser spearwort Ranunculus flammula
Marsh buttercup Ranunculus cymbalaria
Meadow buttercup Ranunculus acris
Mount Cook Lily Ranunculus lyallii
Persian buttercup Ranunculus asiaticus
Pond water crowfoot Ranunculus peltatus
Pygmy buttercup Ranunculus pygmaeus
River water crowfoot Ranunculus fluitans
Sagebrush buttercup Ranunculus glaberrimus
Sardinian buttercup Ranunculus sardous
Swamp buttercup Ranunculus septentrionalis
Thora buttercup Ranunculus thora
Utah buttercup Ranunculus jovis
Water buttercup Ranunculus longirostris
Western buttercup Ranunculus occidentalis
Photo: sannse, with permission GNU FDL Wikimedia
Veterinary Medicine Library, University of Illinois
Oregon State University Extension
Montana Plant Life onlinePlantFiles