Creeping Buttercup

Perennial spreading by seed and long branching stolons or runners which root at nodes along their length, forming new plants; one plant can spread over a 4m² area in a year. The seed can remain in the soil for many years and germinate after cultivation. This is usually about 5 to 7 years, viability reduces to about 50% after 20 years, but viable seed have been recovered after up to 80 years (it is easy to believe the latter figure!).
A problem in lawns as it forms a rosette with the growing point at soil level, so it resists mowing and can also tolerate a great deal of trampling. Plants buried during cultivation soon regrow from great depths and re-establish on the surface, but repeated disturbance in hot weather will reduce the numbers.
Grazing animals can suffer from pain and inflammation leading to diarrhoea caused by a toxin in the fresh plant, but it becomes denatured in dry material so is not a problem in fodder. It is thought to deplete Potassium in the soil, so having a detrimental effect on surrounding plants (allelopathic). The leaves have three leaflets, each of which is lobed and as they mature they develop paler patches. This helps to distinguish them from similar looking leaves of ornamental plants such as Hardy Geraniums. The centre leaflet has a short stalk.
The bright yellow flowers have five shiny petals and occur singly on a grooved stalk from May to August. Fowering and seeding are more prevelant in dry conditions, in wet conditions the stolons are more plentiful.
Often the white, waxy mass of Root Aphids can be found at the base of the plants, but they don't seem to do much damage.

Height - up to 30 cm on open ground.

Dig out, clearing all of the runners; the white, fibrous adventitious roots do not regrow, but ensure that the growing point is removed. Cutting at an angle under the rosette will sever the tenacious roots and it is easily removed. Rake up the creeping stems before mowing so that they can be cut and so reduce its spread. They prefer the moist conditions of clay soils, so improving drainage. The numbers and prolonged viability of the seeds mean that total eradication is difficult, especially in cultivated ground.
Weedkillers to use:-
Glyphosate, systemic action killing the whole plant. Apply as spot weeder in the lawn. Treat the whole lawn with a selective weedkiller on its own ( eg. Verdone Extra) or a weed-and-feed type, it will probably take many applications to eradicate it because of the reservoir of seed and more mature plants may recover. Provided the soil is not disturbed the seed near the surface should eventually be eradicated.

See also Meadow Buttercup which is similar.

Follow these links for further details on Weeds, Weed Removal and Weed Prevention.