Ranunculus ficaria (lesser celandine) is a perennial member of the buttercup family. A British native, it is widespread in woods, hedgerows and on thebanks of streams. It spreads mainly by tubercles (bulbils) that form in the leaf axils and rapidly colonise disturbed soil. Occasionally, lesser celandine produces viable seed too.
This plant usually appears above ground in late February and usually dies back after late April. Because of the short growing period, the plant may not be a problem in gardens - it can even provide colour at a time when the ground tends to look bare - but it can be a real menace in some situations.
Attempting to dig out the plants often assists their spread as, unless great care is taken, this operation will distribute the tubercles. Mulching the surface of the soil with a 4in (10cm) deep layer of organic material may smother the weed, but in some situations the only method of control is to use a weedkiller.
Remove all cultivated plants first and then use a glyphosate spray (such as Roundup or Tumbleweed). If the plants can't be moved, a foaming aerosol formulation (Advanced Glyphosate Spot Weeder for Beds & Borders) may be more accurate than a ready-to-use spray. In some mature shrub beds an application of dichlobenil (Casoron G4 Weed Barrier) in February or March will give satisfactory control. Repeat treatments may be necessary until all plants are dead.
Celandine in lawns is difficult to eradicate, as it is resistant to most lawn herbicides. An application of a selective lawn weedkiller based on MCPA (such as Evergreen Feed & Weed Liquid) may considerably check growth, but will almost certainly need a repeat treatment in the following spring. The first application should be given early in the season (as soon as the leaves are fully developed), followed by a second application three or four weeks later.
Leigh Hunt