How do I control slender speedwell in my lawn without chemicals?
C Hill, Aylesbury
This common lawn weed has small pale-blue (or mauve) flowers in late spring and early summer, kidney-shaped leaves and low, creeping stems that root at intervals along their length, forming dense clumps. It is difficult to eradicate, but control measures include weeding by hand; feeding the lawn regularly, to keep the grass growing strongly; and raking over the slender speedwell before mowing. This raises loose stems off the ground so they will be severed by the blades. However, fragments scattered when mowing can develop roots, so place a grass box on the mower to collect the clippings.
Can you suggest some pink or lilac colchicums for my garden, and when should I plant them?
D Hanson, Tewkesbury
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Colchicum autumnale (naked ladies) is a perennial bulb with goblet-shaped lilac flowers (4in-6in tall) in September and October. These are followed by a display of strap-like leaves. You could also try Colchicum speciosum 'Water Lily', which has larger, multi-petalled pink flowers, and the magnificent 'The Giant'. Both are ideal for growing at the front of a border and naturalising in rough grass. Allow the leaves to die back naturally rather than mowing them. The bulbs should be planted (4in deep and 6in apart) in August or September and prefer a humus-rich, moist but welldrained soil in full sun, although Colchicum autumnale is quite happy in dappled shade. A wide range of colchicums can be ordered at www.avonbulbs.com.
Neil Wormald is a qualified horticulturalist.
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