Wilde side

Kim Wilde answers your gardening questions.

White foam has appeared on my plants. The affected part withers and dies. I’ve been wiping off the foam and trying to squash any possible culprits. What is it?
Cuckoo spit is the spittle-like foam that appears from May to July on many herbaceous plants, shrubs and annuals. This foam houses the sap-sucking insect, the froghopper, which seldom causes harm to mature plants, but can distort young growth. A sharp blast with the hose should be enough to thwart it. There is also a handful of systemic pesticides – including Provado Pest Free, and Rose Clear 2 – but be warned: these will penetrate the whole plant. If you use a pesticide, read the instructions and don’t use them on anything edible.

I am tired of the dull green plants in my north-facing window box. What colourful alternatives are there?
Dull green plants? Sir, I can assure you there is nothing dull about green. Plants that flourish in shade often have striking foliage. Try Hosta ‘Frances Williams’, or the glossy fronds of Asplenium scolopendrium ‘Crispum’, or Alchemilla mollis, and I think you will quickly revise your opinion of green. There’s no crime in craving a colour fix, though, and bulbs are a great source. The small, yellow Narcissus ‘Cedric Morris’ flowers from Christmas to March. For spring flowers, try Scilla siberica. But you can’t beat the humble Busy Lizzie for flowering all summer in the shade.

I am about to acquire a garden which has a high water table. Part of the year, the ground is wet-to-waterlogged. Apart from drainage, how can I improve the situation?
Waterlogged soil is saturated for part of the year, dry at other times. I recommend adding organic matter, such as well-rotted manure, in the autumn, to improve soil structure. Then build a simple ‘soak away’ to absorb surplus water. A soak away is a pit of at least one cubic metre, sited at the lowest point in the garden and filled with rubble. In terms of what you should grow, Cornus varieties are a pretty safe bet.

Send your queries for Kim Wilde to: Wilde Side, Guardian Weekend, 119 Farringdon Road, London EC1R 3ER (weekend@guardian.co.uk), giving details of aspect and soil type. We regret we cannot respond to all your questions individually.