I have some sort of berberis that has been decimated by caterpillars. They are white and yellow, with lots of tiny black dots. What can I do?
You've probably got one of the following berberis: B. Vulgaris (an upright shrub that can be grown as a hedge and is the most demanding kind), B. Prattii (a dense shrub, rather thorny, with yellow flowers and an abundance of salmon pink fruit) or B.Pruinosa (another upright shrub that grows up to 8ft tall, with lemon flowers in spring).
The hungry caterpillar sounds as if it belongs to the magpie moth, which is attracted to various garden shrubs. Since you've already been invaded, it's too late to spray them - you'll have to wait for the caterpillars to turn into moths, then let the plant recover. It will do this on its own, but you can help it by keeping it well watered and adding fertiliser. When it has made a recovery, watch for signs of new infestation, at which point spray with a non-toxic spray containing a pyrethrum base; if you don't like using sprays, remove the caterpillars by hand.
Try to encourage more birds into your garden, to act as caterpillar predators - put out bird food and fix nesting boxes to nearby trees. In time, they will discover the extra food crawling over your beloved plants.
I have a sunny windowbox that I'd like to plant with things that aren't too twee but bring a little colour to my kitchen. Any ideas?
I'd suggest geraniums: they come in a range of beautiful colours and don't need watering that frequently. Add gazanias and trailing lobelias. Or, since it's a kitchen window, how about some herbs? Thyme, tarragon, marjoram and chives all have flowers, they smell really good and are handy for cooking. It's important to remember drainage, as waterlogging is often a problem in windowboxes. Before planting, place some river stones at the base of the container, and top it up with potting soil. Place the whole box on a drip tray and sit it on a piece of garden felt: this keeps light moisture around the roots and means less frequent watering.
· Send your queries for Linford Christie to: Guardian Weekend, 119 Farringdon Road, London EC1R 3ER (email@example.com), giving details of aspect and soil type. We regret that we cannot respond to all of your questions individually. Kim Wilde is away.