Q Why does my potted corkscrew willow lose leaves and suffer dieback?
A ANNE SAYS Corkscrew willows ( Salix babylonica ‘Tortuosa’) make dramatic winter outlines when the twisted stems are revealed. They are great for flower arranging and providing supports for spring bulbs in pots. Although willows like water, you should avoid planting a small rootball into a large container, where it will be swamped by wet compost, stopping oxygen reaching the roots. Conversely, I hope the roots were not allowed to dry out or overheat, which can happen when they are pot-bound. Whether or not the plant was well kept, the culprit could be willow sawfly larvae. These look like caterpillars, eat hungrily in large numbers and can defoliate their host plant. Keep a regular look out for them from spring onwards. If you see the larvae, put a sheet under the tree and knock it sharply so they fall onto the ground when you disturb them, then dispose of them.