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Expert advice on hydrangea blooms, stunted sunflowers and pruning wisteria
Q
Is it the right time to prune my wisteria and jasmine plants? DAISY FALLON, KIDDERMINSTER, WORCS
A
It’s just the right time to prune your wisteria. By now it will have produced long shoots and these should be cut back to just four leaves. Go over the whole plant, cutting back all the long stems except those you want to tie in to extend the reach of the plant. This will encourage the development of flowering spurs. However, don’t prune summer jasmine, which should be in flower now. It flowers on short shoots on old stems and any pruning will reduce flowering, so just a light pruning in spring, to tidy up the plant, is all that’s required.
Q
Can I prune an overgrown acer? DEBRA COLLINS, BY EMAIL
A
It’s easier to prune Japanese acers in summer because you can judge the exact shape, though this may cause sap bleeding, so it’s best done in winter. Avoid giving the tree an overall trim, which will spoil its shape. Instead, remove branches back to where they fork and thin out the crown first, all over, then shorten any offending branches.
Q
When should I prune an old spiraea? MARCIA HOLDEN, GREAT YARMOUTH
A
Spiraeas such as ‘Goldflame’ are grown mainly for foliage and should be pruned in spring. They flower on the new growth but if you lose a few flowers it’s no great loss. But spring-blooming white-flowered spiraeas need pruning straight after flowering. It’s too late now; just prune out about a quarter of the stems near the base so new growth has space to develop.