– Prune back last year’s long wands on wisteria to two to three buds. Pull off suckers at or close to the base.
– Large-flowered clematis are ready to sprout, so get them pruned. Remember, those that flower in May and September, such as ‘Nelly Moser’, only need tidying up and any dead stems removed. Those which flower only in September, such as ‘Jackmanii’, can be cut down to 18in (45cm). Both kinds are hungry plants and deserve a bucketful of rich compost each.
– To offset the flowers, cut the old leaves off hybrid hellebores, especially those clumps showing signs of leaf spot. By summer they will have withered anyway.
– Plants that are chopped back hard every year (red-stemmed dogwoods, buddleia, etc) want a generous dressing of old compost and/or a dressing of general, slow-acting fertiliser.
Readers’ queries
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Having stored my dahlia tubers in a cardboard box of fairly damp compost, I opened it recently to find the plants looking like rainforest undergrowth. Should I strip this early growth or buy afresh? R.F. Seymour, Derby
Oh dear. You stored the tubers too moist and let them get too warm too soon. The poor things decided to grow in the dark, like forced rhubarb. You were lucky the box was not a mass of mould inside. They should be kept dry and cool somewhere airy.
Clearly those dark-raised stems will not stand up for themselves and, if you snap them off at the base, where they join the tuber, it could take an age for new buds to be made and flowering would be late. I’d pot up the tubers and cut the stems down to the lowest pair of buds, keeping them cold and barely moist. In due course, two new shoots per old stem will appear – thin these out by breaking off the weakest one. Grow the plants on somewhere frost-free and in as much light as possible, and plant them out in May.
I have recently given my son and his family five young walnut trees. They’d planned to put them in the same pasture as the 20 apple trees that they planted last year, but we’ve recently been told that walnuts affect the growth and productivity of apples. If this is the case, what is the minimum recommended distance from each other? H. Taylor, Aspley Guise
Walnuts do discourage plants from growing under their canopy, by the production of the chemical juglone, but it’s only the American walnut Juglans nigra that is a real problem (especially to apples, tomatoes and rhododendrons). Our English walnut, Juglans regia, is far less toxic.
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Fortunately, walnuts are deep-rooting, so shallow-rooted plants fare not too badly under their canopy. I could take you to an English walnut today around whose trunk grows the best display of winter aconites and hardy cyclamen I have ever seen.
Juglone is transmitted mainly through root contact, sometimes causing dramatic wilting. If you plant your decent, law-abiding English walnuts at least a mature walnut’s height from the apples, then you should not go wrong, now or in the future. Juglone, by the way, is harmless to humans.