A problem shared.

Byline: By Peter Surridge

How does the tree in your garden grow? Peter Surridge has the answer.

Garden trees are growing in popularity ( the smaller kinds, understandably, to fit modern, small gardens.

Flowering cherries, hawthorns and rowans are among the favourites because of their dual display of beautiful blossom in spring and colourful berries in autumn. But they are not without their problems, as these queries from readers show.

Q: We have a rowan tree which is 8m (25ft) tall, produces plentiful red berries and has attractive sweeping branches. However, it will soon be too large for its position. I have always seen rowan trees in an oval shape. Could we cut our tree back without losing it?

A: The natural shape of the rowan varies. Some are fairly upright while others, like yours, spread their branches. Moderate pruning will not kill the tree but will promote growth, creating an unnatural, bushy shape. A better alternative would be to remove any branches that are too low and, if necessary, thin others, leaving some branches at full length. Do this work within the next month.

Q: My flowering cherry tree, now some 14 years old, developed splits in the bark last autumn ( splits that penetrated through to the wood of the trunk. The bark was also peeling off, revealing discoloured and very damp wood underneath. Is the tree dying, should I cut it down and would it be safe to shred the smaller branches to use as a mulch?

A: A fungal infection has almost certainly attacked your tree. The tree should be felled and burned, not used for mulch, for fear of spreading the infection. Do not plant another tree near the spot.

Q: I found a self-sown hawthorn seedling at the back of a border a few years ago and planted it in the lawn. It has grown about 2m (6ft 6in) tall but has only a few flowers and berries. Can I persuade it to produce more?

A: Hawthorns ( and some other plants ( grown from seed vary enormously in quality. In the countryside you can see some hawthorn bushes smothered in blossoms and then berries while others have very few flowers and fruits. For a reliably good display it is best to buy a named variety ( there are red-flowered forms as well as white. An alternative is to take cuttings from a bush known to flower freely, though it is against the law to take cuttings from the wild.

Q: Help! My garden is being overrun by ivy. Is it harmful to trees and brick walls? The birds love it and I would like to keep as much as possible.

A: Generally, ivy is not harmful and, as a native plant, it provides food, shelter and nesting sites for birds, butterflies and other creatures. Ivy growing up a tree will not normally cause a problem but if it grows into the upper branches and shades the foliage, it can contribute to the tree's lack of vigour or death. Cutting through the stems near the base will kill the ivy (leaving unsightly dead stems and foliage on the tree), though new shoots are likely to grow. When ivy attaches to mortar in a wall, not much harm is normally done, but removing the ivy can cause mortar to be pulled away at the same time.

Other recent queries have ranged from the windowsill to the vegetable plota

Q: Is there any treatment to combat cabbage root fly? Obviously growers who supply shops must use pesticides. I have tried placing carpet squares round the base of the stems and also wrapping the stems in silver paper.

A: Chemical preparations to control cabbage root fly are no longer available to amateur gardeners but only to commercial growers. I combat the problem with a combination of two methods which give me 90 per cent success. I sow seeds in my greenhouse in special growing cells called Rootrainers, available by mail order from Ronaash on [phone], so that the plants are able to grow to a reasonable size before planting out. I also sow more than enough to provide replacements. Then I plant out under fleece Easy Tunnels which allow light and moisture through while excluding pests ( or at least some of them ( until the plants are well established. These are available from Haxnicks [phone].

Q: When I moved to a new house with a neglected garden, it appeared to contain a weed from hell that I have identified as winter heliotrope. The weeds seem able to grow through or under a stone wall. Even after I cleared the area, it seemed to sprout again from every tiny piece of root. How can I eradicate this pest?

A: Winter heliotrope, Petasites fragrans, introduced from the Mediterranean, is deeply rooted and persistent. If you are planning to grow annual flowers or vegetables in the bed, dig out as many roots as possible before planting, then remove all you can find of the remaining roots after clearing the plot each autumn. I have used this technique successfully with such horrors as couch grass and ground elder. Otherwise, apply a weed killer containing glyphosate in early spring and again if fresh leaves grow, when they have reached a fairly large size. But keep some petasites ( what other herbaceous plant gives you purple, beautifully scented flowers in the depths of winter?