Country and Garden: The roots of life

There's nothing more satisfying than creating a whole plant from a mere twig. But you'll need patience.

THERE IS a moment in late August, particularly if you have not been away on holiday, when you discover that there is nothing very pressing to do in the garden.

Any lull is temporary, let me reassure you; the moment September hits her stride there are bulbs to be planted, perennials to be divided, lawns to be renovated and a host of other agreeable, time-consuming occupations to get on with. But, just this minute, nothing - apart from picking runner beans - seems that important. If you find this makes you uncomfortable, even edgy, you could always spend an hour propagating a few shrubs by taking "semi-hardwood" cuttings.

Most gardeners enjoy a spot of vegetative propagation. The average plant's inherent willingness to reproduce itself identically, from small stem stumps which grow roots, is one of the marvels of the natural world, made commonplace only by our familiarity with it. And it is, in most instances, pretty easy.

The time of year governs what kind of plant material we use, and how we treat it. In spring, cuttings are called "softwood", in summer "greenwood", by this time "semi-ripe", and in autumn "hardwood". These adjectives describe the relative bendiness (to use a non-horticultural, but useful term) of the shoot that is to be used as a cutting.

"Softwood" cuttings are taken from shoots only just grown and still lush and soft. "Semi-ripe" shoots, on the other hand, have firmed up during the summer at the base but are still quite soft at their tips. By the time the whole shoot has become woody, in autumn, they have turned to "ripe" or, more usually, "hardwood". It is all highly logical.

One virtue of of "semi-ripe" cuttings is that there is no very precise moment when they have to be taken; any time between mid-summer and mid- autumn, depending on the maturity of the shoots, will do. The method also works for a large range of deciduous and evergreen trees and shrubs. These include Mediterranean shrubs, such as lavender and rosemary, which are best replaced every few years; those shrubs, such as pittosporum, ceanothus, carpenteria, azara and leptospermum, which are hardy only in mild winters, and for which we would like the odd young plant as an insurance policy; hardy shrubs, such as box, escallonia, griselinia, berberis and cotoneaster, if needed in some quantity for hedging; a wide range of conifers; and even, if you are patient, those precious, expensive-to-buy shrubs, such as Magnolia grandiflora and Garrya elliptica `James Roof', which can be begged as cuttings from a friend.

Most of these cuttings benefit from being taken "with a heel", that is, pulled away from the main stem with a bit of that stem still attached. Cuttings with heels should be about 3in long, those cut below a leaf joint 4-6in. Trim the end of the heel (the "tail") with a sharp knife, and if the leaf area is substantial, cut it by half. Dunk the trimmed end of the cutting carefully in hormone rooting powder, preferably one with a fungicide in it. It is best to tap the cutting against the powder's lid, because too much powder up the stem will in fact inhibit rooting. Then, using a pencil or dibber, insert the cutting, to half its length, in cuttings compost (half and half, by volume, of peat or peat substitute, and perlite or sharp horticultural sand). Firm gently and water in. Pots and trays can be put in a closed "cold frame" (ventilated on hot days) or on to a north-facing window-sill but, in the latter case, the pot should be covered in a polythene bag, voluminous enough not to touch the leaves, and secured with an elastic band. This is to help maintain high humidity, until the cutting has rooted. Slightly tender shrubs, such as azara and Magnolia grandiflora, are best rooted in an electric, window-sill propagator (available from garden centres and DIY stores), which provides what is known as "bottom heat".

There is one drawback of this method of increasing shrubs. Cuttings may take many weeks to root and, even when they have done so, cannot be sent out into the hurly-burly of the garden border until they are of a size when they can hold their own. Once they have rooted, usually next spring, they should be put into a bigger pot of multi-purpose compost for at least a year, or planted out in a spare piece of garden in what is called a nursery row, where they can easily be kept weed-free. As you see, this is not an occupation for the impatient, but for the avid gardener who is always on the lookout for something constructive and interesting to do. And there is absolutely nothing wrong with that.