Country: The answer is blowing in the wind

Chemical sprays radically cut down on the labour of gardening - but they can also be treacherous friends.

Wherever more than one person gardens on the same piece of land, you will find the rumblings of a great weedkiller row. Everyone has had one, and years after the event you can still inadvertently stir up an ancient quarrel by an ill-judged comment. Wandering around a friend's garden recently, I made some inconsequential comment about a pair of Irish yews planted either side of an entrance. I could not help noticing that one was 3ft higher than the other.

"That's because he spilt the weedkiller," said my friend resentfully. Her husband's spill had been fatal to one of the pair and they had had to replant. The incident, already five years old, was still a red-hot issue as far as she was concerned. Time had not healed this rift.

All round the gardening world you hear the echoes of similar recriminations. Sodium chlorate has a lot to answer for ("but I swear I only put it on the drive - honestly"). All gardeners can recite lists longer than that of Beachcomber's cabdrivers, of particularly choice and beloved plants cut down in their prime by a careless swing of the watering-can ("but I didn't see it spill; I really didn't"). Only one thing is common to all tales of weedkiller woe. It is always the other person's fault.

Gardeners of an organic bent may now be feeling very smug and planning letters pointing out that there is no need to use weedkillers at all. In ideal circumstances, this is so. If you have as much time as you want to garden and if you start with a plot reasonably free of real thugs, such as bindweed, couchgrass and ground elder, you can, by mulching and hoeing, keep the place as weed-free as the Sahara Desert.

For five years, I made a conscientious effort to stick to these principles, but in an acre and a half of richly fertile garden, which had been abandoned for the previous 20 years, this was soon a losing battle. Every patch had to be won from a wilderness of briar, elder, nettle and dock and an army of lesser weeds.

When I went off to conquer new territory, the weeds quickly recolonised my oases of planting. Then I found glyphosate and, in the best Mills & Boon tradition, thought I would live happily ever after. Set against what is available, my herbicidal armoury is minute. I do not use weedkiller on lawns, in the vegetable garden, among fruit trees, or round flowers and shrubs. It is used on the drive, some paths and paving, but its primary use (in the early days) was for clearing ground before planting.

In the end, the only feasible way to retrieve our bank from the wilderness was to concentrate on a strip at a time. Each year, between March and September, I treated one strip with glyphosate (Monsanto's Roundup), spraying more than once where ground elder and bindweed were especially persistent. Only when the ground was absolutely clean did I plant it and move on to the next, adjoining strip to repeat the process. The whole thing took years.

I didn't dig the ground at all, but in the autumn planted among the corpses of docks and nettles. The aim was to plant each patch so thickly by spring, that weeds would have a hard time muscling back in. Once cleared and planted, each patch was mulched heavily in autumn or winter with mushroom compost, leaf mould, grass cuttings, whatever I could lay my hands on.

The secret of low-maintenance gardening (and I discovered it the hard way) is to start with absolutely clean ground. It is difficult to achieve this by digging. Roots of ground elder, couch and bindweed will all sprout from the tiniest morsel left in the ground. As these roots are brittle there are usually plenty of morsels hanging about like time-bombs, waiting to explode in spring.

Glyphosate is one of a group of weedkillers that are, in manufacturers' jargon, translocated and non-residual. Non-residual means that the weedkiller acts only on the weed and should not lurk about in the soil. Translocated herbicides are absorbed through the leaves of a plant and then pushed on down to the roots, killing the whole thing stone dead. Paraquat destroys only the green parts of a plant, so is more effective against annual than perennial weeds. Both are non-selective, which means that they will not be able to tell a dahlia from a dock.

Soil-acting weedkillers are more sinister, only to be used (and then only sparingly) in places where you do not want anything to grow ever again. These weedkillers are first absorbed by the roots of a plant, then sent up to kill the parts that are above ground.

The active ingredients hang around in the earth to stop fresh weed seeds germinating. Dichlo-benil (Casoron G4) and simazine (contained in Miracle's cocktail Pathclear) are both non-selective, persistent weedkillers to use on drives, paths or paving which you want to keep weed-free for ever. But would these areas not be prettier if flowers were allowed to self- seed in the cracks?

At low dosages, the manufacturers suggest, both these preparations can be used to control weeds among established trees and shrubs. I have not tried this, as under the system I have now adopted, I can easily keep up with the weeds. Some shrubs - choisya, forsythia, cotoneaster, prunus and viburnum among them - do not take kindly even to low doses of simazine. Senecio, gleditsia, larch, elder and symphoricarpos are allergic to dichlobenil.

Both dichlobenil and simazine are best used in late winter, when, in cold, moist soil, their effect will persist for months. Contact weedkillers such as glyphosate and paraquat are most effective in summer when weeds are growing full tilt, with maximum leaf area to receive the spray.

Glyphosate is especially lethal when weeds are flowering, and in late summer when roots are fat with stores for winter. Treat all weedkillers with caution.

Chemical giants such as Monsanto generally get such a bad press, that they are understandably bullish when it comes to defending their products.

A little while ago I wrote to Monsanto, asking for the most up-to-date research on the non-residual nature of glyphosate in the soil. I had used this weedkiller for several seasons to treat persistent weeds among some sheets of old daffodils. All the bulbs subsequently disappeared. I must have been using it while the daffodils' foliage was above ground, they replied. In August? They must be joking.