Ground work: May is the time for sweat and toil in the garden but you'll reap the benefits all summer long

In a garden, timing counts. That doesn't mean clock-watching. It doesn't matter whether lettuce seed goes in at 11.23am or 4.26pm. It will still probably grow. But May is a kind of watershed in the garden. If you can guide the place in the right direction this month, then there should not be too many wobbles during the rest of the summer. If you lose this slot, then somehow you never catch up.

Even if the garden is no more than a place to sit with a glass of wine between Met Office weather fronts, the principle is the same. It's more relaxing to sit in surroundings that give pleasure. So, although I hate to see a garden reduced to a list of jobs, here are some ways to set up a stress-free summer in the garden:

1. Chuck. Call it editing, if you think it sounds less cruel. Every spring our eldest daughter does it with her clothes – wardrobe editing – and is terrifyingly ruthless. But look round your garden. There are probably plastic pots with nothing in them, pots with dead things in them, bundles of torn plastic netting that will never again keep a blackbird off a currant bush, bits of toys and tools that you once thought you would mend but now know you won't. Bin them. Or empty the pots, wash them and stack them out of sight. Pull up the canes and stakes marking the graveyards of dahlias that died in the winter. You do not need to be reminded of them. Tie the stakes/canes in bundles. They are easier to stack that way. Get rid of the bald tennis balls and punctured footballs that during your clean-up will emerge from behind the raspberry canes or the berberis. Take a long hard look at the greying fleece that may still be swathed around the head of your banana plant. Does this sight make your heart lift? Is there joy, redemption, delight invested in this thing? If not, think hard about the banana as well as the fleece in which it has been wrapped for so many long months.

2. Mow. Unless of course you have abandoned grass in favour of gravel or smashed slate. If you have something you think of as lawn, it needs to be looked after. Foot for foot, lawns need more maintenance than any other part of the garden, but it's true what they say. A stretch of green soothes the mind and gives whatever plants you have around it a cool, calm setting. I positively like daisies, speedwell and clover in lawns. Not plantains and not dandelions or docks. Their skirts are too wide. They smother too much grass. Cut them out quickly with a sharp knife. It's better than dosing the whole lawn with herbicide. If you stop them seeding, you will avoid a great deal of trouble in the future. Mow, but don't scalp. Your children will be doing more than enough scalping on their own. Don't set the mower blades lower than 20mm. Attend to the edges. Good edges give an immediate impression that here is a well-tended plot. The job is easier to do if your lawn is bounded by boards or metal strips. If not, edge anyway. You don't need special long-handled clippers. Ordinary shears will do the job. Where lawn butts straight on to a hard surface, you don't notice the wispy bits as much as you do when the lawn joins earth. Concentrate on those bits and keep them sharp.

3. Prune. Anything that has already flowered in the garden has already given you its best shot. Forsythia, in particular, has nothing left to say. Its leaves are boring. Its habit is stiff. It has no fruit. It has no autumn colour. Many shrubs flower better on new wood than they do on old (but remember, I said many, not all) and pruning encourages fresh new growth. Many shrubs are allowed to take up far more space in a garden than they deserve. So if you are looking at an early- flowering shrub such as forsythia that has elbowed itself into areas that would be much better given to the rose that's hoping to flower next month, get out a saw, long-handled loppers or secateurs. Good cutting tools are essential in a garden. Most of us use our secateurs to do jobs that would be more easily and comfortably achieved with loppers. If you have good cutting tools, you need very little actual strength to achieve your purpose. I use Felco secateurs as well as loppers and a saw made by a Swedish firm, Bahco.

If you are looking at a forsythia that is bare at the bottom, congested and tangled in the middle with new growth only at the top, you need to act. Typically, forsythia is a shrub that flowers on several stems springing from the base. The oldest stems are generally the thickest. If the shrub has not been tackled for some time, you could start by taking out the biggest stem entirely, cutting it as low to the ground as you can. This will be a job for a saw. With saws, you don't need to push too hard. If you do, the saw binds (it gets stuck in its groove). Think of the stem as butter and let the saw quietly motor its way through.

When that stem is cut and dragged out of the way, mark in your mind the stem that you will remove this time next year. And the year after that. Many shrubs that have got too big for their boots can be refreshed and renovated on this basis – a three-year cycle of removing all the really old stems to stimulate fresh growth.

Then take a look at the rest of the shrub. Some of the new growth will be springing out halfway up an existing branch. Cut back to the new growth. The stuff you are chucking will be the shoots that flowered this year. Do as much of that as you feel like. Then take at look at your wintersweet (Chimonanthus praecox) and your other early-spring-flowering shrubs and see if they, too, need drastic action. It's amazing how much bigger a garden can seem when shrubs are properly pruned and tied in, if necessary, to walls or supports.

4. Weed. I love weeding, though I don't expect others to bend to it with cries of joy. But if you weed now, you won't have so much to do later. Annual weeds grow at a fantastic pace this month. Some, like bittercress, may have already catapulted their seed cargo. Five thousand seeds per plant. At least. Argh! Don't race at weeding feeling it's all got to be done at once. Just get into the habit of pulling at least 10 every time you pass through the garden to do something else. While they are young, weeds come out easily. Concentrate first on the annual ones, to stop them seeding. Then keep a watch for the first juicy shoots of bindweed. Be ready with the spray bottle. It's one of the few occasions I reach for poison. If you catch it young, bindweed is not yet tangled with things you don't want to kill.

5. Mulch. I've written much in the past about the importance of mulching, and it's all true. It suppresses annual weeds, and as it breaks down it provides humus and trace elements for your plants to feast on. It also conserves moisture in the soil, but the moisture has to be there in the first place. Only mulch after a good downpour. Right. Enough! I'm off to fight the ground elder.