As the weather warms up, the grass will be growing - so you need to get rid of lumps, bumps and bald patches to ensure you have a carpet of green velvet in the months ahead.

A good-looking, healthy lawn not only makes the whole garden look tidy and provides a wonderful framework for colourful beds and borders, but it also helps encourage wildlife into the garden.

You should already have begun work on drainage and oxygenation, but it's still not too late to scarify the lawn with a springtine rake to remove thatch - dead grass that mats beneath growing grass - and moss. For larger lawns, it's worth renting a petrol driven lawn scarifier to do the same job.

If you have loads of moss, apply a moss killer before you scarify and wait a few days before raking it up, following instructions carefully.

Next, you need to improve badly draining soil by aerating the lawn, driving a garden fork into the ground all over the lawn when it is moist, making holes to a depth of 10-15cm (4-6in). I once bought a pair of lawn aerating shoes, but they were pretty cumbersome and kept falling off, so I went back to the fork.

Others use hollow-tine lawn aerators which remove plugs of soil from the ground, but they are hard work and aren't very good on stony soils or heavy, dry soils.

The holes you make allow air and water to get into the grass roots and should then be filled with a mixture of sharp sand and organic soil conditioner to stop the holes from closing up.

Feed the grass with lawn fertiliser available at most garden centres. This can be done by hand, applying approximately two grams per square metre, and water it in.

All lawns need good drainage and oxygenation, Some lawn dressings incorporate a slow-release fertiliser but if this isn't the case, add a little amount of general lawn fertiliser (not containing weed or moss killer) before applying it. Make sure you brush it evenly over the area or it will become patchy when the fertiliser kicks in.

A few weeks later, if your lawn is still patchy, oversow it lightly with a quality lawn seed.

Bumps in a lawn are a common problem. They'll be regularly scalped by the mower and tend to become bare. To correct this, you may need to cut the turf at the area of the bump with a spade or an edging iron, peeling back the turf carefully and removing or adding soil as necessary to level the turf.

If the bump is prominent, you may need to remove some subsoil and replace topsoil, treading down the disturbed soil before firming back down the rolled-back turf after checking that the area is level, and filling the cracks with sifted soil.

You may feel your lawn is beyond repair if it's weed and moss-ridden or full of bald patches. If two-thirds of the area is moss and weeds you may be better off starting again, turfing or seeding a new lawn.

But if you do decide that it's worth saving, first cut it with the blades set quite high. If your grass is already long, give it a few cuts over a number of weeks, lowering the blades a little at a time, so that you cut the grass length down gradually.

By summer, you should be mowing weekly, stepping up to twice a week when necessary, but don't mow the grass shorter than 2.5cm (1in) high and keep on top of weeds in the lawn. Annual weeds which emerge in any bare patches will be removed by mowing.

Feeding should continue monthly through the summer, and in the autumn a high-potash fertiliser should be applied to keep grass luxuriant over the winter.

In dry weather, leave the clippings to shower and cool the surface, or a mulching mower can be used, which chops the cuttings up very finely and forces them back into the lawn where they provide valuable nutrients and help to prevent the turf drying out.

If it becomes necessary to water the lawn, avoid evaporation by watering in the early morning, late evening or using a timer at night. And even if watering does have to stop completely for a while and the lawn goes brown, it will recover once the rain comes.

BEST OF THE BUNCH - Fritillaria meleagris

These beautiful bulbs, snakeshead fritillary, are native wildflowers that we have adapted into our own gardens, growing to around 30cm (12in), with nodding mauve or white heads with a checkerboard pattern, above lance-shaped greyish-green leaves. They look great in a wildflower meadow, or in a rock garden or raised bed. They do well in moist but well-drained soil in sun or partial shade. Plant the bulbs in autumn at four times their own depth.

GOOD ENOUGH TO EAT - Protecting salad crops

If you want to stop your prize lettuces being decimated by greenfly and blackfly, invest in some insect-proof mesh, available from specialist organic gardening supply firms. The mesh, which needs to cover your low-growing crops and be weighted down with bricks, not only screens out predatory insects but also keeps birds and cats at bay, but allows rain to pass straight through it and reduces evaporation by sheltering crops from wind, so the soil doesn't dry out so fast. It can also be used in summer as, unlike horticultural fleece which traps heat underneath, it won't cook your crops. Make sure you put it on as soon as you start sowing or you may just trap insects underneath it. Also, be aware it won't deter slugs and snails, which may creep in underneath, so you'll need to be vigilant. And if you are growing beans, peas and courgettes, which need pollination, you'll need to uncover them once they start flowering or the bees won't be able to access them.

WHAT TO DO THIS WEEK

:: Plant agapanthus bulbs in groups in large pots, or directly outside in warm, sheltered borders.

:: Move back containers of shrubs and permanent plantings from their sheltered winter homes to their usual positions.

:: Sow a short row of lettuce every other week to ensure a regular supply of leaves throughout summer.

:: Sow peas and mangetout outside.

:: Continue potting up rooted cuttings of chrysanthemums and plant out well-rooted plants once they have been hardened off in a cold frame.

:: Support growing border plants to stop them from collapsing in the wind.

:: Divide congested clumps of pampas grass.

:: Continue to water newly-planted trees until they are well established.

:: Cover stems of newly-emerging early potatoes with fleece to protect from frost.

:: Prepare trenches for planting out young celery plants raised under glass.