THERE have been a number of panicky letters in my postbag recently. From gardeners waking up from their deep winter slumber to find that they can't buy unleaded petrol any more! They got out their old-fashioned mowers and were shocked to find that the local garage no longer sells leaded petrol or that new-fangled lead replacement petrol that was supposed to take its place.

Not to worry. You shouldn't have to buy a new mower; not just because of the petrol problem anyway. You may, however, have to have the mower serviced with some slight modification. The work entails a de-coke to the cylinder head and a change of spark plug so that the engine runs sweetly with lead-free petrol.

The sounds of the early lawnmowers have been heard all around the district in the last few weeks. If you're one of the odd ones out it's high time to get under way on the annual effort to produce a lawn that's as good as we can get.

In my garden the first steps were a couple of preliminary cuts to tackle the straggly winter growth. There's time to catch up at this stage, setting the mower blades at 50mm (or two inches if you prefer) to top the grass, and then repeating the process as necessary for the next couple of cuts. The blades can then start to come down, shortening the grass length by a centimetre at a time until summer is really here.

It is a mistake to cut the grass too short at the first mowing. A few trims, twice a week if necessary, will help the grass mat to thicken up whereas too severe a cut will only result in yellowing and put the programme back even further.

Mowing too close is one of the most common causes of trouble and especially so when we get a long dry spell.

Most lawns have moss in them this year and in my own case it's an annual problem that always seems worse than the previous year. A proprietary moss-killing treatment will do the trick, helped by fertiliser rich in nitrogen, and followed by a stiff raking ten days or a fortnight later when the moss will be dead and live spores won't be scattered far and wide. Pay strict attention to the instructions for using moss-killers, especially in the rate of dilution and dosage for liquid treatments and the need for watering in granular products where necessary should there be no rain within a day or so.

Feeding and weeding are the next jobs. Spring feeds will be high in nitrogen value to encourage leaf growth and greening and this is the time to tackle weeds. Most selective weedkillers are at their most effective when the weeds are in active growth. The best day will be calm and the grass should be on the dry side although with moist soil underneath.

I like to tackle the big weeds, daisies, plantains, dandelions and the like, getting down on my knees with a sharp knife to dig out the offenders.

There will be some bald batches to deal with as a result. Some will be reseeded but others will be filled with a few of my home-grown transplants. It's a simple matter of filling a multi-celled seed tray with compost, sprinkled on top with lawn grass seed producing almost 200 plugs to fit exactly into holes made by a home-made dibber cut to the same shape.

The plugs are trimmed with a pair of scissors and used for instant repairs on those patches of lawn worn bare by frequent use in gateways, near paths, washing lines, and the like. It's a bit like a hair transplant