Start planting outside but there's still danger of frost; We may have enjoyed a few days' warm weather, but don't get too carried away in the garden, says Roger Clarke.
You can plant out tomatoes in a cold greenhouse now using growing bags, large pots or bottomless pots. If the soil is in good condition you can also plant directly into the border. Bury a 3in pot to its rim at the side of each plant to assist in watering if you are planting in the soil.
Water well and feed when the first trusses appear.
Outdoor tomato varieties are much more reliable these days but are still not hardy so don't risk them until the end of the month.
On hot days greenhouses can become very hot and dry - conditions loved by red spider mites - so ventilate as much as possible and damp down on hot days. It sounds technical but just means drenching the paths and staging with water to cool the house down and to increase humidity. You can also leave a container of water, an old washing up bowl is ideal, to help keep humidity up.
Don't be in too big a hurry to plant out. The danger of frost has not yet gone so plants such as dahlias are best left until the last week of May. If cuttings taken earlier are becoming pot bound then pot them on. It is safer than risking them out in the garden.
Tubers can be planted now and any shoots which appear should be earthed up if there is a danger of frost.
Potatoes which are showing growth should be earthed up to protect from any frost. This has the double benefit of killing off weeds and also increasing the crop.
If you look at potato stems they are spiky and knobbly and when the shoots are covered with earth, new roots develop easily and at the end of each root should be a potato. The more roots from the stem the more potatoes.
Weeds are enjoying the warm spell so get to work with the hoe. Perennial weeds such as dandelion and dock are best dug out although regular hoeing will eventually kill them off. Couch grass is a perennial you cannot hoe to death. Each but of root becomes a new plant, so dig it out.
If couch grass or any invasive weed has become entangled with the roots of another plant or shrub then use a weed killer such as Roundup or Tumbleweed, or a spot weeder.
You can use a fine brush to paint the weed killer on to the weeds or, very effective, wear a rubber glove covered with a cheap, thin, cotton gardening glove and dip the thumb and finger into weed killer then grasp a weed shoot and pull your thumb and finger along it to coat the surface. You can use your other hand to move shoots of the wanted plant away. It avoids the risk of damaging the wanted plant and gives the weeds a fatal coating.
If you do accidentally get weed killer on a wanted plant then don't try to wash it off, which spreads it, but cut off the affected stem below the contamination before the hormones have the chance to spread through the plant.
Weeds do tell you a fair amount about your soil. If they are germinating rapidly then the soil is warming up nicely and you should have quick germination of the final sowings of hardy annuals and vegetables such as lettuce, carrots, radish and so on.
Don't go mad with salad crops. Sow a little and often so that you have a regular supply of lettuce, for example, with the rest of the crop in various stages of readiness. Sowing about 4ft of a row a week should produce about five or six lettuces a week later in the season.
It is also worthwhile trying turnips as a summer vegetable, sowing them fairly thinly almost like radishes. Pick them at golf ball size and they are sweet and delicious, nothing like the tough, root vegetables to bulk up winter stews.
Grass grows best on a slightly acid soil and in general if moss has been a problem then that indicates both the soil is acid - although some moss will grow on alkaline soil - and low of nutrients.
If clover is a problem then that indicates the soil is alkaline so a feed with an acid fertiliser will help to deter any reappearance after weeding and feeding. Water in about a quarter ounce of sulphate of ammonia to the square yard twice a month for a couple of months. It will also help to green up the grass.
Ideally you should know the acidity of the soil in you garden and lawn and simple test kits are available from garden centres including electronic probes which give an instant read out. Then you know what sort of plants and fertilisers are most suitable for your garden.
Arisaema sikokianum, a stunning cobra lily from the highlands of Japan
A lily with more than a little bit of bite in it
Gardeners are always looking for something different. That is what has driven plant hunters over the centuries, which in turn has provided us with a rich heritage of plants from every continent to choose from.
At a recent show I came across Viv Marsh from Walford Heath, Shrewsbury, who is both importing and breeding plants, many of which are rare and certainly not common in garden centres.
One of his imports is Arisaema sikokianum, a cobra lily. Most Ariseamas come from the Indian sub-continent, where cobras are common, but sikokianum also hails from the highlands of Japan where cobras are somewhat rare.
Cobra lilies enjoy warm wet summers in the wild where they grow in the mountains. Winters are cold but dry and that is the key to success in this county. They must be in well-drained soil otherwise the bulbs are likely to rot. They also hate full sun so need to be grown in shade.
Supplies of sikokianum are limited, hence the price of pounds 15 a bulb, and all the bulbs are from commercial nurseries and not pillaged from the wild. It grows to anything from 8-16 inches.
For more deetails, log onto www.PostalPlants.co.uk. The nursery is not open to the public because of planning regulations.
Forget-me-nots and honesty are the epitome of the cottage garden, but if you like formal gardens with plants staying where you put them, then beware.
Both are very hardy, very prolific and can quickly become weeds if they are allowed to seed. The forget-me-nots, Myosotis, came from half a dozen plants about three years ago and now pop up all around the garden each spring.
The honesty, Lunaria annua, a biennial, came from a couple of plants and seems to have taken over a dry, shaded bed as its own which is not too much of a problem as any seedlings which appear elsewhere can be moved to join the rest of the party.
If you grow honesty then make sure they are well away from the vegetable patch. They are members of the cruciferae family, the same as brassicas, and can suffer from the same diseases including club root and white blister.