Gardening: Sow much better

Growing flowers from seed can be far more rewarding than buying them off the shelf. Sarah Raven explains how to sow now for a summer full of colour - or you could always cheat and buy seedlings

GARDENING is like the fashion business: you have to think six months ahead, summer in winter, autumn in spring. Now is the time to think of sowing half-hardy annuals, which will give you intensely flowery areas from mid-summer onwards.

I have just been sowing my first packet of seeds this year - snapdragons. Antirrhinum 'Night and Day', a lovely high-summer plant with white throats to the flowers and rich crimson-black heads. The petals have a velvety texture, too. Snapdragons live for several years in Africa, where they grow wild, but here they are best grown as half-hardy annuals. Annuals live for one year only. They germinate, grow, flower, produce seed, and die in the space of eight months. Half-hardy means they can't withstand any frost.

Now and any time in the next six weeks is the perfect time to sow. Any earlier, and your seedlings have to struggle to survive weak sunlight and short days. The plants will be scrawny, etiolated things that will remain weedy and prone to disease. And if you sow later than the middle of April your plants will do well but will not be in bloom until August - just when your flowers are likely to be at their prime and you will miss a month or six weeks of flowering.

Aim to sow soon then, six weeks before your last frost; this is usually the beginning of May in London, a couple of weeks after that where I live in Sussex; and a couple of weeks after that in the north of England.

If you leave it a few weeks, you can cheat anyway, and buy seedlings of half-hardy annuals. Try Nicotiana alata 'Lime Green' and 'Deep Red' and the more ordinary Antirrhinums such as 'White Wonder'.

A general rule with any flower is to go for a single colour rather than a crazy jam-boree. It will have far more impact than a fussy, pointillist dotting of this and that. Choose four or five of the more unusual varieties: huge plants like the 6-ft tobacco plant Nicotiana tabacum, with leaves the size of tea trays, or Tithonia rotundifolia 'Torch', which will turn your garden into an orange-splashed jungle.

Grow tobaccos such as Nicotiana alata 'Deep Red' for their scent, the impressive 4-ft Nicotiana sylvestris for height; or to pick for the house try the elegant spikes of the American spider flower Cleome spinosa in deep pink, purple or white or Amaranthus caudatus 'Viridis', with its swags of velvety tassels.

You will need a 75-litre bag of multi-purpose potting compost. Choose a cheap mix, because the plants won't be in their pots for long and don't need anything richer. Allow one seed tray per packet of seed, and avoid cheap, flimsy ones that will buckle if you carry them in one hand.

Fill each tray with compost, sieving it if it is lumpy. Give the compost a good soaking and allow it to drain. Sow your seeds, always placing them individually where it is physically possible. This prevents two seeds germinating in the same pot and cramping each other. Some minute seeds, such as Nicotiana, are too small to separate by hand. Mixing them with a few pinches of a fine, dry sand makes them easier to sow.

Cover with about a quarter of an inch of sieved compost, then stretch a layer of clingfilm over the tray and cover that with newspaper. The clingfilm helps to retain moisture and the paper cuts out light and insulates the seeds. Most seeds germinate quicker in the dark (except for Cleome, so no newspaper with Cleome).

Place your trays on a well-lit - but not baking-hot - window ledge that doesn't have a radiator immediately below it. Choose a room that you spend a lot of time in so you will remember to water and check for signs of germination every day. If you have a propagator or greenhouse, use that, making sure that the plants are kept frost-free.

After about a week, when you begin to see the first seedlings appear, remove the newspaper and clingfilm. Transfer the trays to a cool place with plenty of light to encourage good roots to form before the upper plant develops.

Water so that the compost is moist but not sopping wet. In two or three weeks' time your plants will need to be "pricked out" (transplanted into individual pots).

If you don't have a garden centre nearby, phone for one of many seed catalogues available. Thompson and Morgan's is illustrated, which is very useful if you don't have a plant encyclopedia either.

Thompson and Morgan, Poplar Lane, Ipswich, Suffolk IP8 3BU, 01473 688588, fax 01473 680199; Chiltern Seeds, Bortree Stile, Ulverston, Cumbria, LA12 7PB, 01229 581 137, fax 01229 584 549; Sarah Raven's Cutting Garden, Perch Hill Farm, Brightling, Robertsbridge, East Sussex TN32 5HP, 01424 838 181, fax 01424 838 571, e-mail Ravenflora@aol.com

This week

1 Now is a good time to plant a tree, shrub or hedge. Dig a large hole, at least twice the size of the root ball of the plant. Empty five or six forkfuls of compost and/or well-rotted manure into the hole and mix it in. Place the root ball on top, keeping the top of the soil around the stem of the plant level with the ground. Replace the soil all around it in three stages, pressing the soil down around the roots each time. Then water it with a hose pipe for about an hour

1 Order a dahlia catalogue from Aylett Nurseries, North Orbital Road, London Colney, St Albans, Herts AL2 1DH, 01727 822 255 or from Halls of Heddon, West Heddon Nursery Centre, Heddon on the Wall, Newcastle upon Tyne NE15 0JS, 01661 852445

1 Plant snowdrops and aconites ('Eranthis') 'in the green' when they have finished flowering, but when they still have bright, healthy leaves. Persuade a friend with some in their garden to let you dig up a clump and replant them in your garden straight away

1 If you're looking for a good plant guide, the 'RHS A-Z Encyclopedia of Garden Plants' (Dorling Kindersley, pounds 55) is the most comprehensive