Red sails of summer; gardening

Biennials such as poppies, sweet Williams and foxgloves should be sown now for brilliant drifts of colour in next year's borders. And, warns Sarah Raven, timing is important: sow too early or too late, and you could be disappointed

PEOPLE THINK I've put fake flowers in the garden when they walk past the Iceland poppy, Papaver nudicaule 'Red Sail'. You can see them thinking, "That's not real. It can't be". Then they see the whirling plastic flowers next to them that look a bit like the windmills you buy at fairs and get really confused. I have scattered these around the garden to keep the moles away - they hate the vibration when they turn in the wind.

The flowers of this variety of poppy are big (two to three inches across) on top of a tall, narrow stem, two feet high. The petals are brilliant scarlet-orange, the colour of Heinz tomato soup, and though the flowers look far too delicate to withstand any wind or rain, they do. That is the wonderful thing about these flowers - they look vulnerable and fleeting, but are as robust and long-lasting as the next.

Poppies are biennials; plants that form roots and leaves in their first season, but don't flower until their second. Most biennials then set seed and die. They are best grown from seed sown any time from now until the middle of July. Sow them earlier, with your half-hardy annuals, and they will try to flower in their first year. This will weaken the plant and they won't be nearly as good next year. Sow them later, and the plants won't be substantial enough to put out in the garden in September.

The ideal scenario is to sow them inside now, but aim to get them into their final flowering position when there is still warmth in the soil and long hours of daylight. They will then establish themselves quickly, forming decent plants before the winter dormant period, which can then put all their energies into flowering next year, from mid-May until the end of summer.

Sow your poppies into a tray of damp, multi-purpose potting compost and cover the tray. Keep them warm and moist, checking every day for any signs of green: seedlings should appear in about 10 days. At this stage, remove their cover and put them in a cool, light place. When they first appear, the poppies will have a simple pair of leaves. Within another week, they will form their first pair of true leaves, characteristic of the mature plant. You now need to prick them out.

Buy a tray or two of one-inch cell insets (those joined-up sets of plastic or polystyrene boxes which you can rest in a seed tray). Plants seem to grow better in polystyrene. It insulates the compost and provides a cosy warm environment perfect for quick root growth.

Dislodge a clump of seedlings from the compost with a pencil, tease a single plant's roots out from the rest and replant it in its own cell (don't plant more than one per cell). When they have formed little plants, making a dome about an inch and a half in diameter, they are ready to go out into the garden.

The poppy is the most glamorous bi-ennial I grow, but there are others almost as good, which you should also think of sowing now. The modern hybrids of sweet Williams, Dianthus barbatus, that you see on flower stalls at this time of year have lost their smell, but there are some superb, scented sweet Williams if you revert to growing older varieties.

Go for the crimson-leaved, almost black-flowered Dianthus barbatus 'Nigricans' for a beautiful, rich, scented flower, or the brilliant magenta 'Oeschenberg', whose flowers sing out against dark, crimson-washed foliage. For a classic old variety of sweet William, go for the dusky purple 'Homeland'. This is an auricula-eyed sweet William, with a large white eye in the centre of each richly coloured flower.

Sweet Williams can be sown under cover, like the Iceland poppies, or sown direct into the ground, in the same way as hardy annuals earlier in the year. Sweet Williams, wallflowers, foxgloves and the sweetly scented damask flower, Hesperis matronalis, can all be sown in this way, without the need for any kit. There are three secrets to success with direct sowing. Firstly, you need a fine tilth, where the top two to three inches of soil has the consistency of apple crumble topping. To prepare the seed bed, dig it over, bashing any large clods with the back of your fork. Rake it in one direction to get rid of any remaining lumps and again at right angles.

Secondly, sow the seed as thinly as possible, individually placing the seed if you can. Foxglove and wallflower seeds are small, so sow these a pinch at a time, moving quickly along the row for a fine distribution. Never pour seed from the palm of your hand. This will give you uneven blocks of seedlings.

Thirdly, you must thin when the tiny plants have one pair of true leaves. Choose a strong-looking plant to leave every three to four inches, but remove all the others. In a couple of weeks you should thin again, leaving 10 to 12 inches between plants. At this stage the seedlings are large enough to survive transplanting. Dig up the plants in September and place them in large, generous blocks or drifts among shrubs and perennials in the garden. Wallflowers will flower in the middle of March. The other biennials will follow in mid-May.

These, and other biennials, can be obtained from Sarah Raven's Cutting Garden, Perch Hill Farm, Brightling, Robertsbridge, East Sussex TN32 5HP (01424 838181) or e-mail Ravenflora@aol.com.

The garden centre benches are full of tomato plants at this time of year. If you have a greenhouse, these are a must. If you have a sunny, south-facing wall it's also well worth trying to grow tomatoes outside and late May is the time to plant them. By then the fluctuation between day and night time temperatures is much less than even two weeks earlier, when the frosts will have finished in most places. Tomatoes like things regular and only do well if temperatures, and your watering and feeding habits remain about the same from now until they finish fruiting in September.

Choose a reliable variety like Alicante or Gardener's delight. These are widely available. If space is restricted, go for one of the cherry forms which take up less room. Plant them in a sheltered spot in full sun, tying them into a cane as they grow. Do not put them anywhere near potatoes in the garden. Potato Blight was rife last year, in the damp summer and early autumn. This can cross infect tomato plants and every fruit will go black in a couple of days.

With Alicante or Gardener's delight, pinch out any buds that form in the angle between the leaves and the main stem. This diverts energy away from fruiting. Do not do this with the cherry forms; they have a bushier habit.

Water your plants every day and feed them once a week with a seaweed- based fertiliser like Liquinure.

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1 The garden centres are full of tomato plants at this time of year. If you have a greenhouse, these are a must. If you have a sunny, south-facing wall, it's well worth trying to grow tomatoes outside, and late May is the time to plant them. The fluctuation between day and night temperatures is much less than even two weeks previously and tomatoes do well only if temperatures, and your watering and feeding habits, remain almost constant from now until they finish fruiting in September

1 Choose a reliable variety like 'Alicante' or 'Gardener's Delight'. If space is restricted, go for one of the cherry forms. Plant them in a sheltered spot in full sun, tying them into a cane as they grow. Do not put them anywhere near potatoes. Potato Blight can cross infect tomato plants and every fruit will go black in a couple of days

1 With 'Alicante' or 'Gardener's Delight', pinch out any buds that form in the angle between the leaves and the main stem. These divert energy away from fruiting. Do not do this with the cherry forms; they have a bushier habit

1 Water your plants every day and feed them once a week with a seaweed- based fertiliser such as Liquinure