Sarah Raven's Kitchen and Garden

At the end of July you’re coming up to the last moment for sowing the later flowering biennials - foxgloves, sweet rocket, sweet Williams and euphorbias - which take up the baton of colour as spring slides into summer.

The oast courtyard here is the only part of the garden which is purely ornamental not productive. It’s designed and planted on the bold and brilliant principle, with lots of sumptuous flowers and foliage in strong Venetian colours – purples, magentas, deep blues, crimsons, vermillion-oranges, all set against plenty of enlivening acid-greens and silvers. The trouble is it doesn’t achieve the drama and abundance I’m wanting every month of the year. The winter isn’t great, but I wouldn’t expect it to be. I need more structural plants and architecture for the lean months. The late autumn isn’t perfect either, perhaps too dominated by hydrangeas, dahlias and chrysanthemums, but it’s the late May dip that really troubles me. I feel the garden should be at its best at this point in the growing year. I walk out into the lane and the countryside could not be more beautiful. The hedge is a white froth of hawthorn blossom and the road edge, one airy cow parsley cloud. Back in the garden, it’s bland in comparison. The spring bulbs and blossom are over. The last to flower Parrot tulips, ‘Orange Favourite’ and ‘Texas Flame’ have dropped their petals and there isn’t enough to follow on. Allium ‘Purple Sensation’ is just emerging, and I have a few good patches of Oriental poppy and some euphorbias, but I need more. The colour and exuberance just isn’t there.

That’s where these later-flowering biennials are set to help me out. The invaluable thing about these plants, that you sow now to flower next, is that they bloom at just the right time to fill the colour hiatus between the end of the spring bulbs in mid May and when the roses, lilies and bulk of the perennials come into their own in the middle of June. As long as you sow your biennials by the end of this July, you’ll be awash with colour for just that moment, and all for the cost of a few packets of seed.

Intense blue will come from Anchusa azurea. This is a short-lived perennial which I treat as a biennial to guarantee plenty of it every year. It always looks best intermingled with other plants and I’m going to try it with late August sown, Papaver somniferum ‘Black Peony’. Both plants reach five foot and the airy verticality of the anchusa would be perfect as a blue cloud around the whopping crimson-black pompoms and silvery seed pods and foliage of the opium poppy. They’ll both be at their best from May until July.

I’ll have a big drift of the sweet rocket, Hesperis matronalis in the shady side of the garden under the oak tree, with the angular and dramatic biennialEuphorbia lathyris. I love both these plants for their tolerance of the shade and the sweet rocket is invaluable for giving so much colour - bright mauve and scented flowers – in a dark position. I’ll pick or dead head both to keep them going for as long as possible from May right through the summer.

On a smaller scale, there are a couple of sweet Williams I want in here and another euphorbia and marvellous poppy. I like the idea of the power packed colour of magenta Dianthus ‘Oschberg’ with the vermillion Iceland poppy, Papaver nudicaule ‘Red Sail’. I’ll also have a few plants of the high class, deep crimson velvet sweet William, Dianthus barbatus ‘Nigricans’ set against the acid-green haze of Euphorbia strictus. This is the most delicate of euphorbias, forming light acid-green domes about two feet high and it gently self sows. It would be perfect drifting behind the dark sweet William so that their rich coloured flowers don’t get lost against the soil.

I’m going to plant a bank of white foxgloves, Digitalis purpurea f. albiflora at the entrance to the garden. I love the creamy whiteness and the tall vertical spires of this foxglove, which always look best en masse, but I have a rule of no white – it’s too glaring amidst the rich Venetian tones - actually within the oast garden walls, so they’ll have to be kept just outside.

I’m sowing one final plant, Echium pininana, the most dramatic of the lot. This is not biennial, but triennial and so won’t flower until the year after next, but these echiums are worth the wait. I love these vast plants with their ten or even fifteen feet telegraph poles of bright blue and two or three would be perfect for the oast garden. One of the best shows I’ve ever seen of this variety of echium – which are tender - is in the frost-free Abbey gardens on Tresco in the Scillies, but they also grow well in the garden at Glyndebourne opera house, just down the road from me in Sussex. At Glyndebourne they prolifically self sow and enough seedlings survive from one year to the next to give a spectacular firework display from late spring right through the summer.

July is already too late to sow your biennials direct so I’m sowing mine into large shallow trays and will prick them out into decent sized 1 litre pots from there. That will give them enough root room to be happy until the end of August. Until the seedlings get well established, sweet rocket – a brassica – will need protecting from flea beetle with fleece.

By the end of August, it’s important to find gaps for all your plants. Planted at the end of summer, the soil is still warm and the moisture levels are on the up. The roots settle in quickly and the growth rates are superb before the cold nights shut things down as you move into autumn proper. I used to put my biennials into their final flowering place in early October, but by the spring, they’ve only made plants half the size of those planted out four or five weeks before. Get them in as soon as you can and a dull late May in your garden will be a thing of the past.