Sweet peas are one of summer’s delights and to enjoy the flowers at their fragrant best, sow seed within the next few weeks. If possible, sow rather than buy young plants that are started in peat-based compost and sold in black plastic pots.

And, rest assured, there’s nearly always space to sow your own – you don’t need a greenhouse.

Many English gardeners sow sweet peas the previous autumn, but spring in this country is rarely warm enough for planting outdoors. February-sown plants here put on a good, all summer long show.

Because sweet peas are so popular, there’s a seemingly endless choice of varieties, which cater for every colour and colour combination you could want. The original heritage varieties such as ‘Cupani’, bi-coloured purple/maroon, and ‘Painted Lady’, bi-coloured pink/white, produce smaller but highly scented flowers.

There are many more colours in the more modern Spencer varieties, but some have very little scent. A virtually scent-free ‘sweet’ pea does seem ridiculous! This may also apply to the new selection of dwarf sweet peas bred for pots, ground cover and even hanging baskets.

Use a propagator in a greenhouse for strong early growth. But don’t despair if you don’t have one. A windowsill also does the trick, but in either case, don’t put the seedlings too close to the window where it’s much cooler. This is especially true in a greenhouse with no double glazing.

Sweet peas have long, slightly brittle roots that should be transplanted as little as possible to avoid damage. Use multipurpose or homemade, not seed sowing, compost to provide nutrient for longer.

And peat-based compost is obviously off-limits for responsible gardeners.

Use long narrow pots to let roots grow down vertically as is their wont. Large plastic root trainers are possible, but as I’ve said many times, wherever possible plastic should be off a gardener’s shopping list. This was borne out last week by the international Environmental Investigation Agency which called for a binding treaty to reduce the production of plastic and waste management. Even re-using older plastic is questionable as it sheds dangerous micro and nano particles into the soil.

There are now sustainable alternatives available. Sarah Raven has excellent sweet pea tubes. They are narrow 12.5cm long pots made from wood pulp that almost looks like paper.

Side roots spread freely as pots start disintegrating. J. Arthur Bowers also supplies Fyba grow tubes and Vitax Grow-Tubes are so widely available you can even get them from Amazon.

Control yourself when deciding how many plants to grow. Each one becomes tall or bushy, depending on variety and how you grow them. You always need fewer plants than you imagine as they’re spaced 20-25cm apart to avoid a total jungle.

When sowing, place the seed in a saucer, put in a little water and cover with kitchen towel. This softens the seeds’ outer shells to speed up germination. Make holes in the compost and put in 2 seeds per pot. After 5-10 days, the seedlings should appear. Water to keep compost moist but not wet. After 2-3 pairs of leaves have formed, snip off one vine, leaving one plant per pot.

Sweet peas tolerate light, but not heavy, frost so plant out in April when there’s little risk of this. You may want to pinch out a pea’s leading shoot.

This prevents it from growing so tall and produces a bushier specimen. Pinch out the leader just above a node and several smaller, lower-growing stems are stimulated into growth. This method is up to you – I never do it as I want tall plants for screening.

Plant of the week

Snowdrops, Galanthus nivalis, are poking up above ground in sheltered spots. Soon the emerging flower heads will show white between the green leaf tips that are hardened so they can push through frozen ground.

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