How to grow sweet peas

The scented flowers of sweet peas are the very essence of summer, whether wafting their fragrance through the garden or the rooms in your home. Easily grown from seed sown in the autumn and spring, these pretty climbers are perfect to add height to borders. They can also be grown in large containers on a patio or balcony, while some of the dwarf varieties are good for window boxes and hanging baskets.

They do need at least 2-3 months to grow from seed before they will come into flower. The later in spring you sow them, however, the quicker they will grow in the warm and light conditions. If sown in early April, you should be picking the first blooms in mid- to late-June. And if you don’t want to grow your own from seed then they are available to buy as young plants at garden centres and by mail order.

Where to grow sweet peas

These easy-to-grow plants, do need plenty of light if they are to do well. They don’t enjoy shaded conditions or a position where they are overhung by the dripping leaves of trees. A place in the open, with sunlight for at least 6-8 hours in the summer will suit them well. Growing in the open also helps to reduce health problems by allowing air to circulate through and around their leaves. They may often suffer from mildew if grown close to a fence or wall, as well as in poor soil. The best way to grow them is on a freestanding support of canes or stings.

They do best also in soil that has been improved with plenty of well-rotted garden compost or bagged organic matter. Too much richness in the form of manure – however well rotted – usually makes them grow rather soft and thus prone to aphids and other pests, in my opinion.

If you have to grow in pots, then the ordinary varieties are best cultivated in large containers – at least 45cm (18in.) in diameter and as tall. This provides the plants with a good volume of compost to keep moisture at the roots. In small pots they are liable to drying out quickly and this puts the plants under stress in summer making them more liable to mildew. Dwarf varieties can be grown in smaller containers of good quality compost and kept well-watered to prevent them from drying out.

Ways to sow sweet peas

If you are going to grow your own sweet peas from seed then it is a good idea to soak them in water first. Simply put the seeds in a mug, covered with a little tepid (very slightly warm) water. I leave them overnight, but 2 hours minimum will usually do. This rehydrates the seeds so the inside expands to split the hard seed coat. Many books and references will suggest ‘nicking’ or cutting the seed coat but this can risk damaging the inside of the seed. Soaking does away with nicking.

I use a good quality seed compost for all my sowing. In particular I enjoy using Dalefoot Composts that are made from composted bracken and sheep’s wool, and which are peat free. Their seed compost is really good, but I still mix it 3-parts by volume with 1-part of horticultural sharp sand for sweet pea seeds to provide good aeration for quick germination. Use a flowerpot to measure out the volumes. I also tend to sieve all my composts before using them using a medium garden sieve. This helps to break down any lumps and aerates the compost when the seeds need to germinate.

I then fill Rootrainers (shown in the main image here) – available from some garden centres as well as from Haxnicks or Agriframes – or the cardboard tubes from the inside of toilet rolls with the compost. The Rootrainers are some old ones that I have had for years and re-use time and again, washing them out between use. The toilet roll tubes I usually stand in a wooden box prior to filling so that they stay upright. Don’t firm the compost in place with your fingers as this tends to push out the air. Instead, tap the filled containers to settle the compost in place.

I prefer to make holes in the compost surface with the pointed end of a pencil, about 2-3cm (1½in.) deep, and then drop a pre-soaked sweet pea seed into each. Aim to sow a pair of seeds in separate holes in each section (each Rootrainer or cardboard tube). After sowing, water the compost thoroughly and that will also cover the seeds. Put them in a warm place (around 15-18C for speediest results), and the seeds should germinate in a week or 10 days.

What are the best sweet peas to grow

There are lots of different strains and varieties of sweet peas. They vary hugely by their flower colour, shape, height and stem length. Garden centres, DIY stores and on-line seed suppliers offer an excellent range. But probably the most important consideration for many people is the scent of blooms and there is plenty of opinion about the best scented sorts. I love ‘Cupani’, ‘Matucana’ and ‘Lord Nelson’ – the latter being a particular favourite as I have strong family connections with North Norfolk.

Whatever sweet peas you end up growing, make sure that you keep picking them in the summer. That way you’ll ensure that more buds will come, and there’ll be plenty to bring indoors to enjoy.