Wednesday, 12 February 2014

5 reasons why you should grow sweet peas this year

Over the past week, between prolonged periods of blustery wind and torrential rain, there have been a few occasions where the sun has shone. Not many – not nearly enough – but sufficient to engender the tiniest spark of hope for days of an altogether different nature – fresh, sunny days, firm underfoot, where the wettest hour of the day sees twinkling beads of morning dew hanging poised, as if deciding whether to roll gently to the earth along stem or blade, or hurl themselves into the unknown and plop fatly to the floor. I want to wander along winding paths flanked with flowers, surrounded by scent and colour and the buzzing of bees. And the flowers I imagine, translucent petals backlit by the sun, are always sweet peas.

I’m not sure I had a clue what a sweet pea looked like when I first picked up a gardening book. They are not typically showy flowers, though en masse, clambering over supports in the garden, or gathered together to display in a vase, they present a spectacle that belies their somewhat humble background as a cottage garden favourite. This is an annual, climbing plant in the pea and bean family; long, somewhat angular and strangely brittle stems of a pale blue green twining around any obstacle into which they come into contact, gripping on with delicate looking tendrils of surprising strength. Fascinating as the structure of the plant is, a person could be forgiven for thinking the leaves and stems unlovely. But the profusion of flowers produced is an entirely different matter. If you hadn’t already been planning to grown them this year, here are five reasons why I think you should.

1. They cost practically nothing, other than a little time.

2. They look amazing, adding colour, height and structure to your borders.

3. Choose the right varieties, and they smell divine

4. They go on, and on, and on... Flowering begins in May, and last year we were still picking blooms into the latter half of October.

5. They make fantastic cut flowers for your house, or as a gift for friends and family.

I hope this might have at least persuaded you to consider these amazingly rewarding plants for your garden this year. If so, you may have some questions as to how to get the best from them, which I’ll attempt to address below.

A quick guide to growing sweet peas

What to buy?
Nurseries and garden centres will begin to stock plants in early spring. This is a relatively low cost way to get hold of plants. But you’ll get a much greater selection of varieties if you grow from seed, and have more fun along the way.

Which varieties? 

Part of the fun of growing sweet peas is choosing from the many different varieties available. The catalogues of seed companies are a fantastic source of inspiration and many, if not all, are of course available to search and peruse online. The names given to various different types of sweet pea – Grandiflora, Spencer, Old fashioned, Modern etc – can be bewildering at first, and though they are of some use to the gardener (Spencer types, for example, are generally more flouncy and often larger flowered than Grandifloras) my advice is to ignore them. Concentrate instead on the descriptions of colour and of scent, the two main criteria you need to employ when making your choice, and of course, any accompanying photographs. But do be aware that some varieties have been bred with an emphasis on the colour, size and form of the flower, often at the expense of the scent, which to me seems a shame. Labouring to create a sweet pea without scent seems as sensible an activity as breeding a zebra without any stripes.

When to sow seeds? 

Impressively well-organised gardeners will sow a batch of sweet peas in the autumn, around October, for flowering the following summer. This is a great way in which to give your plants a good head start over plants grown from seed sown in spring. The seedling plants will of course need to be kept moist (not drenched) and frost free over the winter and, when there are three or four pairs of leaves, the top pair should be pinched out – literally pinch the stem with your thumb and index finger just above a set of leaves and remove the top of the plant – which stops the plant from becoming long and gangly. This means remembering to visit the greenhouse throughout the winter, but if that’s not something you think you’ll do, all is not lost. It’s perfectly acceptable to sow seed in February or March under cover, in a greenhouse or on a bright window ledge and, for the terminally disorganised, you can even sow the seeds straight into the soil (direct sowing) where you want them to grow in late March or April, although with more variable results.

Someone needs to remind this sweet pea about hypogeal germination...


How to sow seeds

You may hear from They Who Know (you know who I mean, don’t you?) that you have to soak sweet pea seeds in water overnight before sowing, or chip the seed coat with a knife in order to ensure germination. I’ve yet to find this necessary with any of the varieties I have grown, and have enjoyed an almost 100 per cent germination rate. Soaking the seeds is generally deprecated now, the RHS guidelines suggest it could lead to rotting of the seed. But in gardening, fashions come and go, so we’ll probably be telling people to do it again in ten years or so, though I do hope not. It’s a bit of a faff; the kind of thing that makes gardening seem like a dark art and puts lots of people off.

The main thing to know is that sweet peas are fussy about their roots. They like a lot of room, and once the root system is established, they really hate any disturbance. (This, incidentally, is why you shouldn’t split young plants bought from the nursery or garden centre, as it seriously checks the development of the plant and effects how quickly your sweet peas will get away once planted out.)

In the past I have sown my sweet peas into pots made from recycled newspaper, using one of those ingenious wooden seed pot makers. These did ok, but lacked the ideal depth, so I progressed to cardboard toilet roll inners, with pretty good results. The only difficulty I find is that in damper, cooler conditions, any overwatering causes the cardboard roll to unravel leaving you with a mess of seed compost and roots rather than a nice, firm jumbo plug in which the roots are safely contained. I think this may have set the plants back a little, and so this year, with a bit of an initial outlay, I have invested in plastic root trainers – effectively a system of tall modules ideal for plants with longer roots. (If you find yourself particularly infatuated with this aspect of growing sweet peas, you might like to read Petra Hoyer Millar's take on it here).


How to protect young plants

Sweet peas are clearly delicious to garden critters, though poisonous in quantity to humans. Use mousetraps or a well trained cat in the greenhouse, non-metaldehyde slug pellets or midnight garden slugging visits in the garden, and consider a low barrier of chicken wire, a garlic and chilli spray or poachers if you share your outdoor space with rabbits.

How to offer support

Sweet peas are climbing plants, and you will need to provide something for your sweet peas to grow up. Otherwise they’ll wander across the ground and clamber up the first vertical surface they find – plant, spade, slow-moving relative – anything. You could be posh and use a metal obelisk, but I prefer something a little more rustic. A woven willow wigwam smothered in colourful blooms looks fantastic, and although the plants are just as happy climbing up bamboo canes tied in an similar arrangement, I like to use native materials. If not willow, I’ll most often use thicker poles of ash or hazel, about six foot high, five pushed into the ground around an imaginary circle 60cm in diameter, and then lashed together at the top with lots of thick, tarred garden twine, which I then wind helter-skelter fashion around the structure to give the plants more to clamber up.

Tarred garden twine from Penny at Le Petit Jardin, Tunbridge Wells
Woodland coppice products (hazel bean poles, willow etc) from John Waller the underwoodsman at Bore Place, Chiddingstone
Ash poles from the edges of the garden, or growing up in the middle of random shrubs. They get everywhere! Recognise them by their smooth grey-green bark, strong, upright growth and beautiful matt black buds, slightly leathery to the touch, like the underside of a dog’s paws.

How to plant and how to water

Make sure the soil is well dug over, preferably with lots of organic matter, compost, or chicken manure dug in. Sweet peas do enjoy a rich soil, and it won’t hurt to give them an extra feed every few weeks with a drench of a seaweed based feed or compost tea. I plant three to a pole, and tie the shoots gently into the supports. Watering in well at the planting stage is a simple task; in summer, when the supports are covered in foliage and flowers it’s tempting resort to the spray on hose or sprinkler. You must avoid this temptation, as a combination of dry roots and moist air around the plant encourages powdery mildews. Instead, make a point of watering at the roots – it might not be so much fun, but it will keep the plants healthy for much longer.

Harvesting, tying-in and deadheading

As well as harvesting your sweet peas for the house (great, scented bouquets by the handful once they get going in summer, how wonderful), and tying wayward stems back into the supports to preserve some order, you need to remember to deadhead the plants regularly. As soon as flower starts to fade, ideally before the petals drop, cut it from the plant at the base of its stem, or it will set seed and divert energy from the flowers. By midsummer, if you neglect this task, your glorious floral display will have been replaced by a hearty crop of seed pods, looking like silky grey green mange tout. Keep on top of the deadheading and you can maintain a harvest of flowers right into autumn.

If you have any tips for growing sweet peas, or favourite varieties, please do leave a comment below or tweet @growgardencare.