Plant guide: Sweet peas

Sweet peas are a real staple in the gardening calendar.

Everyone has their own favourite varieties, their own tricks and hacks to get them growing best, and – most hotly contested! – their own preferred time to sow them.

If you’ve not tried sweet peas before, they’re a really easy plant to grow from seed, and a happy plant will give you hundreds of beautifully scented flowers ready to cut and bring into the house day after day in the Summer.

Botanical name: Lathyrus odoratus are the annual sweet peas. You can also get a perennial variety (which we’ve found pops up as a weed quite often as well!) which is Lathyrus latifolius. Though it looks similar, this has unscented flowers, so most people grow the annual type for their glorious smell…

Plant type: Annual. Sweet peas are grown from seed each year, germinate, grow a huge amount, flower and then die all within the same year. Next year, you’ll need to sow new seeds and start again.

The exceptions are the perennial sweet peas (see above), which will grow back year after year, dying down each Winter.

Growing conditions:

Sweet peas need plenty of sun to flower well. Choose an open position, with a sturdy support for them to climb up. Ideally, they need a fertile, moist but well drained soil, though if you’re growing in pots or in less fertile conditions, you can just feed them more frequently.

How to grow / plant:

Seeds can be sown in either late Winter or early Spring. Sweet peas have long roots that don’t enjoy being disturbed, so root trainers are often used – these are plastic pots that pull apart at the sides and which have a long growing space for the seedlings to establish their roots. You can find them from most gardening shops. Root trainers aren’t essential, though, an often used DIY method is the cardboard inner from toilet rolls, filled to the bottom with compost. An extra advantage of this is that you can place the cardboard roll straight into the final growing spot, as it will break down in the soil.

Sow one or two seeds in each plug, and keep indoors in a light spot until the Spring.

Choosing the exact time to sow seeds is a topic for much debate! You can sow in late Autumn, early Winter or Spring. We know lots of people who sow theirs on Boxing Day, but to be honest, we’re too busy filling up on Terry’s Chocolate Orange and After Eights in front of the TV to be worrying about gardening! We usually sow ours at the start of March.

Getting them started earlier is said to give the roots time to establish and help produce a healthier plant, ready to take off as soon as the weather is good enough for them to be planted out. Conversely, other people believe that starting them too early leaves to leggy plants that are less prone to flowering well. So, pick a date, give it a go, try a different time each year, or just sow them when you have enough time to spare!

Pinch off the top of the seedlings once they have reached about 10cm tall, which will encourage them to grow bushy and healthy plants.

Once the final frosts have passed, you can plant the sweet peas into their final position. Harden them off first for a few days to a week.

Choose an open spot, with plenty of sun, which will encourage them to flower well. Moist, fertile but well drained soil is ideal. Sweet peas can also grow in pots, just choose a large one and fill it with multi-purpose peat free compost.

Sweet peas need a support to grow up. You can use something simple, such as a teepee made from bamboo canes, buy a ready-made plant support or obelisk, or use stretches of netting if you’re growing a large amount.

Care:

There’s no two ways about it, sweet peas do need a fair amount of ongoing care!

Most sweet peas have tendrils that they use to cling, but if you are tying them to their support, then you can remove these.

Pinch out any side shoots, to encourage most of the growth to occur in the main plant.

Water well. In hot periods, or for all plants growing in pots, you will need to water once a day. Make sure the soil or compost doesn’t dry out, which can leave sweet peas prone to powdery mildew.

As soon as the first flower buds appear, feed regularly with a potash fertilizer – a tomato feed is a great option. These are hungry and thirsty plants and they don’t take neglect well! They do a lot in a very short space of time, so need lots of care…

Once the flowers have opened, cut them regularly – every day if possible. The more flowers you cut, the more will grow. And if you miss a few, make sure to deadhead any spent flowers that are turning to seed. Once the plant starts to make seeds, it will concentrate its energy on this (in order to reproduce) rather than on flowers, so it’s really important to cut off any seed heads you see appearing…

Grow with:

Sweet peas are usually grown in their own patch, rather than mingling with other plants in a border. That’s not to say that you can’t add some in, perhaps up a metal obelisk, or include pots of sweet peas among other planted containers.