Growing Sweet Peas

Sweet peas are one of the most popular spring-flowering annuals. With their long stems and brightly coloured blooms they put on a fantastic display in the garden and make excellent cut flowers.

They come in a range of gorgeous colours including white, pink, lilac, red and blue but never yellow.

Regarded as old-fashioned by some, sweet peas are currently enjoying a flush of popularity thanks to new breeding programs that have resulted in bigger, brighter blooms.

The larger, showier varieties have long wands of bright, fluttery blooms that don’t tend to be as fragrant as the more traditional types like matucana.

Heirloom vs hybrid

‘Sweet peas are starting to come back into fashion with newer varieties that have been specially bred for larger flowers,’ says grower Justin Russell.

Justin and his wife Kylie have been growing sweet peas for 14 years, and run Thistlebrook Nursery in Hampton, Queensland.

The new varieties are popular but purists will always choose heirloom types for their traditional form.

‘Heirlooms are the non-hybrid sweet peas. You save the seeds of the heirloom or heritage varieties and re-sow them so you’ll get identical or nearly identical plants to the ones you’ve grown previously.

‘With hybrids, if you were to save the seeds at the end of flowering and replant them you would have seedlings that would grow like either of the parents, so they won’t necessarily come true to type.’

Justin grows matucana varieties and the blue-flowering Flora Norton, as well as pink, red and purple ‘Painted Lady’ sweet peas.

Time to sow

Sweet peas are associated with St Patrick’s Day on March 17 because for many growers this is planting time.

‘We do the traditional planting this month. For most climates along the east coast it’s the ideal growing time. But in a cold climate like Tassie you plant in spring and grow them until late spring or early summer.

‘The best environment for them is anywhere you can raise shelling peas, so a warm to cold temperate climate is ideal,’ says Justin.

Soil conditions

Sweet peas are best grown in a soil that is slightly alkaline. They also love water and will grow vigorously in the right conditions.

‘One of the mistakes people make is they load the soil up with lots of nutrients. The plant then responds by putting on lots of foliage at the expense of flowers,’ says Justin.

‘Add compost or really well rotted manure prior to planting. Wood ash is also good as it’s based on calcium carbonate and potassium carbonate.

‘The calcium makes the soil slightly alkaline and the potassium is really good for enhancing the potash, which helps the plant produce more and better quality flowers,’ he says.

If the soil pH is too low, at about five, add dolomite. If the soil is heavy and loamy, add gypsum.

When it comes to water, keep it flowing. ‘The more water they get, the bigger they’ll grow. In a wet season they’ll go crazy and grow way beyond the top of their trellis,’ says Justin.

Humidity is not a friend of sweet peas and they’re prone to diseases like powdery mildew in a semi tropical or tropical environment.

A lovely cut flower for indoors, the plant responds well to being picked.

‘The more we pick them, the more the plant flowers and the longer the season extends but if you leave the flowers on the plant they go to seed.’

TIP Sweet pea seeds can be picked and stored for sowing next season.

purple sweet peas and white frescias, handyman magazine,
Purple sweet peas and white freesias make a gorgeous scented combination. Image: Chris L Jones

Growing on a trellis

For a standard trellis, Justin sows two seeds at a time positioned 100mm apart, thinning them out by removing and discarding the weaker of each pair of seedlings.

‘If you’re doing a tripod trellis which can look really nice, you just plant three seeds, one at the foot of each tripod,’ he says.

‘Sweet peas have tendrils like a pea so they’ll cling on to whatever’s there but if you have a tripod you need to tie them on.’

Justin recommends using tights, jute twine or soft twine made from recycled T-shirts from nurseries.

‘The idea is to give support initially then eventually the plants will cling on their own as they climb up the trellis,’ Justin says.

TIP Sweet peas only need a basic trellis as they’re not heavy plants.

sweet pea growing on a trellis, handyman magazine,
Tether sweet peas to a trellis for support until the tendrils take over. Image: Geety Images

Planting techniques

Sweet pea growers in colder climates plant the seeds in a punnet to get a jumpstart on the season.

‘They grow them indoors then plant them outside when it gets a bit warmer,’ says Justin.

‘They take about seven days to germinate then you leave them in for another two weeks to a month.’

Planting them directly into the ground is easier as they are big seeds that are simple to sow, just keep them moist until germination.

Says Justin, ‘We sometimes soak the seeds overnight before planting them into the ground. That’s another way to give sweet peas a real boost.’

planting sweet peas, handyman magazine,
Planting sweet peas directly into the ground is easier as they are big seeds that are simple to sow

This article originally appeared in Australian Handyman magazine’s March 2013 issue