How to Sow and Grow Sweet Peas

How to plant fragrant sweet peas in the garden

February 25, 2020

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Few annual flowers have the lasting appeal and bucolic beauty of sweet peas. Twining lazily around a rustic trellis made of hazel poles, they seem the very antithesis of the busy, hectic lives that we now lead. They are now available in a huge range of colours from pearly white through ice cream pastels to ritzy magentas and inky purples.

A Short History of Sweet Peas

The first sweet peas were introduced to Britain in 1699 when a Sicilian monk, Francis Cupani, sent seeds of this highly fragrant annual to Dr Robert Uvedale, a teacher from Enfield, Middlesex.

They became hugely popular in North America, both as garden plants and cut flowers. By the late 1800s, California’s growers (including W. Atlee Burpee) shipped trainloads of sweet peas all over the country and developed many further varieties.

The combination of the delightful scent and the ability to produce so many blooms for the house over a long period of cutting has ensured their popularity. Although many of the modern varieties have larger flowers and contemporary hues they lack the fragrance of the earlier sweet peas. Sweet pea “Cupani”, with it’s bi–coloured flowers, maroon upper petals with violet “wings” is still deservedly popular and is easy to grow.

Size matters and there are sweet pea varieties for every situation, from 8-foot-plus scramblers to dwarf bedding ones suitable for containers and borders without support.

Do Sweet Peas Come Back Every Year?

Most people grow the fragrant sweet pea, lathyrus odoratus, which is an annual. Event though these sweet peas do not come back, you may save your seeds to sow next year!

However, there is also a perennial unscented broad–leaved everlasting pea, Lathyrus latiflolius. These are clambering plants, which can reach up to 3 meters. Hardy to zone 5, they are not frost tender and are low maintenance, flowering regularly year on year.

When to Plant Sweet Peas

If your location does not experience frost, then sweet peas will benefit from being sown outside in November in the area where you would like them to grow. To get the best display dig a trench and fill it with well-rotted manure or compost 6 weeks before you sow the seeds. Sweet peas are greedy plants and need a good boost of nutrient rich matter to thrive.

However, for most locations where frosts occur, sweet peas should be sown inside for protection. Many sowings of mine that have shown great promise have been devoured in a single sitting by mice that find them irresistible. Soaking the seeds overnight first softens the outer coating and aids germination. Then plant the seeds about half an inch deep in individual modules in a seed tray, 2 seeds to a module is fine but no more as their long roots have a tendency to tangle.

Once they are showing their first pea like leaves gently scoop them out and put them into a larger pot to harden off. The advice I had from one of the most respected sweet pea growers was “to treat the seedlings how I would my husband: stick them in an unheated greenhouse, ignore them and they will thrive.”

When the danger of frost has passed plant them outside in either a compost trench or soil enriched by compost or well rotted manure. See the Almanac’s Sweet Pea Growing Guide for planting instructions.

Do I Need a Trellis for Sweet Peas?

Yes, give them some sort of structure to climb up—bamboo poles in a tee–pee style, a woven willow obelisk or hazel poles in a trellis are all visually pleasing. Tie the first few stems in to the support to give the plants a good start and the rest will follow. When they get to 4 to 8 inches high pinch out the middle growing tip with your thumb and forefinger. This will lead to sturdier plants.

When sweet peas flower, keep picking them. The more you pick the more they produce, right until the first frosts. When the leaves start to lose their color let a few of the last flowers form seedpods. Dry them on a windowsill and then store in an envelope in a dry place to sow next year.

Try out the Almanac Garden Planner for Free

As a courtesy, the online Almanac Garden Planner is free for 7 days. This is plenty of time to play around on your computer and try it out. There are absolutely no strings attached. We are most interested in encouraging folks to try growing a garden of goodness! 

Try out the Garden Planner on your computer (for free)!

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