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Planting, Growing, and Caring for Sweet Peas
Early sowing in late winter is one of the secrets to growing sweet peas! With their seductive fragrance, sweet peas make great flowers for gardens and bouquets. These exude a pastoral beauty—an antithesis to our busy world. In our growing guide, learn how to plant and care for sweet peas.
About Sweet Peas
The sweet pea—Lathyrus odoratus—is an annual flower that is at home in a cutting garden, border garden, woodland, or twining lazily on a rustic trellis or an arch. The flowers are now available in a huge range of colors, from pearly white through ice cream pastels to ritzy magentas and inky purples.
Their dainty winged blossoms are matched only by their honey and orange blossom perfume. 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.
Despite their delicate look, sweet peas are quite hardy. In USDA Hardiness Zone 7 or colder, plant them in very late winter or early spring as soon as the soil is dry enough to work.
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, as both 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.
Some folks say that growing sweet peas is akin to making a pie crust. Some people have the knack, while others don’t. This plant grows from large, easy-to-handle, pea-like seeds. Still, they’re a bit tricky because they are slow to germinate. It’s worth experimenting with different seeds each year.
Planting
WARNING: Do NOT plant sweet peas near edible garden peas. All parts of the sweet pea plant are poisonous. If enough of the plant is consumed, it can cause a condition called lathyrism, which is exhibited by paralysis, shallow breathing, and convulsions.
When to Plant Sweet Peas
- In most locations where frosts occur regularly (Zone 7 and colder), sweet peas should be planted in very late winter or very early spring as soon as the soil is dry enough to work. (Do not wait until the last frost to sow! It will likely be too late.)
- If you garden in mild winter climates (Zones 8, 9, or 10), plant sweet peas in the late fall (November) so they can develop and bloom in late winter and early spring. 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.
Sowing Sweet Peas Indoors
- In the coldest parts of the country, get a jump on the season by starting sweet peas indoors in a seed tray. Sow in seed-starting containers in early spring, about 6 to 7 weeks before the last frost date, then plant out as soon as the soil can be worked; sweet peas can handle light frosts.
- Soaking the seeds overnight first softens the outer coating and aids germination. Lightly scoring the outer shell with a nail file can help, too.
- Sow the seeds about half an inch deep in individual cells of a seed tray—2 seeds to a module is fine, but be aware that their long roots have a tendency to tangle and can make separation difficult.
- 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.”
- As soon as the soil can be worked, plant them outside.
Sowing Seeds in the Ground
- Sweet peas are happiest with their heads in the sun and their roots deep in cool, moist soil. When possible, plant low-growing annuals in front of them to shade their roots.
- Choose a well-drained site. Alkaline soil is best; sprinkle some powdered lime on the surface if your soil tends to be acidic.
- Prepare a rich soil by mixing in generous amounts of compost or well-rotted manure to a depth of 2 feet. (If you want to learn more about preparing soil for planting.)
- Prior to planting, you’re going to want to dig a nice deep “compost” trench of about 4 inches in depth.
- After you dig the trench, make holes with a pencil, drop in the seeds, and press down on the soil to firm it and shut out any light.
- Before planting, soak the seeds in water for 24 hours. Then nick the seeds with a nail file before planting to speed sprouting. You do not need to soak seeds in a temperate climate.
Joins us as we show you how to plant sweet peas in this video demonstration:
Growing
How to Grow Sweet Peas
- Once planted, germination can take 7 to 15 days, depending on the soil temperature.
- As seedlings emerge and grow, gradually fill in the trench. Hoe more soil up to them.
- Keep soil moist. Summer rain may be ample. If you put your finger into the soil bed to its first joint and the soil is dry, water them at the soil level and do so in the morning; sweet peas can suffer from bud drop.
- If you use plenty of aged manure and compost when planting, you do not need to fertilize. If you do want to add nourishment, use high potash feeds, as nitrogen feeds encourage too much top growth.
- When plants become established, mulch well to keep the soil cool and moist. If you mulch, you may not need to water your sweet peas unless the soil gets dry.
- To encourage bushy growth, pinch off the tops when plants are 6 inches tall—not before, or you’ll encourage premature side-shoot development.
Provide Supports
- Sweet peas prefer cool days and nights and will start to fade when temperatures go above 65°F.
- Except for the bush types, sweet peas are real climbers. Give them at least 6 feet of good support. Some varieties may climb to 9 or 10 feet. Other visually pleasing supports are bamboo poles in a tee-pee style, a woven willow obelisk, or a trellis. If you don’t have a fence or trellis, provide chicken wire or bushy, stubbly twigs that they can cling to.
- Tie the first few stems into the support to give the plants a good start, and the rest will follow. When they reach 4-8 inches high, pinch out the middle growing tip with your thumb and forefinger. This will lead to sturdier plants.
Picking Flowers
- Pick the flowers for bouquets often, and the plant will put energy into more blooms instead of going to seed. 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 them in an envelope in a dry place to sow next year.
Catherine Boeckmann
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I love to plant flowers and veggies. I have enjoyed and learned from reading your tips and instruciton. Thank you.
I am a total gardening novice, so forgive my question - my sweet peas have pods on them and I have cut them off - are these to be used for next years crop? Do I leave them to dry out? Thankyou in advance, cheers, Jan
I live In Darwin but I love sweet peas. I'm going to give it a go.
I do not purchase any products of Monsanto due to the devastating impact that company has had throughout the world especially with their product Roundup which continues to be on the market despite proven lawsuits. What do you recommend as an option to Miracle Gro?
Will my sweet pea vine bloom more flowers if I pinch off the pea stems as soon as I see them?
The seed doesn't need to be cut open, unless you want generally weaker plants. I germinate EVERY SEED I grow by putting a paper towel in a Tupperware container, soak the towel with miracle grow water, add the seeds, snap the lid on and then put in the sun. I put sweet pea seeds out this morning using the above method and a few of them have split open on their own already. I also use this method to weed out the slower growing "weaker" plants
how can I stop 6ft.high sweetpeas growing to that height.can I just nip them off at 3ft
Cutting them at the preferred height will encourage the plant to grow more from the base, resulting in a bushier plant. However, it won't just stop growing where you cut it. You'll have to maintain the height by periodically trimming over-growth. As long as you leave the plant with a few leaves, and don't mangle it, cutting/trimming the plant is fine.
We live in the UK and grow sweet peas every year. At one spot in our sweet pea bed the plant always dies, the others are fine. Can you suggest any reason please.
There must be an underlying issue with the spot. It could be a number of things… Does water tend to pool there? Or are there roots or rocks in that spot that prevent the plants from rooting well enough to survive the heat of summer? Is the spot exposed to more—or less—sunlight than elsewhere? Does a pet like to use that spot to do his or her business? Consider what might set that spot apart from the rest of the bed, and also remember to amend the soil with compost or fertilizer every now and again.
