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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 planted sweet peas next to my sugar snap peas. They are both blooming at the same time. I just learned the sweet peas are poisonous to eat. Should I not eat my sugar snap peas because they might be poisonous from cross pollination with the sweet peas?
I live in Houston,TX. What zone is that? It got cool for a few days. Is it just not possible to grow sweet peas here? Are there other vines that I could plant now?
Hi Laura,
You are in zone 11, which includes all of Texas. In your area, it’s best to plant sweet peas in the fall to develop in the winter. Sweet peas like cool, moist soil and can yellow easily in the heat. Another good vine you could grow now would be summer squash, which can spread out on the ground. The big leaves of squash plants naturally keep the soil beneath cool and help to prevent water evaporation. Learn more about squash growing here:
We hope this helps!
As a child I remember eating sweet pea pods from a hedge around a neighbour's garden - they were delicious! I would love to grow plants for my grandchildren to enjoy as I am trying to encourage them to enjoy gardening and the magic of growing things for themselves ... now I read that the sweetpea pods are poisonous?? I find that rather alarming so just want confirmation ... is this really true? I certainly survived the experience without any after effects ... please clarify for me.
Sweet peas (Lathyrus odoratus), the flowering plant such as pictured above, are poisonous.
Sweet peas (Pisum sativum) the vegetable, which also send up flowers before the pods (that eventually contain the vegetables), are not poisonous. You are probably remembering eating the vegetables. Click here for more information about the choices of those and recommendations for planting: http://www.almanac.com/plant/peas It’s time to plant your peas!
I live in the foothills above Sacramento, Sunset Garden zone 9. We have had an extremely wet winter/spring. Is it too late for me to plant sweet peas? Is it best to plant directly in the soil, or should I transplant from pots? These are my favorite flower!
Yes, it’s too late to plant sweet peas in your zone. As stated above, you plant sweet peas in late winter or early spring, well before frost. In zone 9, however, gardeners plant sweet peas even earlier in mid-fall to maximize winter and spring flowering. Sweet peas need cold temperatures for a good start and they like cold nights, too. Sweet peas do best when direct seeded in the garden in prepared soil. Give them deep, rich, loamy, moist but well-drained soil. Add plenty of organic matter (compost, well-rotted manure, leaf mold, or humus) to enrich the soil. Ensure they have a site with sun to partial sun.
Thank you for this service and for a great website with lots of wonderful flower information. For 6 weeks, I have nursed along many sweet pea seedlings in my Iowa (z5) location and was planning to plant them outside in mid-March. Last week, I started hardening them off on my screened porch for increasing hours each day while watching the weather and temps for the week ahead. Thinking I was going to plant them out tomorrow, two nights ago, I covered them with blankets on my porch all night long, but it was very cold (12 degrees). I thought they had been hardened and were covered properly, but the dirt in their peat pots was frozen hard the next morning. Now, two days later, they seem very limp and there is some yellowing on the edges of the leaves. Do you think I froze them to death, or do you think they will spring back as it gets warmer? Thanks in advance.
Only time will tell. Sweet peas are fairly tolerant to mild frost. I’m guessing it will depend on the health of the seedling as to whether it can bounce back. If the roots are still OK, then the plant might be able to re-grow. If the transplants are of enough size, you might pinch off any blackened leaves/stems. Otherwise, you might just give them extra protection and care, providing as ideal growing conditions as you can, then see if they perk up again. It may take a little time, though, for them to fully recover. Good luck!
The very best ever seen and complete help on article, my grandfather raised them always in Maine and I moved to Washington state awhile ago and saw some growing near the
salt wter and bushy so brought them home and nothing happened for 2 years and finally this year they came up in all
their glory and beautiful purple and red and strong, very much
so in the branches and climbed about 3 feet and strongly bushed out and bloomed all summer. if i cut them back will
they not climb again from roots? One of your articles said to
cut them back i believe but save the root? Have relied on
the Old Farmers all!!! my 87 years!!! Keep up the
fabulous work. Thank you
