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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 started sweet peas from seed indoors in March. They are now in 4" pots in my window sill and the vines are 4-6" long. I know it's time for a transplant, but I live in Virginia in zone 7 where I am afraid these sweet peas will not survive the outside heat. I was thinking about trying to keep them indoors until the fall but I will need to find something for them to climb, as they are hanging down the edge of the wall now. Any recommendations on what I can do to keep them going until I can get them into the ground when it's cooler?
Broadly speaking, based on the planting advice above, you would have been safe planting the seeds in the spring, being in Zone 7; of course, micro-climate conditions can put you into a higher zone. But here are a few ideas:
You can transplant them outside in part shade, in well-drained soil (not clay). They like sunshine, but they like cool soil. Organic mulch will help that, but certain mulches can also harbor slugs, especially the coarser materials such as bark mulch or straw. Fine organic matter isn’t as attractive to slugs.
You can also try planting your sweet peas in containers outdoors, using the potting soil etc. that you have. In the heat of the afternoon, provide some shade for them, or wheel them into a shady spot.
Read above about care and pests.
We hope this helps!
I have a sweet pea that I moved about 7 years ago from my aunts home...we put it in a spot "temporaily" until we found a better place for it...and its still there! I live in zone 5...when and how can we transplant to another location..so that we can have it grow up instead of lieing on the the ground...thank you!
Sweet peas love cool weather; it might be getting too hot for them now. If you’d like to try, however, you can transplant them to a part shade area, in well-drained soil (not clay). They like sunshine, but they like cool soil. Organic mulch will help that, but certain mulches can also harbor slugs, especially the coarser materials such as bark mulch or straw. In the heat of the afternoon, they will need shade. Choose your planting site wisely. Good luck!
Is it possible to grow sweet pea in a indoor greenhouse?
Yes, you can start sweet pea seeds indoors in a greenhouse. Here in northern climates, we sow mid-April and grow indoors for 3 to 4 weeks before transplanting outside.
I'm in Washington State. What zone am I? When should I start planting my sweet pea seeds so I can get it in Early or late Spring?
I planted mine in March and now they're about 5 ft tall. It probably bloom will July. Any tricks so I can them sooner?
Washington has quite a range—mostly 6am to 8b. So it depends where in Washington. See the Plant Hardiness Map: http://planthardiness.ars.usda.gov/PHZMWeb/
If you planted by the spring equinox in March, you should probably see blooms by the summer equinox in June.
I believe I am in zone 7, and I would love to plant sweet peas. Sadly, I think it is too late to get them this year, but perhaps next. What variety will produce large pink or purple flowers on long stems for cutting?
If you’re in zone 7 (or south), you could go for fall planting. Sweet Pea-Mammoth is a variety with large flowers on long stems.
