How to Grow Sweet Peas: The Complete Sweet Pea Flower Guide

Photo Credit
Moravska/Shutterstock
Botanical Name
Lathyrus odoratus
Plant Type
Flower
Sun Exposure
Full Sun
Soil pH
Alkaline/Basic
Bloom Time
Summer
Fall
Flower Color
Blue
Pink
Purple
Red
White
Yellow

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Planting, Growing, and Caring for Sweet Peas

Catherine Boeckmann

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. 

sweet pea flower petals, pink and purple

Read Next

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.
Easy-to-handle sweet pea seeds.
Easy-to-handle sweet pea seeds.

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.

a sweet pea seedling

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.

planting sweet peas near supports

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.

sweet pea flowers in the garden

Types

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

  • In their native Sicily, these ornamental peas have weak stems and an intense orange-jasmine-honey scent. Modern hybrids are stronger-stalked and have larger blooms.
  • At the same time, some of these modern varieties with larger flowers and contemporary hues lack the fragrance of the earlier sweet peas. Sweet pea ‘Cܱ貹Ծ,’ with its bi-colored flowers, maroon upper petals with violet “wings,” is still deservedly popular and is easy to grow.
  • The deliciously-scented ‘A’ is an heirloom, dating to 1896. Its petals unfurl to show stunning wavy red and white stripes.
  • Look for heirlooms like the ‘Old Spice’ collection from Sicily. This strain blooms in shades of white, cream, pink, lavender, and purple.
  • ‘April in Paris’ is a fragrant modern variety with large creamy-yellow blossoms and lilac shading.
  • While the common sweet pea is an annual, there is also a perennial unscented broad-leaved everlasting pea, Lathyrus latiflolius. These clambering plants can reach up to 6 or 7 feet and are hardy to zone 5; they are low-maintenance plants that flower regularly year on year.
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Wit and Wisdom

  • The sweet pea is an essential member of a late-Victorian garden. Victorians loved sweet peas for their color diversity and fragrance.
  • Gather the flowers in the morning when the dew is still on them. This is when their scent is the sweetest.
  • Sweet peas are one of the April birth flowers.

“The odor of the sweet pea is so offensive to flies that it will drive them out of a sick room, though not in the slightest degree disagreeable to the patient.”
–A tip from The 1899 Old Farmer’s 

Here are sweet peas, on tip-toe for a flight:
With wings of gentle flush o’er delicate white,
And taper fingers catching at all things,
To bind them all about with tiny rings.
–John Keats (1795–1821), excerpt from “I Stood Tip-Toe Upon a Little Hill”

Pests/Diseases

Flowers
About The Author

Catherine Boeckmann

Catherine Boeckmann loves nature, stargazing, and gardening so it’s not surprising that she and The Old Farmer’s found each other. She leads digital content for the website, and is also a certified master gardener in the state of Indiana. Read More from Catherine Boeckmann
 

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Comments

Cheryl (not verified)

8 years 6 months ago

How many hours of sun does sweet peas need? I have been planting them where they only get about 3 hours worth of direct sun in the later afternoon.

Susie (not verified)

8 years 9 months ago

I live in San Diego, planted sweet peas in mid December. Plants are doing great but no flowers

Sweet peas can take 3 months from planting to bloom. If your plants are healthy you should see blooms before long. You can feed them with a fertilizer that is high in phosphorous to promote more flowers.

Hello, I am in San Diego too. I just sow the sweet pea seeds today in the small pot and I forgot soaking them. Do you think it's ok or I need to undo to soak them? Please help, thanks so much.

Bonnie (not verified)

8 years 10 months ago

I live in South Louisiana. Am I too late in planting my seeds, now?

I’m afraid so. In your region, plant sweet peas in October or November and provide a good trellis. They’ll bloom in February or March and continue into May.

mamagoody1 (not verified)

8 years 12 months ago

I live in NE Ohio. My husband planted sweet peas earlier in the year. From what I am reading here, I think we probably planted them too late. They never bloomed, in fact, the didn't even grow very well until very late summer. It is now the end of November, we have had several hard frosts, and they are still green and bushy. My question is.... is there any chance that they will come up in the spring? As I said, they did not bloom, so it won't be a matter of them re-seeding, but could they grow back in the spring? If they could, should we leave them alone, or cut them back? Thanks for the information!!!

Sweet peas need to be protected from hard freezes and heavy snows. If the ground is still soft you can dig up the plants and plant them in a big container. Move the container into an unheated garage or shed and cover with some blankets if the outside temps. drop below 20 degrees. Do not prune the plants. Most people regard sweet peas as annuals and plant new seeds every year. The trick is to get the seeds growing early in the spring. You can start them indoors 6 to 8 weeks before your last spring frost and then get the seedlings outdoors as soon as possible.

Domenico (not verified)

9 years ago

Any tips for flower abortion?