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

Hi, Evangeline, Thank you for your kind words. Sweet peas are annuals; you should not expect them to last into another season.
We do not know what took these so long to flourish, but it sounds like they were lovely. Perhaps you can get a similar seed next season. Note that these were the vining type; there is also a bush type that will not spread the same way.

Thanks again for all of your enthusiasm. We hope this answers your question.

Abdi rahman (not verified)

8 years 1 month ago

iam very happy

nora (not verified)

8 years 3 months ago

i grew sweet peas, backyard, they need a fence or trellis to climb, tendrils hold the vines up, delicate blooms spread a subtle perfume

Sara-Anne Peterson (not verified)

8 years 4 months ago

I live in the Northwest Territories of Canada. My sweet peas are up and have gorgeous flowers but there is no fragrance. We have had cold and continuous rainy weather. Too much rain?

Some varieties are more fragrant than others (typically, the larger the flower, the milder the fragrance). Heirloom and Heritage varieties tend to be the most fragrant. You may have a variety that is genetically light in fragrance.

Mark Wallin (not verified)

8 years 5 months ago

I moved into my home last June ,now my Sweet Peas are out again for the second time and I love them .Their sent is wonderful. I wonder if I can harvest the pods and take out the seeds and plant them for in house till next years planting out side and as gifts. Any ideas, thanks . Mark

If you are able to dry your seeds and store them properly (don’t plant them), you have a good shot at growing new plants with them next year. To store the seeds: Place them in an airtight, watertight container such as a jar with a rubber seal or a Ziplock bag inside a jar. Keep the seeds cool (ideally, below 50°F); you could also put them in a jar and store them in your refrigerator or freezer. Then, in the early spring, start them inside.

Yasmine (not verified)

8 years 5 months ago

I was determined to grow a sweet pea but the weather in Washignton DC is so extreme that it has been difficult to get a plant to bloom. This year on Feb 1, 2016 I planted Little Sweethearts, a petite variety that is supposed to grow bushy.
I began them indoors: after soaking the seeds overnight, 1 set was planted directly into a 6inch by 6 inch container, and others in little starter cans that would later be transplanted to larger containers once the weather warmed up. February was cold; the seedlings emerged within a week, germinating nicely but remained indoors for the month. In March I gradually moved everything outside, occasionally bringing the plants back indoors if the weather got too cold.
I was plagued by little soil gnats, and no amount of using Natria or Neem oil pest control could get rid of them. I even tried putting garlic on the soil hoping the smell would drive them away, but to no avail.
We had a few stellar days in April, but May was unusually cool for this area. And I think that helped the plants. In late April-May I began adding a few drops of liquid fertilizer when watering. Unfortunately all the transplanted seedlings gradually died off - I think the shock was too much for them. It was so disappointing to see that even though they appeared to initially thrive, they just dried up bit by bit.
However,the plant that had been started off in the 6by6 container which had not been transplanted, did really well. I watched with bated breath as miniature buds formed - one has already dropped, but the other swelled up, and grew ... and bloomed into a marvelous pink little flower. It was miraculous to watch it go from a hairy little green bud, to a little off-white looking emergence, and then hints of pink which finally deepened into a spectacular flower on June 12th. It took a full 4 months and 2 weeks for this to happen. The flower does not seem to have any scent but is lovely nonetheless.
I still have a handful of soil gnats, but I think with the weather warming up they are gradually disappearing. In the meantime, the plant seems to have a few other small buds debating on whether to grow...I am hoping the temperatures stay lower than normal for this region (it has been in the low 80s in June thus far).
It is such a treat to have my morning coffee, and taking in this spectacular beauty. It's a great way to start the day before the chaos of work sets in.

Ann Jordan-Mills (not verified)

8 years 5 months ago

I grow sweet peas wherever I live. I am now in Victoria, BC, Canada. I am thrilled to have picked my first bouquet today, and more are blooming to follow. There are lots of flowers coming, and they are growing higher. They are my every year favourites!

I am a bit concerned about keeping the roots cool, as there is not much shade where they are growing against the house, and some bottom leaves are turning yellow. Is this yellow caused by dryness or heat or what else could it be?

I don't want them to die back, as they are doing so well, and I love them. I am planning to add mulch, and maybe more soil asap.

What do you suggest so that the yellow leaves don't get any worse?
Thank you.

Hi Ann,

Over-watering can lead to root rot and yellow leaves. It may also be lack of magnesium in the soil. To cool the roots you can put some ice cubes in a few small pots with holes in the bottom and place them around the sweet peas.