Starting Sweet Peas from Seed

Sweet Pea Seeds

Question: Do you have any tips for starting sweet peas from seed indoors?
Answer: Where winters are warm, sow seeds indoors in late January. (Next year, plan to sow the seeds directly in the garden in the fall; they will sprout and root over the winter and bloom earlier in spring.) Where winters are cold, sweet peas should be sown indoors about 6 weeks before your expected last frost date. (Read Alaska gardener Les Brake’s advice on sweet peas.) In all areas, transplants can go outdoors as soon as the soil can be worked. Sweet peas will survive light frosts. Most prefer cool temperatures, though some are moderately heat resistant, such as the heirloom species Lathyrus matucana. Most sweet peas bloom in spring, which is why you want to get them out in the garden as soon as possible. The species Lathyrus belinensis is a later bloomer, with unusual coloring.

To sow sweet peas indoors in pots:

Nick the seed coat with a sharp knife, making a small incision in the hard outer shell. This will make the seed sprout quicker.

Fill four-inch plastic pots or degradable pots (peat pots, Cowpots, pots made of newspaper) with fresh seed-starting mix and dampen it thoroughly. Make a 1-inch-deep hole with your finger, a dibber, a pencil or something similar and insert 1 to 3 seeds. Cover with more mix.

Keep the soil mix moist and at a temperature between 55 and 70˚F.

If more than one seed sprouts, snip the other seedling(s) off at the soil line to leave just one seedling per pot. Grow the seedlings in a bright spot, such as near a south-facing window or on a light stand. If you use artificial lights, the top of the seedlings should stay 6 inches from the bulbs.

When seedlings have 4 pairs of leaves, pinch or cut them off just above the third set of leaves. This will encourage the plant to branch out, making a bushier shape.

To transplant seedlings outdoors, first harden them off by gradually moving them into the open air and sunlight, leaving them out a little longer each day over the course of a week or so. Plant them in rich, well-draining soil. Try not to disturb their roots when you transplant them; slide the root ball out of the pot by squeezing the pot’s walls, and handle them by their leaves and by holding the entire root ball in your palm. If you used peat pots or the like, you can just plant the whole pot in the ground.

Space seedlings 6 inches apart, and bury them to the same depth as they were growing in their pots. Water gently, using a watering can with a rosehead. Sweet peas are climbing flowering annuals. Provide a support for your sweet peas to grow upon, such as a lattice or a framework of twine, or netting with holes at least 2 inches square.

Image credit: Forest & Kim Starr

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See Clarington Forge’s planting dibber, a great tool for planting seeds or transplanting seedlings.

Check out the CobraHead, a versatile tool that’s great for transplanting and more.

Read about familiar and less common annuals, plus seed-starting and transplanting techniques, in Horticulture’s Annuals CD.

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9 thoughts on “Starting Sweet Peas from Seed

  1. I save toilet roll cores, and plant sweet peas seeds in them after soaking 24 hours. Peas don’t like root disturbance, so I plant intact when the plants are about 8″ high. (I do pinch out top shoots) Depending on the season, can usually have flowers from spring right through.

  2. i received absolutely the best tip for starting sweet peas! you put the seeds between two paper towels and lay them in a collander. keep them moist by running water over the paper towels several times a day. when they sprout, plant them. this is usually 5-7 days. since following this advice i have had fabulous luck with my sweet peas. you only plant the seeds that sprout so you don;t have gaps in you rows and they all come up! you can plant them outdoors or in pots in your house until you are ready to transplant. try it. it’s wonderful.

  3. When in the fall can seed be sown directly into the garden? I live in zone 7 Atlanta. I usually buy transplants in the fall or early spring, but the standard snaps are hard to find. Thanks

  4. Meghan says to nick the seeds with a sharp knife before planting. Other articles I have read (Les Brake’s for example) say to soak the seeds. Is one method any better than the other? Thanks!

    • Louann, I just soak seeds overnight; no risk of “nicking” your fingers while trying to hold a small seed while attacking with a sharp knife.
      Soaking is the easy method for any number of seeds that require scarification.

    • I live in zone 5, and I’ve had better luck keeping sweet peas out of strong afternoon sun and heat. A site with morning sun and cooler soil seems to work best; very much like clematis.

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