How to Grow Sweet Peas from Seed, Step by Step

Here is how to grow sweet peas: sow the seeds in autumn or late winter into deep pots or straight into rich soil, pinch out the tips of young plants, give the vines a sturdy support to climb and pick the flowers often. Do that and you will have fragrant blooms from late spring until the heat of summer.

Sweet peas are cool-season climbers, so timing matters more than anything. They love cool roots, plenty of water and regular picking. Here is the full process, from seed to vase.

Pink sweet pea flowers, how to grow sweet peas for fragrant blooms

Quick Answer: Growing Sweet Peas at a Glance

Sow: October to November (mild winters, UK) or February to April; very early spring in cold areas.
Light: full sun, at least 6 hours.
Soil: rich, deep, well-drained, with compost worked in.
Support: trellis, netting or cane wigwam 6 feet (1.8 m) tall.
Key habit: pick often and never let pods form.

When to Sow Sweet Pea Seeds

Sweet peas dislike hot weather, so the aim is to get plants established while it is still cool. Check your zone on the USDA Plant Hardiness Zone Map to match the table below.

Climate	Best sowing time	Where
Cold winters (zones 3 to 5)	Late winter to early spring	Indoors, then plant out or direct sow as soon as soil thaws
Moderate (zones 6 to 7)	Fall or late winter	Cold frame or direct sow in early spring
Mild winters (zones 8 to 9)	October to January	Directly in the ground
UK	October to November, or February to March	Deep pots in a cold greenhouse or frame

How to Grow Sweet Peas from Seed Step by Step

Soak seeds in water overnight, or nick the hard coat with a nail file, to speed germination.
Sow one to two seeds per deep pot (such as a root trainer or paper tube), about 1/2 to 1 inch (1 to 2.5 cm) deep.
Keep in a cool, bright place, ideally 50 to 60°F (10 to 15°C). Seeds usually sprout in 10 to 21 days.
When seedlings have three pairs of leaves, pinch out the growing tip to encourage side shoots.
Harden off, then plant out in spring about 6 to 8 inches (15 to 20 cm) apart at the base of a support.
Tie in new shoots early on, then the tendrils will take over. Mulch to keep roots cool.

Bright sweet peas cut and arranged in a glass vase

Caring for Sweet Peas

Water deeply and regularly, especially once buds form. Feed every two weeks with a high-potash fertilizer, such as tomato feed, once flowers start. Pick every few days: cut stems when two or three flowers are open. If seed pods form, the plant thinks its job is done and stops flowering. Dead-head any flowers you do not pick. If your garden has deer, our guide to the best deer repellents will help protect young plants.

Looking for similar easy climbers and companions? See nasturtium plants and when to plant wildflower seeds.

Sweet Pea Types Compared

Type	Height	Scent	Best for
Spencer (grandiflora)	5 to 7 feet	Moderate to strong	Cut flowers
Old-fashioned (Grandiflora)	4 to 6 feet	Very strong	Fragrance
Dwarf / bush	1 to 3 feet	Light to moderate	Pots and edges

Common Sweet Pea Problems and Fixes

Few flowers: not enough picking, heat or too much nitrogen. Pick often and switch to potash feed.
Buds dropping: dry roots or sudden temperature swings. Water consistently and mulch.
White powder on leaves: powdery mildew. Improve airflow and water at the base.
Aphids: spray with water or use insecticidal soap.
Seeds not sprouting: rot from soggy compost or mice. Use well-drained mix and keep pots covered from rodents.

Are Sweet Peas Safe for Pets?

Garden sweet peas (Lathyrus odoratus) are ornamental plants whose seeds and pods are not meant to be eaten and are not edible like culinary peas. The ASPCA toxic plants list includes them as toxic to pets, so keep them out of reach.

Conclusion

Sweet peas reward a little planning: sow at the right time, give deep roots room, pinch and support the vines, and pick constantly. A single clump near the kitchen door will scent a whole room when you bring the stems inside.