Sweet peas are the most fragrant flower you can grow from seed: a wigwam of them in full flower perfumes the whole garden on a summer evening, and a bunch of sweet peas on the kitchen table is one of the great pleasures of summer. They are also one of the best cut flowers, because the more you pick them, the more they flower.
Sweet peas are hardy annuals, which means they are sown in autumn in mild zones or in early spring in cold ones, and they flower best in cool weather — they fade in real heat. They climb by tendrils, so they need something to climb on: a wigwam of canes, a trellis, a fence or netting. Give them rich soil, plenty of water and something to climb, and they will flower for months.
Sweet Peas at a glance
| Growing factor | What sweet peas need |
|---|---|
| Sun | full sun |
| Soil pH | 6.0–7.5 |
| Days to germination | 7–14 |
| Days to maturity | 60–70 |
| Spacing | 6–8 inches apart |
| Water needs | moderate |
| Cold tolerance | hardy |
| Family | Fabaceae |
Starting seeds
Sweet Peas are direct-sown where they are to grow — they dislike transplanting, so skip the seed trays. Sow after the last frost, when the soil has warmed: in Zones 3–5 that is late spring, in Zones 6–8 mid-spring, and in Zones 9–10 early spring, with a second sowing possible in late summer. Zones 11–13 are frost-free, so you can sow in succession through much of the year; check your local extension service for the best local sowing dates. Seeds germinate in 7–14 days in warm, moist soil. Sow at the spacing in the at-a-glance table above rather than thickly and then thinning hard — although thinning is still needed if germination is patchy, sow thinly to start. Cover lightly, keep the soil evenly moist until seedlings appear, and mark the row so you do not weed out the seedlings by mistake. Our seed starting calculator and germination time calculator help you plan sowing dates, and the seed spacing calculator works out row spacing.
Transplanting and planting out
Sweet Peas are sown where they grow, so there is no transplanting step — instead, thin the seedlings once they are a few inches tall, leaving the strongest one at each 6–8-inch spacing. Thin on a damp day, water the row first so the remaining seedlings are not disturbed, and snip out the extras rather than pulling them, which can damage the roots of the ones you keep. Our plant spacing calculator works out exactly how many plants fit your bed, and the square foot garden planner helps lay them out.
Soil and feeding
Sweet Peas grow best in fertile, well-drained soil with a pH of 6.0–7.5. Dig in compost before planting — it feeds the soil and helps it hold moisture without getting soggy — and mulch after planting to keep the roots cool and the weeds down. Feed during the growing season with a balanced fertiliser at the label rate, roughly once a month while plants are actively growing, and stop feeding as the season ends. Our fertiliser calculator works out the right amount for your bed, and the compost ratio calculator helps you make good compost to dig in.
Watering
Sweet Peas have moderate water needs: keep the soil evenly moist while plants are establishing and flowering, and water deeply rather than little and often so the roots grow down. Water at the base in the morning so the foliage dries during the day, mulch to hold moisture in, and watch for wilting in hot, dry spells. Our watering calculator gives a starting point for your bed size, and the watering schedule generator can build a routine around it.
Sunlight and temperature
Sweet Peas need full sun — at least six hours of direct sun a day. Sweet Peas are hardy and tolerate frost and cold weather well, so they can be planted out earlier and left in the ground over winter in most zones. In frost-free Zones 11–13, heat and a lack of winter chill can limit performance, so give them the coolest spot you have. Check your zone with the hardiness zone finder before choosing varieties. Our sunlight calculator can check whether your spot gets enough sun.
Pests and diseases
The pests and diseases to watch for on sweet peas are aphids, bean beetles, slugs, cutworms. Aphids cluster on shoot tips, bean beetles can chew the leaves, and slugs eat young seedlings. Cutworms may cut young plants at the base, so protect seedlings with a collar. Check plants weekly, looking under leaves as well as on top, and act early. Hand-pick larger pests, knock aphids off with a strong spray of water, and remove badly affected leaves. Keep the area weed-free and avoid wetting the foliage when you water, since damp leaves invite fungal disease. Our pest identifier helper can help identify what you are seeing, and the plant disease checker helps narrow down leaf and stem problems.
Companion plants
Good companions for sweet peas are lavender, marigolds, garlic, chives. Lavender, marigolds, garlic and chives are good companions, and sweet peas also grow well near other climbers, where they share a support without competing much. Our companion planting finder can suggest more pairings for your bed plan.
Harvesting
Pick sweet peas every day once they start flowering — cut the stems long, in the morning, and put them straight into water. Regular picking is the whole secret: a sweet pea left to set seed stops flowering, while a sweet pea picked daily keeps producing new blooms for weeks. Never let seed pods form on the plant if you want flowers, and do not eat sweet peas — unlike garden peas, the seeds are toxic. Our harvest date calculator can estimate your picking date from your sowing date, and the vegetable yield estimator helps you work out how much a bed will produce.
Common problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| Plants stop flowering in summer | heat, or seed pods left on the plant | Pick daily, remove seed pods, and water well in hot weather. |
| Seedlings cut at the base | cutworms | Protect seedlings with a collar and sow a few extra. |
| Powdery mildew in late summer | damp leaves and poor air flow | Water at the base and remove affected leaves. |
Plants stop flowering in summer
Sweet peas are cool-weather plants, and they stop flowering when it gets hot, or when seed pods are left on the plant. Pick every day, snip off any pods that form, and water deeply in hot spells to keep them going as long as possible.
Seedlings cut at the base
Cutworms cut young sweet pea seedlings clean through at soil level, usually at night. Use a cardboard collar around each seedling, and check the soil around a damaged plant — the caterpillar is usually curled up just below the surface.
Powdery mildew in late summer
In late summer, sweet pea leaves often develop white powdery mildew, especially in still, damp air. Water at the base in the morning, keep the plants well spaced for air flow, and remove the worst leaves. It rarely kills the plant, but it does shorten the flowering season.
Frequently asked questions
How long does it take to grow sweet peas?
From planting to maturity takes 60–70 days. Seed germination takes 7–14 days, and the total time depends on whether you start from seed, a nursery plant, or a bulb or cutting.
How far apart should I plant sweet peas?
Space sweet peas 6–8 inches apart. That spacing gives each plant room for air movement, which keeps disease down, and room to reach its full size without crowding its neighbours.
What soil pH do sweet peas need?
Sweet Peas prefer a soil pH of 6.0–7.5. Test your soil before amending it — most garden soils are close enough, and guessing with lime or sulphur can do more harm than good.
Can you eat sweet peas?
No. Sweet pea flowers and seeds are toxic if eaten, unlike garden peas. Grow them for their scent and flowers only, and keep seed pods away from children.
Do sweet peas need support?
Yes. Sweet peas are climbers and need canes, netting, a trellis or a fence to climb. Without support they sprawl on the ground, flower poorly and are far more likely to be eaten by slugs.