Growing sweet peas in USDA Zone 10 means gardening with a mild winter and only a rare frost. Sweet peas are cool-season climbers grown for their scented flowers, and Zone 10's mild winter is one of the best climates in the country for them. They flower best when plants grow through cool weather, then fade fast once summer heat arrives. This guide covers when to plant sweet peas in Zone 10, with the soil, spacing, sun, water and care it needs. Use the Zone 10 planting calendar to see what else to sow alongside it.
Zone 10 at a glance
USDA Zone 10 has average winter lows of 30 to 40°F, a last frost around Jan 15–30 and a first frost around Dec 15–31 — and frost is rare in much of the zone. Plan around those averages, not the calendar: a cold night or a warm spell can shift everything by a week or two, so check your local extension service for your area. Sweet Peas are cool-season flowers here, grown through autumn, winter and spring rather than through summer heat.
| Detail | Zone 10 guidance |
|---|---|
| Average last spring frost | Jan 15–30 (average/range, frost rare) |
| Average first autumn frost | Dec 15–31 (average/range, frost rare) |
| Days to germination | 7–14 days |
| Days to maturity | 60–70 days |
| Sowing | Direct sow in autumn (October–November) |
| Transplanting / planting out | After the average last frost (Jan 15–30), or autumn-sown plants flower from late winter |
| Harvest | Flowers 60–70 days after sowing; pick regularly to keep plants flowering |
| Sun | full sun |
| Soil pH | 6.0–7.5 |
| Spacing | 6–8 inches |
| Water needs | moderate |
When to plant sweet peas in Zone 10
Sow sweet peas in autumn, in October and November, so plants establish through the mild winter and flower from late winter into spring. A second sowing in January can stretch the season, but autumn-sown plants are always the strongest because they build deep roots before flowering. Sweet peas take 60–70 days to maturity, so an October sowing is in flower by late winter. Because frost is rare in Zone 10, with an average last frost of Jan 15–30 and a first frost of Dec 15–31, plants sown in autumn rarely need protection — but keep fleece handy for the odd cold night. If you are unsure of your own dates, the seed-starting calculator will help you work the timing out. Frost dates are zone averages — check your local extension service before you commit to a date.
Starting sweet peas in Zone 10
Sweet peas are direct sown, and they dislike being transplanted, so sow where they are to flower. Soak the seed overnight in water before sowing to speed germination, then sow about an inch deep in a drill or in pots of compost that you will plant out whole. Seeds germinate in 7–14 days. Put the support in place at sowing time — a trellis, netting or a wigwam of canes — because the tendrils need something to grip from the moment they appear, and adding supports later damages roots.
Soil, spacing, sun and water
Sweet peas want rich, moisture-holding soil, so dig in well-rotted compost or garden compost before sowing, and mulch once plants are growing. They like a pH of 6.0–7.5 and full sun, with their roots kept cool and shaded by mulch or low planting around the base. Space plants 6–8 inches apart along the support. Sweet peas need moderate water, kept even rather than feast-and-famine. Water at the base in the morning, keep the soil moist while plants are flowering, and mulch to hold moisture in — dry roots in a warm spell will cut flowering short.
Companion planting
Good companions for sweet peas include lavender, marigolds, garlic, chives. The companion planting finder can suggest combinations for your whole bed. Do not plant sweet peas where peas or beans grew last year, and keep them away from onions and garlic, which can stunt legumes. Good companions include lavender, marigolds, garlic and chives.
Pests and problems
The common pests and problems to watch for with sweet peas are aphids, bean beetles, slugs, cutworms. Aphids cluster on the soft shoot tips and young buds, and are the pest to watch first — wash them off with a strong jet of water before they build up. Slugs take young seedlings on damp nights, cutworms can sever stems at soil level, and bean beetles chew the leaves. Check plants regularly, protect seedlings with a ring of grit or a cloche, and remove badly affected shoots rather than waiting for the problem to spread.
Harvest and storage
Pick sweet pea flowers little and often, cutting the stems when the flowers are fully open. The more you pick, the more the plant produces, while flowers left to set seed will shut flowering down. Cut in the cool of the morning and stand stems in water straight away. Sweet peas are grown for cut flowers, not for eating — the seeds are not edible, so do not confuse them with garden peas. Cut stems keep for several days in a vase of cool water if you change the water daily and keep the vase out of direct sun.
Making the most of Zone 10
Zone 10's advantage is a winter growing season that most of the country cannot use: autumn sowing gives you flowers in late winter and spring, when the rest of the garden is still waking up. The challenge is the turn to summer heat, so enjoy the peak, keep picking, and let the plants finish as temperatures rise. Related reading: Calendula in Zone 10 and October in Zone 10. Also see November in Zone 10 for what else to sow alongside it.
Frequently asked questions
When should I plant sweet peas in Zone 10?
Sow sweet peas in autumn, in October and November, so plants establish through the mild winter and flower from late winter into spring. Check your local extension service — these are zone averages, not exact dates for your garden.
How long do sweet peas take to grow in Zone 10?
Seeds germinate in 7–14 days, and the crop takes 60–70 days to maturity. In Zone 10, allow the longer end of the range if conditions are cool or dry at sowing time.
Are sweet peas edible?
No. Sweet peas are ornamental flowers and their seeds are not edible, so grow them for scent and cutting only, and do not confuse them with garden peas, which are a different plant.
What soil and spacing do sweet peas need in Zone 10?
Sweet Peas need full sun and soil pH 6.0–7.5, spaced 6–8 inches apart. Dig in well-rotted compost, water deeply, mulch, and test your soil through your local extension service.