Growing sweet peas in USDA Zone 12 needs an honest warning up front: sweet peas are a cool-season flower, and Zone 12 is tropical. With average winter lows of 50 to 60°F and no frost at all, sweet peas will only thrive in the coolest months of the year, and even then they will be short-lived compared with the long, scented display a temperate garden enjoys. Plant them expecting a brief season of fragrance — not a permanent fixture — and you will enjoy them rather than being disappointed.
This guide covers when to plant sweet peas in Zone 12, how to time them for the cool season, and how to get the most from a short window. Sweet peas take 60–70 days to maturity, so timing matters: sow too late and the heat arrives before the flowers do. Use the Zone 12 planting calendar to see what else suits the cool season.
Zone 12 at a glance
USDA Zone 12 has average winter lows of 50 to 60°F and is frost-free year-round — there is no last or first frost date to plan around. Plan by heat and by the wet and dry seasons instead: heat lovers grow year-round, while cool-season crops only succeed in the coolest months. These are zone averages, not promises for any one garden, so check your local extension service for your area.
| Detail | Zone 12 guidance |
|---|---|
| Last / first frost | None — Zone 12 is frost-free year-round |
| Average winter low | 50 to 60°F |
| Days to germination | 7–14 days |
| Days to maturity | 60–70 days |
| Sowing | Direct sow where it is to grow |
| Transplanting / planting out | Year-round (frost-free); best results in the planting window above |
| Harvest | Harvest 60–70 days after sowing/transplanting; pick regularly |
| Sun | full sun |
| Soil pH | 6.0–7.5 |
| Spacing | 6–8 inches |
| Water needs | moderate |
When to plant sweet peas in Zone 12
In Zone 12, sweet peas should be planted only in the coolest months, roughly November to February, when night temperatures are at their lowest. There is no frost to plan around — average winter lows are 50 to 60°F and the zone is frost-free, so there is no last or first frost date — but heat, not frost, is the limiting factor here. A planting made in the hot months will bolt, fade and die quickly. Because sweet peas take 60–70 days to maturity, sow early in the cool season so they flower before the heat returns. Check your local extension service for the best planting windows in your area, and treat sweet peas as a cool-season annual in Zone 12, not a year-round plant.
Starting sweet peas in Zone 12
Sweet peas are direct-sown where they are to grow, because they dislike root disturbance and their seedlings are fragile. Sow the large seeds about an inch deep in cool, moist soil; they germinate in 7–14 days. Soaking the seeds overnight can speed germination, and nicking the seed coat helps too. Give them a trellis, fence or string to climb from the start — sweet peas grow fast once they get going, and a support put in late will damage the roots. Set them in a spot with morning sun and afternoon shade, which buys them extra weeks before the heat arrives.
Soil, spacing, sun and water
Sweet peas want full sun in a cool climate, but in Zone 12 morning sun with afternoon shade is the safer choice, since hot soil shortens the season. They need rich, well-drained soil with a pH of 6.0–7.5, and they like steady moisture without waterlogging — sweet peas are thirsty plants. Space plants 6–8 inches apart along their support, and dig in plenty of compost before sowing, since a plant that flowers this heavily is hungry. Mulch lightly to keep the roots cool, which can extend the flowering season by weeks. The plant spacing calculator will help you work out how many plants fit your support.
Companion planting
Good companions for sweet peas include lavender, marigolds, garlic, chives. In a cool-season bed, sweet peas pair well with other short-season flowers and with leafy greens that enjoy the same mild weather. Marigolds draw pollinators to the bed, while the alliums help confuse pests. As members of the pea family, sweet peas also fix nitrogen in the soil, which benefits whatever follows them in the bed — a useful bonus in a short-season planting.
Pests and problems
The common pests and problems to watch for with sweet peas are aphids, bean beetles, slugs, cutworms. Aphids cluster on shoot tips and buds in mild weather and can be knocked off with water; bean beetles chew leaves and are best hand-picked. Slugs are a year-round problem in a frost-free climate and feed on young sweet pea shoots at night, so protect new sowings. Cutworms can sever young stems at soil level. In Zone 12's warmth, the biggest problem is often not pests but heat itself — wilting, fading flowers and leggy growth are signs the season is ending, not a disease to cure. Note that sweet pea seeds are toxic — do not eat them.
Harvest and storage
Sweet peas flower 60–70 days after sowing, and cutting is the secret to a long season: cut stems regularly for the vase and the plant will keep producing new flowers. Cut in the morning, when the blooms are fresh and scented, and cut deep — a long stem encourages a long replacement shoot. If you let the pods set seed, the plant will stop flowering, so deadhead and cut often. When the heat arrives and plants fade, pull them and replace them with a heat lover such as nasturtiums or zinnias rather than trying to keep them going.
Making the most of Zone 12
Zone 12 gives sweet peas a short window, not a long season — and that is fine, as long as you plant for it. Sow early in the cool season, give them shade and cool roots, support them from the start, and cut often for the vase. Related reading: Nasturtiums in Zone 12 are a heat-loving climber for the months after the sweet peas finish, and January in Zone 12 is the coolest month to plant.
Frequently asked questions
When should I plant sweet peas in Zone 12?
Only in the coolest months, roughly November to February. Zone 12 is frost-free with winter lows of 50 to 60°F, so there is no last or first frost date — heat, not frost, is the limit. Check your local extension service — these are zone averages, not exact dates for your garden.
Can I grow sweet peas all year in Zone 12?
No — sweet peas are a cool-season flower and Zone 12 is tropical. They will fade and die once the heat returns, so treat them as a short cool-season annual and replace them with heat lovers such as nasturtiums.
How long do sweet peas take to grow in Zone 12?
Seeds germinate in 7–14 days, and the plants flower 60–70 days after sowing. Sow early in the cool season so they flower before the heat arrives.
Are sweet peas edible?
No — sweet pea seeds are toxic and should not be eaten. Grow them for their flowers and scent, and keep the seeds away from children and pets.