Sweet peas are the most fragrant flowers you can grow in Zone 9 — a single bunch picked in the morning will scent a whole room. They are a cool-season annual, and in Zone 9 that means one thing: sow them in autumn, let them grow through the mild winter, and enjoy a long spring flowering before the heat arrives.
Sweet peas are not a summer flower in Zone 9, and gardeners who sow them in spring are often disappointed: the plants grow, but the heat ends flowering early. An autumn sowing is the secret.
Zone 9 at a glance
USDA Zone 9 covers the warmest parts of the southern United States, including much of Florida, southern Texas, southern Louisiana, southern Arizona and coastal California. Winters are mild, with average winter lows of 20 to 30°F, and the growing season runs nearly all year.
The average last spring frost is Jan 30–Feb 15 and the average first autumn frost is Dec 1–15 — USDA/NOAA averages, not exact dates, so check your local extension service before planting.
| Detail | Zone 9 guidance |
|---|---|
| Average winter low | 20 to 30°F |
| Average last spring frost | Jan 30–Feb 15 (average/range) |
| Average first autumn frost | Dec 1–15 (average/range) |
| Days to germination | 7–14 days |
| Days to maturity | 60–70 days |
| Sowing | direct sow |
| Sun | full sun |
| Soil pH | 6.0–7.5 |
| Spacing | 6–8 inches |
| Water needs | moderate |
| Cold tolerance | hardy |
When to plant sweet peas in Zone 9
Sow sweet peas in Zone 9 in autumn, from October through November, for the best display, with a second sowing in late winter, from January through February, as a backup. Seeds germinate in 7–14 days and plants flower in 60–70 days from spring growth, so an autumn sowing blooms from March onwards and keeps going until the heat of late spring. The average last spring frost in Zone 9 is Jan 30–Feb 15 and the average first autumn frost is Dec 1–15 — those are USDA zone averages, not exact dates for any one garden, so always check your local extension service for your own frost dates. Sweet peas are hardy and tolerate light frost, which is exactly why the autumn sowing works so well in Zone 9: the plants sit through winter, growing slowly, and burst into growth in spring.
Work back from the frost dates: the planting calendar hub and the October in Zone 9 month guide show what else is happening at planting time.
Starting sweet peas in Zone 9
Direct-sow sweet peas where they are to grow, or start them in deep pots — sweet peas make long roots and dislike disturbance, so use root trainers or deep pots if you start them indoors. Soak the seeds overnight, or nick the hard seed coat with a knife, to speed germination. Sow seed an inch deep, in a trench or in a circle around a wigwam of canes, and give them a support from the very start: a wigwam, a trellis or a fence. Seedlings appear in 7–14 days; thin or space them 6–8 inches apart. Pinch out the growing tip once plants have two or three pairs of leaves — this makes them branch and produce far more flowers.
See also when to plant sweet peas in Zone 8 for the same crop in a cooler zone.
Soil, spacing, sun and water
Sweet peas need full sun and rich, moisture-holding soil with a pH of 6.0–7.5. Dig in plenty of well-rotted compost before sowing — sweet peas are hungry plants, and a well-fed plant flowers for weeks longer. Space plants 6–8 inches apart along their support. Water needs are moderate: keep the soil evenly moist, especially in spring when plants are growing fast and flowering, and water at the base in the morning. A mulch of compost keeps roots cool, which matters in Zone 9, where warm roots in spring can shorten flowering. The seed spacing calculator can help you plan the bed before you plant.
Companion planting
Good companions for sweet peas include lavender, marigolds, garlic and chives. Low companions at the base of the sweet pea wigwam shade the soil and keep roots cool — marigolds and calendula both suit the spot, and their flowers add colour at ground level while the sweet peas flower overhead. Calendula is another cool-season Zone 9 flower that shares the autumn sowing window, and our guide to when to plant calendula in Zone 9 shows how the two can be timed together. Avoid planting sweet peas where peas or beans grew last year, and rotate the bed each season. The companion planting finder can suggest combinations for your whole bed.
Pests and problems
The common pests to watch for with sweet peas are aphids, bean beetles, slugs and cutworms. Aphids cluster on buds and young shoots — wash them off with a strong jet of water and encourage ladybirds. Bean beetles chew the leaves; hand-pick them and check leaf undersides. Slugs nibble young seedlings, especially after rain; hand-pick them after dark and keep mulch pulled back from the stems. Cutworms can sever young stems at soil level overnight; a cardboard collar around each seedling stops them.
Harvest and storage
Sweet peas take 60–70 days to maturity from spring growth, flowering from March through late spring in Zone 9. Pick the flowers little and often — every day or two in peak season — and the plant will keep producing new buds for weeks. Pick in the morning, when the flowers are cool and the scent is strongest, and stand them in cool water immediately. Never let the plants set seed: a sweet pea that sets pods stops flowering, so deadhead or pick every flower, even ones you do not need. At the end of the season, pull the plants and compost them once the heat finishes them, and sow a fresh batch in autumn.
Frequently asked questions
When should I plant sweet peas in Zone 9?
Sow in autumn, from October through November, for the best display, with a second sowing in January–February as a backup. Seeds germinate in 7–14 days and plants flower in 60–70 days from spring growth.
Why do my sweet peas stop flowering so early?
Usually heat, or plants left to set seed. Sweet peas are a cool-season flower — an autumn sowing flowers far longer than a spring one, and picking every flower (never letting pods form) keeps them blooming for weeks.
Should I pinch out sweet peas?
Yes — pinch out the growing tip once plants have two or three pairs of leaves. It makes them branch and produce far more flowers, and gives you a bushier plant.