Nasturtiums are the cheerful workhorses of a Zone 9 garden: bright, peppery flowers that bloom for months, leaves and flowers you can eat, and a habit of attracting aphids away from your vegetables — they are a trap crop as well as a flower. They grow fast from seed, need almost nothing, and will tumble over a wall, climb a fence or fill a pot with equal enthusiasm.
In Zone 9, nasturtiums are at their best in the cool months. They love mild weather and sulk in high summer heat, so the smart Zone 9 timing is autumn and late winter sowings, not a midsummer one.
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 | 50–60 days |
| Sowing | direct sow |
| Sun | full sun |
| Soil pH | 6.0–7.5 |
| Spacing | 8–12 inches |
| Water needs | moderate |
| Cold tolerance | tender |
When to plant nasturtiums in Zone 9
Sow nasturtiums in Zone 9 in autumn, from September through November, and again in late winter, from February through March, for flowers through the cool months. Seeds germinate in 7–14 days and plants flower in 50–60 days, so an October sowing is blooming by December, and a February sowing flowers by April. 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. Nasturtiums are tender and a frost will damage them, but they are quick to regrow, and a light frost in Zone 9 rarely kills an established plant outright. Avoid sowing in June, July and August: the heat makes them leggy, short of flowers and quick to finish.
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 nasturtiums in Zone 9
Direct-sow nasturtiums where they are to grow — they dislike root disturbance and transplant badly. Soak the large seeds overnight in water to speed germination, then sow them an inch deep in their final position. Seedlings appear in 7–14 days; thin them to 8–12 inches apart once they are big enough to handle. Give climbing types a fence, trellis or wall to scramble up, and let trailing types spill over the edge of a raised bed or pot.
See also when to plant nasturtiums in Zone 8 for the same crop in a cooler zone.
Soil, spacing, sun and water
Nasturtiums need full sun and poor to average, well-drained soil with a pH of 6.0–7.5. Like cosmos, they flower worst in rich soil: too much compost or fertiliser produces a mass of leaves and almost no flowers, so skip the feeding and let them struggle a little. Space plants 8–12 inches apart so air can move between them. Water needs are moderate: water young plants until established, then water in dry spells only — established nasturtiums are fairly drought-tolerant. Water at the base in the morning. The seed spacing calculator can help you plan the bed before you plant.
Companion planting
Good companions for nasturtiums include lavender, marigolds, garlic and chives, but their real value is as a companion themselves: nasturtiums are a classic trap crop, attracting aphids away from beans, brassicas and tomatoes, and their flowers bring bees and hoverflies into the garden. Plant them at the ends of vegetable beds and around fruit trees. Cosmos are another easy Zone 9 annual that shares the same sunny, undemanding character, and our guide to when to plant cosmos in Zone 9 shows how the two can fill a border together. The companion planting finder can suggest combinations for your whole bed.
Pests and problems
The common pests to watch for with nasturtiums are aphids, slugs and cutworms — and with nasturtiums, aphids are partly the point: the plants draw aphids away from your vegetables, so a colony on a nasturtium is doing its job. If the colony gets very heavy, wash it off with a strong jet of water. 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
Nasturtiums take 50–60 days to maturity from sowing, flowering from late autumn through spring in Zone 9. Pick the flowers and young leaves for salads as soon as plants are big enough — both are edible, with a peppery, watercress-like bite. Pick in the morning, when the leaves are cool and crisp, and use them the same day. Deadhead spent flowers if you want more blooms, or let the plants set seed: the round green seed pods can be pickled like capers, and seed left to ripen will self-sow for next season.
Frequently asked questions
When should I plant nasturtiums in Zone 9?
Sow in autumn (September–November) and again in late winter (February–March). Seeds germinate in 7–14 days and plants flower in 50–60 days. Avoid sowing in midsummer — heat makes them leggy and short of flowers.
Are nasturtiums edible?
Yes — the flowers and young leaves are edible, with a peppery taste like watercress. Pick them in the morning and use them the same day in salads. The green seed pods can be pickled like capers.
Do nasturtiums attract aphids?
Yes — deliberately. Nasturtiums are a trap crop: aphids prefer them to your vegetables, so plant nasturtiums near beans, brassicas and tomatoes to draw aphids away from the crop.