Nasturtiums are the most generous flower in the garden: they germinate in days, grow almost anywhere, and give you months of bright orange, red and yellow flowers, plus leaves and flowers you can eat. They are also the classic trap crop, drawing aphids away from your vegetables and onto themselves.
Nasturtiums are at their best in poor soil, which surprises people: in rich soil they grow huge leaves and few flowers, while in poor, dry soil they flower their hearts out. They trail, climb and sprawl, so they are perfect for hanging baskets, the edges of raised beds, and scrambling up a fence. And the whole plant is edible — the flowers are peppery and the leaves taste like watercress.
Nasturtiums at a glance
| Growing factor | What nasturtiums need |
|---|---|
| Sun | full sun |
| Soil pH | 6.0–7.5 |
| Days to germination | 7–14 |
| Days to maturity | 50–60 |
| Spacing | 8–12 inches apart |
| Water needs | moderate |
| Cold tolerance | tender |
| Family | Tropaeolaceae |
Starting seeds
Nasturtiums 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
Nasturtiums 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 8–12-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
Nasturtiums 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
Nasturtiums 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
Nasturtiums need full sun — at least six hours of direct sun a day. Nasturtiums are tender — frost kills them or damages them badly, so they are grown as warm-season plants in most zones and planted out only once frosts are over. In frost-free Zones 11–13 they can grow for much of the year. Use the frost date calculator to find your last frost date. Our sunlight calculator can check whether your spot gets enough sun.
Pests and diseases
The pests and diseases to watch for on nasturtiums are aphids, slugs, cutworms. Aphids love nasturtiums, which is exactly why they are planted as a trap crop near vegetables — the aphids go to the nasturtiums instead. Slugs can eat seedlings, and cutworms may cut young plants at the base. 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 nasturtiums are lavender, marigolds, garlic, chives. Lavender, marigolds, garlic and chives are good companions, and nasturtiums themselves are the companion other crops want: plant them near brassicas and beans to draw aphids away. Our companion planting finder can suggest more pairings for your bed plan.
Harvesting
Pick nasturtium flowers and leaves for salads from midsummer onwards — both are edible, with a peppery, watercress-like bite. Pick flowers in the morning when they are fully open, and pick leaves while they are young and tender. Deadhead spent flowers to keep the plant blooming, or leave some to set seed: the green seed pods can be pickled like capers. At the end of the season, pull the plants up and compost them. 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 |
|---|---|---|
| Big leaves, no flowers | soil too rich | Stop feeding and grow nasturtiums in poor soil. |
| Plants covered in aphids | aphids attracted to the plant | Leave them if the nasturtiums are a trap crop, or spray them off. |
| Seedlings cut at the base | cutworms | Use a collar around seedlings and check the soil at night. |
Big leaves, no flowers
Nasturtiums in rich soil grow enormous leaves and almost no flowers. They are one of the few plants that flower better when they are hungry, so never feed them and do not plant them in freshly manured soil.
Plants covered in aphids
A nasturtium black with aphids looks alarming, but if you planted it as a trap crop, it is doing its job — the aphids are on the nasturtium instead of your vegetables. Leave it, or spray the aphids off with water if the plant is suffering.
Seedlings cut at the base
A seedling cut clean through at soil level is cutworm damage. Push a cardboard collar around each seedling at planting time, and check the soil around damaged plants — the caterpillar is usually just under the surface.
Frequently asked questions
How long does it take to grow nasturtiums?
From planting to maturity takes 50–60 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 nasturtiums?
Space nasturtiums 8–12 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 nasturtiums need?
Nasturtiums 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.
Are nasturtiums edible?
Yes — the flowers and young leaves are edible, with a peppery taste like watercress, and the green seed pods can be pickled like capers. Only eat flowers you have grown yourself without sprays, and wash them first.
Do nasturtiums keep aphids off vegetables?
They work as a trap crop: aphids prefer nasturtiums to most vegetables, so planting nasturtiums nearby draws aphids away from your crops. Check the nasturtiums regularly and remove them if they become overwhelmed.