Growing nasturtiums in USDA Zone 3 means gardening with a short, cool season and winter lows in the range -40 to -30°F. The average last spring frost falls in the range May 15–Jun 1 and the average first autumn frost in the range Sep 1–15. Those are USDA/NOAA zone averages, not promises for any one garden — check your local extension service. This guide covers when to plant nasturtiums in Zone 3, and what soil, spacing, sun, water and care it needs.
Zone 3 at a glance
USDA Zone 3 has average winter lows of -40 to -30°F, and frost can linger into late spring and return early in autumn. Choose varieties suited to a short season, start indoors where the crop allows it, and protect plants at both ends of the season — a cold frame, cloche or low tunnel is often the difference between a harvest and an empty bed.
| Detail | Zone 3 guidance |
|---|---|
| Average last spring frost | May 15–Jun 1 (average/range) |
| Average first autumn frost | Sep 1–15 (average/range) |
| Days to germination | 7–14 days |
| Days to maturity | 50–60 days |
| Sowing | Direct sow (May 15 to Jun 1) |
| Transplanting | After the last frost (Jun 1–Jun 15) |
| Bloom / harvest | Jul 4–Jul 31 |
| Sun | full sun |
| Soil pH | 6.0–7.5 |
| Spacing | 8–12 inches |
| Water needs | moderate |
When to plant nasturtiums in Zone 3
Sow nasturtiums directly once frost is past (roughly May 15 to Jun 1). The average last spring frost falls in the range May 15–Jun 1, and the average first autumn frost in the range Sep 1–15, leaving a frost-free season of about three months in an average year. Those are USDA/NOAA zone averages, not promises for any one garden — check your local extension service. Allow 50–60 days to maturity, roughly Jul 4–Jul 31. The planting calendar hub gives the Zone 3 picture month by month, and the frost date calculator turns your frost averages into sowing dates.
Starting nasturtiums in Zone 3
For direct sowing, wait until the soil is warm and all frost is past (roughly May 15 to Jun 1), sow where the plants will grow, and thin to the spacing below. Seeds germinate in 7–14 days. Do not rush nasturtiums into cold soil — seed sown too early rots rather than germinating, and a second sowing in warm soil usually overtakes the first.
Nasturtiums are fast, cheerful annuals whose flowers and leaves are edible, and they do best in poor soil — rich soil gives leaves at the expense of flowers. They also work as a trap crop, drawing aphids away from other plants, so many gardeners plant them at the edge of the vegetable bed.
If a late frost is forecast after you have planted out, cover plants overnight with fleece, an upturned bucket or a cloche, and remove the cover in the morning so plants do not overheat.
Soil, spacing, sun and water
Nasturtiums grows best in full sun, in soil with a pH of 6.0–7.5. Test your soil through your local extension service rather than guessing, and dig in well-rotted compost before planting to improve drainage and moisture holding. Space plants 8–12 inches apart — in a short season it is tempting to crowd plants in, but crowded plants stay small and invite disease, so use a plant spacing calculator if you are laying out a bed. Nasturtiums needs moderate water: water when the top inch of soil feels dry, water at the base in the morning, and mulch to hold moisture.
Companion planting
Good companions for nasturtiums include lavender, marigolds, garlic, chives. The companion planting finder can suggest combinations for your whole bed. Avoid planting nasturtiums next to plants that compete for the same light, water and nutrients, and rotate crops each year where you can — growing the same crop in the same spot year after year builds up pests and diseases in the soil.
Pests and problems
The common pests and problems to watch for with nasturtiums are aphids, slugs, cutworms. Inspect plants regularly, especially the undersides of leaves, and act early: hand-pick larger pests, wash aphids off with a strong jet of water, and remove badly affected leaves rather than waiting for the problem to spread. A pest identifier helper can help narrow down what is eating your plants.
Cold is the biggest problem in Zone 3, ahead of any pest: a late spring frost or an early autumn frost can end the season overnight, so keep row cover ready and cover plants whenever frost is forecast. Good air circulation also matters — plants spaced properly and watered at the base stay drier and healthier than crowded plants watered from above.
Bloom, cutting and aftercare
For nasturtiums, the harvest is the flowering season itself — size, colour and firmness tell you more than any date. Pick or cut in the morning, handle gently, and use the flowers promptly. Deadhead spent flowers regularly to keep plants flowering, and use a harvest date calculator to estimate your flowering window from your sowing or transplant date. If frost is forecast before the season has finished, pick what you can rather than losing it to one cold night.
Related guides in this series: Nasturtiums in Zone 2 shows how the timing shifts in a colder zone, and Sweet Peas in Zone 3 is another crop for the same Zone 3 season. The Zone 3 May guide covers what else to plant and do that month.
Frequently asked questions
When should I plant nasturtiums in Zone 3?
Work back from the average last frost in the range May 15–Jun 1: start indoors where needed, sow hardy types a few weeks before that date, and do not put tender plants outside until frost is past. Check your local extension service — these are zone averages.
Can I grow nasturtiums outdoors in Zone 3?
Yes, with the right variety and timing — but be realistic: the frost-free window is about three months, so choose short-season varieties, start indoors where possible, and use a cloche or low tunnel for tender plants.
How long does nasturtiums take to grow in Zone 3?
Seeds germinate in 7–14 days, and the crop takes 50–60 days to maturity. In Zone 3, cool soil can slow growth, so allow the longer end of the range.
What soil and spacing does nasturtiums need in Zone 3?
Nasturtiums needs full sun and soil pH 6.0–7.5, spaced 8–12 inches apart. Dig in well-rotted compost, water deeply, mulch, and test your soil through your local extension service.