Nasturtiums prefer direct sowing in the garden after all danger of frost has passed. Knowing exactly when to plant nasturtiums is the key to getting those vibrant blooms and peppery leaves all season long. Plant them too early, and frost will kill them. Plant them too late, and you miss weeks of color.
This guide covers everything you need. We will look at soil temperature, indoor starting, and regional timing. You will get clear steps so your nasturtiums thrive.
When To Plant Nasturtiums
The best time is spring, after the last frost date. Soil temperature should be at least 55°F (13°C). Nasturtiums are tender annuals. They cannot handle freezing temperatures.
Check your local frost dates. A quick online search with your zip code gives you the average last spring frost. Wait one week after that date to be safe.
Soil Temperature Matters Most
Nasturtium seeds germinate best in warm soil. Cold, wet soil causes seeds to rot. Use a soil thermometer to check. Insert it two inches deep. If it reads below 55°F, wait.
- Ideal soil temp: 60-70°F (15-21°C)
- Minimum soil temp: 55°F (13°C)
- Too cold: Seeds rot or germinate slowly
You can warm the soil by covering the bed with black plastic for a week. This speeds up planting by a few days.
Direct Sowing Is Best
Nasturtiums have fragile roots. They dislike transplanting. Direct sowing is the simplest method. It avoids root shock and gives stronger plants.
- Prepare the soil. Loosen it to 6 inches deep.
- Sow seeds 1 inch deep and 10 inches apart.
- Cover with soil and water gently.
- Keep soil moist until sprouts appear (7-14 days).
If you must start indoors, use peat pots. This lets you plant the whole pot without disturbing roots. Start seeds 2-3 weeks before your last frost date. Harden off seedlings gradually over a week.
Regional Planting Guides
Your location changes the calendar. Here is a breakdown by climate zone.
Cold Climates (Zones 3-5)
Last frost is usually late May to early June. Wait until the ground is workable and warm. Do not rush. A late spring snow can kill seedlings.
- Start indoors: 2-3 weeks before last frost (early May)
- Direct sow: Late May to early June
- Fall planting: Not recommended; frost comes too early
In short summers, choose dwarf varieties. They bloom faster. Trailing types may not flower before frost.
Temperate Climates (Zones 6-8)
Last frost falls between mid-April and mid-May. This is the sweet spot for nasturtiums. You have a long growing season.
- Direct sow: Mid-April to mid-May
- Succession planting: Sow every 3-4 weeks until late summer
- Fall planting: Sow in late August for autumn blooms
Succession planting gives continuous flowers. Sow a new batch every few weeks. This works well for cutting gardens.
Warm Climates (Zones 9-11)
Frost is rare or nonexistent. You can plant in fall, winter, or early spring. Avoid the hottest summer months. Nasturtiums stop blooming in extreme heat.
- Fall planting: September to November
- Winter planting: December to February (if mild)
- Spring planting: February to April
- Summer planting: Avoid; heat causes leggy growth
In very hot areas, plant in partial shade. Morning sun with afternoon shade works best. Water regularly to keep soil cool.
Planting Nasturtiums From Seed
Seeds are large and easy to handle. They look like small, wrinkled peas. No special treatment is needed, but a few tricks help.
Soaking Seeds
Some gardeners soak seeds overnight. This softens the hard seed coat. It can speed germination by a day or two. But it is not required.
If you soak, use warm water. Plant immediately after soaking. Do not let seeds sit in water for more than 12 hours. They can rot.
Planting Depth And Spacing
Nasturtium seeds need darkness to germinate. Bury them 1 inch deep. Space them according to variety.
- Dwarf varieties: 8-10 inches apart
- Trailing varieties: 12-18 inches apart
- Container planting: 3-4 seeds per 10-inch pot
Thin seedlings after they emerge. Keep the strongest one. Overcrowding reduces airflow and increases disease.
Watering After Planting
Keep soil consistently moist but not soggy. Use a gentle spray to avoid washing seeds away. Check daily. Seeds need moisture to swell and sprout.
Once seedlings appear, water less often. Deep watering once a week is enough. Nasturtiums prefer slightly dry conditions. Overwatering causes yellow leaves.
Transplanting Nasturtiums
Transplanting is possible but tricky. Only do it if you must. Use biodegradable pots to minimize root disturbance.
When To Transplant
Move seedlings outdoors after all frost danger passes. They should have 2-3 true leaves. Harden them off over 7-10 days.
- Place seedlings outside for 1 hour on day one.
- Increase time by 1 hour each day.
- Bring them indoors at night.
- After 7 days, leave them out overnight if temps stay above 50°F.
Transplant on a cloudy day or in late afternoon. This reduces transplant shock. Water well after planting.
Spacing For Transplants
Space plants the same as direct-sown seeds. Dig a hole slightly larger than the pot. Place the whole pot in the ground. Cover with soil and water.
Do not disturb the roots. Peat pots break down naturally. Remove any pot edges sticking above soil to prevent wicking moisture.
Growing Nasturtiums In Containers
Containers are great for small spaces. They also let you control soil and drainage. Choose pots with drainage holes.
Best Time For Container Planting
You can plant containers earlier than garden beds. Move them indoors during cold snaps. Start seeds 4-6 weeks before your last frost date.
- Indoor start: 4-6 weeks before last frost
- Move outdoors: After last frost, when nights are above 50°F
- Fall containers: Plant in late summer for autumn color
Container plants dry out faster. Water more often, especially in hot weather. Use a quality potting mix, not garden soil.
Varieties For Containers
Dwarf and trailing types work best. Dwarf varieties stay compact. Trailing types spill over edges.
- ‘Alaska’ series: Variegated leaves, compact
- ‘Jewel’ series: Dwarf, bright colors
- ‘Empress of India’: Trailing, deep red flowers
- ‘Whirlybird’ series: Upright, no trailing
Mix varieties for a colorful display. Pair with other annuals like petunias or marigolds.
Common Planting Mistakes
Even experienced gardeners make errors. Avoid these to keep nasturtiums healthy.
Planting Too Early
Cold soil kills seeds. Do not plant before your last frost date. Even a light frost damages tender growth. Wait until the soil is warm.
If you plant early and a cold snap hits, cover seedlings with row cover. Remove it when temps rise. This buys you a few degrees of protection.
Overwatering
Nasturtiums are drought-tolerant once established. Too much water causes root rot and yellow leaves. Let the top inch of soil dry between waterings.
In containers, ensure good drainage. Empty saucers after rain. Wet feet are a common killer.
Too Much Fertilizer
Rich soil produces lots of leaves but few flowers. Nasturtiums bloom best in poor soil. Avoid high-nitrogen fertilizers. Use a balanced, low-nitrogen feed if needed.
If your plants are lush but flowerless, stop fertilizing. Cut back on watering. They will often bloom in response to stress.
Harvesting And Using Nasturtiums
All parts are edible. Flowers, leaves, and seeds have a peppery taste. Harvest in the morning when they are crisp.
When To Harvest
Pick flowers when fully open. Leaves are best when young and tender. Older leaves become tough and spicy. Seeds can be pickled like capers.
- Flowers: Open, vibrant color
- Leaves: Small to medium size
- Seeds: Green, firm, before they dry
Harvest regularly to encourage more blooms. Deadheading spent flowers extends the season. Remove faded flowers weekly.
Storage Tips
Fresh nasturtiums last a few days in the fridge. Place them in a damp paper towel inside a bag. Use within 3 days for best flavor.
You can dry flowers for later use. Hang them upside down in a dark, airy space. Crushed dried flowers add color to salts and teas.
Frequently Asked Questions
Can I plant nasturtiums in summer?
Yes, but avoid the hottest months. In warm climates, plant in fall or spring. In cooler zones, summer planting works fine. Provide afternoon shade.
How late can I plant nasturtiums?
Plant up to 8 weeks before your first fall frost. They need 60-70 days to bloom. Check your first frost date and count backward.
Do nasturtiums come back every year?
No, they are annuals. They complete their life cycle in one season. However, they self-seed readily. You may see new plants next year from dropped seeds.
Should I soak nasturtium seeds before planting?
Soaking is optional. It can speed germination by a day or two. But direct sowing without soaking works just as well. Soak only if soil is warm.
Can I start nasturtiums indoors?
Yes, but use peat pots to avoid root disturbance. Start 2-3 weeks before last frost. Harden off seedlings carefully. Direct sowing is easier and more reliable.
Final Tips For Success
Nasturtiums are forgiving plants. They thrive on neglect. Poor soil, little water, and full sun produce the best blooms. Do not baby them.
Plant them near vegetables to repel pests. Aphids love nasturtiums, making them a trap crop. Check leaves regularly and hose off aphids if needed.
Remember the golden rule: wait until frost danger passes. Warm soil and patience give you a stunning display. Enjoy the bright flowers and spicy leaves all summer long.
Now you know exactly when to plant nasturtiums. Get your seeds ready, check your frost dates, and sow with confidence. Your garden will thank you.