Nasturtium seeds germinate quickly in warm soil, but planting them too early in cold ground leads to poor sprouting. Knowing exactly When To Plant Nasturtium ensures you get those vibrant blooms and edible leaves all season long. This guide walks you through the perfect timing based on your climate, growing method, and goals.
When To Plant Nasturtium
The best time to plant nasturtium seeds is after the last spring frost has passed and the soil has warmed to at least 60°F (15°C). In most regions, this falls between early spring and late spring, depending on your local weather patterns. Planting too early in cold, wet soil often results in rot or stunted growth, while waiting too long can shorten your blooming window.
Nasturtiums are sensitive to frost. Even a light freeze can kill young seedlings. So, always check your local frost dates before putting seeds in the ground.
Understanding Your Growing Zone
Your USDA hardiness zone determines your planting calendar. Here is a simple breakdown:
- Zones 3-5 (Cold climates): Plant seeds indoors 4-6 weeks before the last frost, or direct sow in late May or early June.
- Zones 6-7 (Moderate climates): Direct sow in mid to late April, or early May once soil warms.
- Zones 8-10 (Warm climates): Plant in early spring (February to March) or even in fall for winter blooms.
Always watch the weather forecast. A sudden cold snap can damage young plants. If you are unsure, wait an extra week. Nasturtiums grow fast once conditions are right.
Indoor Seed Starting For Nasturtium
Starting seeds indoors gives you a head start, especially in short growing seasons. It also protects seeds from birds and pests. Follow these steps for best results:
- Fill small pots or seed trays with seed-starting mix.
- Plant seeds about 1/2 inch deep. Nasturtium seeds are large, so space them 2-3 inches apart.
- Water gently and place in a warm spot (70°F or 21°C).
- Keep soil moist but not soggy. Seeds sprout in 7-14 days.
- Once seedlings have two sets of true leaves, harden them off by moving them outside for a few hours each day.
- Transplant outdoors after all frost danger has passed.
Indoor starting works well for climbing varieties. It gives them time to develop strong roots before moving outside. Remember to use biodegradable pots if possible, because nasturtium roots are delicate and dislike disturbance.
When To Start Indoors
Start seeds indoors about 4 to 6 weeks before your last expected frost date. For example, if your last frost is May 15, start seeds around April 1 to April 15. This timing allows seedlings to be ready for transplanting right after frost passes.
Do not start too early. Nasturtium seedlings can become leggy if kept indoors too long. They need bright light and consistent warmth. If you lack a sunny window, use grow lights.
Direct Sowing Nasturtium Outdoors
Direct sowing is the simplest method. Nasturtiums dislike root disturbance, so planting seeds directly in the garden often yields stronger plants. Wait until the soil is warm and workable.
Here is how to direct sow:
- Prepare the soil by loosening it to about 6 inches deep. Nasturtiums prefer poor to average soil. Rich soil leads to more leaves and fewer flowers.
- Soak seeds overnight in warm water to speed up germination. This softens the hard seed coat.
- Plant seeds 1/2 to 1 inch deep, spacing them 8-12 inches apart for bush types, or 12-18 inches for climbers.
- Water well after planting, then keep the soil evenly moist until seedlings emerge.
- Thin seedlings to the strongest ones once they are 2-3 inches tall.
Direct sowing works best when soil temperatures are consistently above 60°F. Use a soil thermometer to check. If the ground is still cold, wait. Patience pays off.
Best Months For Direct Sowing
In most regions, direct sowing happens from April to June. Here is a general guide:
- Northern climates: Late May to early June.
- Central climates: Mid-April to mid-May.
- Southern climates: February to March, or September to October for fall planting.
You can also plant in succession every 3-4 weeks for continuous blooms. This works well in mild climates where summers are not too hot.
Planting Nasturtium In Containers
Containers offer flexibility. You can move pots to catch sun or avoid frost. Plant nasturtium seeds in pots 4-6 weeks before the last frost if starting indoors, or directly in outdoor containers after frost passes.
Use containers with drainage holes. Fill with a light potting mix. Do not use garden soil, it compacts in pots. Plant seeds 1/2 inch deep, 2-3 seeds per pot for bush types. Thin to the strongest seedling.
Container-grown nasturtiums need more frequent watering than garden plants. Check soil daily. They also benefit from occasional feeding with a diluted, low-nitrogen fertilizer.
When To Plant In Containers
You can plant container nasturtiums earlier than garden beds if you protect them from frost. Move pots indoors or into a garage during cold nights. This gives you a 2-4 week head start. For outdoor containers, wait until nighttime temperatures stay above 50°F (10°C).
In warm climates, you can plant container nasturtiums year-round. Just avoid the hottest months if temperatures exceed 90°F (32°C).
Seasonal Planting Guide
Nasturtiums thrive in cool to warm weather. They struggle in extreme heat or cold. Here is a seasonal breakdown:
Spring Planting
Spring is the primary planting season. Direct sow or transplant after the last frost. Spring-planted nasturtiums bloom from early summer until the first fall frost. They enjoy the mild temperatures and longer days.
If you plant in early spring, use row covers or cloches to protect from late frosts. This is especially important in zones with unpredictable weather.
Summer Planting
In hot climates, summer planting is risky. Nasturtiums stop blooming in intense heat. If you live in zones 8-10, plant in late summer for fall blooms. In cooler regions, you can plant in early summer for a late-season display.
Water deeply during dry spells. Mulch around plants to keep roots cool. Choose heat-tolerant varieties like ‘Empress of India’ or ‘Alaska’ for better performance.
Fall Planting
Fall planting works in mild winter areas (zones 9-11). Plant seeds in September or October for winter flowers. Nasturtiums grow slowly in cooler weather but produce vibrant blooms. They often survive light frosts if protected.
In colder zones, fall planting is not recommended. Seeds will not survive freezing ground. Instead, collect seeds for next spring.
Factors That Affect Planting Time
Several factors influence when you should plant nasturtium. Consider these before deciding:
- Soil temperature: Seeds need at least 60°F to germinate. Use a thermometer.
- Frost dates: Know your last spring frost and first fall frost dates.
- Rainfall: Avoid planting during heavy rain periods. Wet soil causes rot.
- Sunlight: Nasturtiums need full sun (6+ hours daily) for best blooms. Partial shade reduces flowers.
- Variety: Climbing types take longer to bloom than bush types. Adjust planting time accordingly.
If you live in a microclimate, such as a valley or coastal area, adjust your schedule by 1-2 weeks. Observe local gardens for cues.
Common Planting Mistakes
Avoid these errors to ensure success:
- Planting too early: Cold soil kills seeds or causes slow growth.
- Overwatering: Nasturtiums prefer moderate moisture. Soggy soil leads to root rot.
- Rich soil: Too much nitrogen produces lush leaves but few flowers.
- Ignoring spacing: Crowded plants compete for nutrients and air.
- Skipping hardening off: Indoor seedlings need gradual exposure to outdoor conditions.
Another common mistake is planting in deep shade. Nasturtiums need at least 4-6 hours of sun daily. Without enough light, they become leggy and bloom poorly.
How To Extend The Blooming Season
With proper timing, you can enjoy nasturtium flowers from late spring until frost. Here are tips:
- Plant in succession every 3-4 weeks until midsummer.
- Deadhead spent flowers regularly to encourage new blooms.
- Water consistently during dry periods. Stress reduces flowering.
- Cut back leggy growth in midsummer to promote bushier plants.
- In warm climates, provide afternoon shade to prevent heat stress.
You can also collect seeds from spent flowers. Nasturtium seeds are easy to save and replant next season. Let them dry on the plant before harvesting.
Regional Planting Calendar
Here is a quick reference for major US regions:
| Region | Direct Sow Window | Indoor Start |
|---|---|---|
| Northeast | Late May to early June | Mid-April |
| Southeast | March to April | February |
| Midwest | Mid-May to early June | Early April |
| Southwest | February to March | January |
| Pacific Northwest | April to May | March |
| California Coast | March to April or September | February |
Adjust these dates based on your specific microclimate. Check local gardening forums for more precise advice.
Frequently Asked Questions
Can I Plant Nasturtium Seeds In July?
Yes, in cooler climates. July planting gives you fall blooms. In hot regions, wait until late August or September.
How Late Can I Plant Nasturtium?
You can plant up to 8-10 weeks before the first fall frost. This allows time for flowering. In mild climates, plant until early fall.
Do Nasturtiums Need Full Sun?
Yes, for best blooms. They tolerate partial shade but produce fewer flowers. Full sun (6+ hours) is ideal.
Should I Soak Nasturtium Seeds Before Planting?
Soaking overnight in warm water softens the seed coat and speeds germination. It is optional but helpful, especially in dry soil.
Can I Plant Nasturtium In Pots?
Absolutely. Containers work well. Use well-draining potting mix and water regularly. Plant after frost danger passes.
Final Tips For Success
Nasturtiums are forgiving plants. Even if you plant a bit late, they often catch up quickly. Focus on soil temperature and frost dates. Use a soil thermometer for accuracy.
If you miss the spring window, try a fall planting in mild areas. Or start seeds indoors for a late start. Nasturtiums grow fast, so you can still enjoy flowers within 6-8 weeks.
Remember to water moderately and avoid overfertilizing. Poor soil actually encourages more blooms. With the right timing, your garden will be filled with cheerful flowers and tasty leaves all season.
Now you know exactly When To Plant Nasturtium for your climate. Get your seeds ready, check the weather, and enjoy the process. Happy gardening!