Nasturtium: Care and Growing Guide

What nasturtium is and why gardeners grow it

Nasturtium (Tropaeolum majus) is one of the easiest-to-grow annual flowers in the US, going from seed to bloom in 50–60 days. It thrives in poor soil, requires almost no maintenance, produces edible flowers and leaves, and actively deters aphids from vegetable crops.

Few plants offer this combination. Most edible flowers need rich soil and regular feeding. Nasturtiums do the opposite — they bloom most heavily when deprived of nitrogen and planted in lean, gritty soil. Add a bag of compost and you’ll get magnificent foliage, almost no flowers, and a disappointed gardener.

This quirk is also what makes nasturtiums so useful in vegetable gardens. They don’t compete with your tomatoes, cucumbers, or squash for nutrients. They fill space between plants, cover bare soil, and draw aphids away from your crops — all while providing edible harvests and color from June through frost.

In Nashville, Zone 6b, nasturtiums are one of the first seeds I direct-sow each spring. They reliably outlast most summer annuals and keep producing into October if aphid pressure and heat don’t overwhelm them.

Nasturtium varieties: bush vs. trailing

The two main nasturtium growth habits serve different garden functions. Choosing the wrong type for your space is the most common planting mistake.

Bush types produce more flowers per square foot and stay tidy in containers or at the front of vegetable beds. ‘Alaska’ has variegated white-streaked leaves that look attractive even when not in bloom.

Trailing types produce fewer flowers relative to vine length but are the most useful as trap crops — more surface area means more plant tissue to attract aphids away from your vegetables.

For edible flower production specifically, compact types give you more blooms per plant. ‘Jewel Mix’ produces a full range of colors — gold, orange, scarlet, cream — over an extended season.

How to grow nasturtiums from seed

Nasturtiums grow best from direct-sown seed. They develop a taproot system that resents being disturbed, and transplants started in pots often stall for 2–3 weeks after planting while they recover.

When to sow

Sow seeds outdoors after your last frost date when soil temperature reaches at least 50°F. Nasturtiums germinate best at 55–65°F. In USDA Zone 6 (Nashville, Tennessee area), this means direct-sowing in late April to early May. In Zone 8 (most of Texas and Georgia), sow in late March. In Zone 5 (upper Midwest), wait until mid-May.

A second sowing in mid-August in Zones 6–7 will produce a fall flush of flowers before frost. This fall-sowing strategy extends the season significantly and often produces the cleanest plants of the year, with fewer pest problems.

How to plant

1. Soak seeds in water for 12 hours before planting — this speeds germination by 3–4 days
2. Plant seeds 1 inch deep, 10–12 inches apart
3. Water well at planting; after that, water only when the top inch of soil is dry
4. Thin to 18–24 inches apart once seedlings reach 3 inches tall (for trailing types)
5. Expect germination in 7–14 days at correct soil temperatures

Soil and sun requirements

Nasturtiums need:

• Full sun to light part shade — minimum 6 hours direct sun for best flowering
• Poor to average, well-drained soil — no added fertilizer; avoid compost-enriched beds
• Moderate moisture — drought-tolerant once established; overwatering causes root rot

The “poor soil” rule is real and worth taking seriously. In trials I ran in my Zone 6b beds, plants grown in straight garden soil without amendments produced 3× more flowers per plant than those grown in my standard compost-amended vegetable bed mix.

If you’re growing in containers, use a basic potting mix with no added fertilizer. A mix designed for succulents or cacti works well.

Using nasturtiums as companion plants

Nasturtiums are among the most versatile companion plants in the vegetable garden. Their primary function is as a trap crop for aphids.

Nasturtium as an aphid trap crop

Aphids prefer nasturtiums over almost any vegetable. When you plant nasturtiums near susceptible crops, aphids colonize the nasturtiums first and in greatest numbers. The vegetables nearby stay relatively clean.

This works best with:

• Cucumbers — plant trailing nasturtiums at the base of cucumber trellises
• Beans — nasturtiums near pole beans reduce black bean aphid pressure; see bean companion plants for the full companion strategy
• Squash and zucchini — nasturtiums planted 18 inches from squash hills intercept aphids before they reach the squash

The key rule: Don’t remove aphid-covered nasturtiums. The infested plant is doing its job. Pull it only when it has served its purpose — typically late summer — or when the aphid colony is so heavy the nasturtium dies.

Other companion benefits

Beyond aphid trapping, nasturtiums offer:

• Pest deterrence for marigolds: pairing nasturtiums with marigolds creates a multi-layer pest deterrent border that discourages aphids, whiteflies, and some soil pests
• Pollinator attraction: nasturtiums bloom heavily and attract bumblebees, honeybees, and hummingbirds; see attract pollinators to your garden for a full companion planting strategy around pollinator needs
• Ground cover: sprawling nasturtiums suppress weeds and keep soil cool and moist between vegetable plants
• Nitrogen-free ground cover: because nasturtiums don’t need fertilizer, they’re one of the few ground covers that won’t compete with or over-enrich neighboring vegetables

For companion planting strategies specific to peppers, which have different pest pressure than beans or cucumbers, see companion plants for peppers.

Eating nasturtiums: flowers, leaves, and seeds

Nasturtiums are one of the most underused edible plants in US home gardens. Almost every part is edible, with a peppery, slightly mustard-like flavor.

Flowers: Best eaten fresh, the same day they’re picked. Add to salads, float on soups, or freeze in ice cubes for drinks. The flavor is mildly peppery with floral notes. All color varieties taste similar.

Leaves: Younger, smaller leaves are milder. Mature leaves get more peppery. Use them like watercress in salads, sandwiches, or as a wrap for soft cheese. Vitamin C content is higher than in most salad greens.

Seeds (unripe): Green, unripe nasturtium seeds can be pickled in brine to make a caper substitute with a sharp, tangy flavor. Harvest them when still bright green and firm. This is a relatively obscure culinary use but worth trying if you have a heavy seed set.

Harvest flowers early in the morning after dew dries. Pick consistently to encourage continued production — nasturtiums flower more heavily when you remove blooms before they set seed.

Do not spray nasturtiums you plan to eat with chemical pesticides. If aphids are overwhelming the plants you’ve set aside for eating, hose them off with water or relocate those specific plants away from the trap crop area.

Nasturtium care through the season

Nasturtiums are nearly maintenance-free once established, but a few care practices maximize season length.

Watering

Water deeply once or twice a week in dry periods. Nasturtiums tolerate short drought spells but drop flowers during extended drought. Do not overwater — soggy soil causes stem rot at the crown within 2–3 days.

Deadheading

Remove spent flowers before seed pods form to extend blooming. This is optional if you want seeds for pickling or for saving to replant next year. Letting plants set seed causes blooming to slow significantly in mid-summer.

Dealing with aphids on eating plants

If aphids colonize nasturtiums you’re growing for eating rather than as a trap crop, knock them off with a firm stream of water. This is sufficient — nasturtiums recover quickly. Aphids return within a week if populations are high, so repeat as needed or harvest more often to stay ahead of infested foliage.

End of season

Nasturtiums die at the first hard frost. In Zones 9–11, they may regrow from the crown or self-seed. In colder zones, pull plants after frost and compost them. Collect seeds from dried pods in early fall if you want to replant next year — they store well in a cool, dry location for up to 3 years.

Growing nasturtiums in containers

Nasturtiums are among the most reliable annual flowers for containers and window boxes. Bush varieties suit smaller pots; trailing types spill attractively from elevated planters.

Container tips:

• Use a 10–12 inch pot minimum for bush types; trailing varieties need a 14+ inch pot
• Plant 2–3 seeds per pot; thin to 2 plants after germination
• Use basic potting mix — no fertilizer added
• Water when the top 2 inches of soil are dry; containers dry out faster than ground beds
• Elevate containers or position trailing types at the edge of decks or raised beds to let vines cascade

Nasturtiums in containers are also effective at deterring aphids from nearby potted vegetables. Position a nasturtium pot near tomatoes or peppers to serve the same trap-crop function as in-ground planting.

For a comprehensive guide to container gardening with edible and ornamental plants, see container gardening small spaces.

Nasturtium compared to other easy-to-grow annuals

If you’re deciding between nasturtium and other fast-growing annuals, this comparison covers the key differences:

Nasturtium wins on: edibility, poor-soil tolerance, and pest management value. It’s the strongest choice if you want one annual that does multiple jobs in the vegetable garden.