Nasturtium

Sun

Full sun to partial shade; give afternoon shade in hot climates, though flowering declines in deep shade.

Water

Water moderately, allowing the soil surface to dry between waterings. Containers need more frequent checks; avoid persistently wet soil.

Soil

Well-drained, average to relatively poor soil. Rich soil and high-nitrogen feeding encourage leaves at the expense of flowers.

Height

Bushy forms: 1-1.5 ft (0.3-0.45 m); trailing forms can scramble 6-10 ft (1.8-3 m) high with support.

Spread

Bushy forms: 1-2 ft (0.3-0.6 m); trailing forms: 3-10 ft (0.9-3 m).

Flowers

Summer to the first frost in cool climates; often autumn to spring in mild, hot-summer climates. Flowers are yellow, orange, red, cream or combinations of these colours.

Foliage

Rounded, shield-shaped green leaves with radiating veins and the stalk attached beneath the leaf blade; some cultivated forms have cream-variegated leaves.

Growth

Fast; flowers often begin about 8-12 weeks after sowing.

Care needed

Low

• Sow directly into well-drained soil after frost risk has passed; young plants dislike root disturbance.
• Water seedlings regularly, then water established plants when the soil surface dries.
• Avoid routine feeding in garden soil; feed container plants lightly only if growth is weak.
• Give trailing forms netting or twiggy supports early, and guide shoots towards them.
• Remove unwanted seedlings and collect seeds before they drop where spreading is a concern.

Pruning. Pinch young shoot tips to encourage bushier growth, and shorten straggly stems during the growing season. Remove faded flowers to prolong flowering and pull out frost-killed plants.

Early spring

In cool climates, sow indoors in individual pots about 3-4 weeks before the last expected frost.

Late spring

Harden off indoor-grown plants and plant out, or sow directly, once frost risk has passed.

Early summer

Guide trailing shoots onto supports and pinch tips if you want denser growth.

Summer

Check containers for dryness, remove faded flowers and inspect shoot tips for aphids.

Autumn

Save ripe seeds from healthy plants; in mild, frost-free, hot-summer regions, sow for cool-season growth.

Late autumn

Clear frost-killed stems and remove unwanted seedlings before they become established.

• Edge vegetable beds with compact forms for edible flowers and a soft contrast to upright crops.
• Let trailing forms spill from hanging baskets, raised beds or large containers.
• Grow over a low fence or twiggy framework for quick, informal seasonal cover.
• Weave orange and red flowers among calendulas and salvias in a warm-coloured cottage border.

Garden styles it suits: Cottage garden, Potager (kitchen garden), Edible landscape, Pollinator garden, Small-space and Hot border.

Plant it with: Calendula, French marigold, Salvia, Swiss chard, Lettuce and Tomato.

Wildlife: Flowers provide nectar and pollen for visiting insects. Leaves support cabbage white caterpillars, and aphid colonies attract predatory insects; growing nasturtiums near brassicas does not reliably protect those crops.

• Aphids cluster on soft shoots: wash them off with water, pinch out heavily infested tips and leave room for ladybirds and other predators.
• Caterpillars chew leaves, especially cabbage white caterpillars: inspect leaf undersides and hand-pick where damage is unacceptable.
• Lots of leaves but few flowers: stop nitrogen-rich feeding and move future plantings into a sunnier, less fertile position.
• Yellowing and collapse in wet soil: reduce watering and improve drainage; discard plants with rotting roots.

Not known to be toxic to cats, dogs or horses. Flowers, leaves and green seeds are edible for people, but their pungent compounds can cause stomach irritation if eaten in large quantities. Use only plants correctly identified and grown without unsuitable pesticide treatments.

Where it spreads. Can self-seed aggressively in mild coastal climates. It is naturalised and treated as an environmental weed in parts of coastal Australia, including Western Australia, South Australia, Victoria and New South Wales, and can spread into coastal vegetation in California and New Zealand. Avoid planting beside natural areas where it already escapes.

• Canary creeper (Tropaeolum peregrinum)

  A climbing relative with deeply lobed leaves and small yellow flowers with fringed upper petals; garden nasturtium has mostly unlobed, rounded leaves and broader flower petals.

• Watercress (Nasturtium officinale)

  Despite its botanical name, watercress is unrelated. It grows in wet ground or water, has divided leaves and tiny white flowers, unlike the rounded leaves and large, colourful flowers of garden nasturtium.

Nasturtium comes from Latin words meaning 'nose-twister', referring to its peppery taste, while Tropaeolum refers to a trophy, recalling the shield-like leaves and helmet-like flowers.

Propagation. Sow seeds about 0.5-1 in (1.3-2.5 cm) deep after frost risk has passed, or start in individual pots indoors. Collect mature, plump seeds as they loosen from the plant and dry them before storage; seedlings from named varieties may differ from their parents.

Accepted botanical name

Tropaeolum majus

In the US and Canada

Introduced in Hawaii, the lower 48 states, Pacific Basin and Puerto Rico.

Native range

Peru.

Measured

Average height 30 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.