Nasturtium

How to recognise it

Habit

Trailing or climbing plant with fleshy stems 1–3 m long; bushy varieties stay compact, 25–40 cm.

Leaf

Round and shield-shaped, 5–15 cm, with the stalk in the centre and veins radiating like spokes; bluish-green and water-repellent.

Flower

Funnel-shaped, 4–6 cm, with five petals and a long nectar-filled spur at the back. Orange, yellow, red or cream, sometimes blotched.

Fruit/Seed

A fruit that splits into three ribbed, pea-sized parts, green at first and later beige.

Stem and roots

Fleshy, brittle stems; the leaf stalks twist around supports to climb. Shallow, fibrous roots.

Look-alikes

Dwarf nasturtium (Tropaeolum minus) is smaller in all its parts. The climbing canary creeper (Tropaeolum peregrinum) has deeply lobed leaves and small, fringed yellow flowers.

Flowering: June–October · Pruning: November

Why grow it?

• Flowers for months, from June until the first night frost, with little care.
• Long-tongued bumblebees take nectar from the spur at the back of the flower.
• A food plant for the caterpillars of the large white butterfly, which also live on cabbages.
• Edible: the peppery leaves and flowers brighten up a salad, and the green seeds can be pickled like capers.
• Quickly covers bare soil, climbs a fence or trails over the edge of a container or wall.
• Easy and quick: the large seeds are ideal for sowing with children.

Nasturtium: where does it grow best?

• In the wild: moist mountain slopes and valleys in the Andes, in a climate without hard frost.
• Sun or light shade; it flowers best in sun.
• Poor to ordinary, well-drained soil: on rich, fertilised soil it makes lots of leaves and few flowers.
• Ideal along the edge of the vegetable garden, against a fence, in containers, hanging baskets and on banks.
• Allow 25–40 cm between plants; trailing varieties cover up to 1 m² per plant.

Goes well with

• Sunflower: Tall stems it can climb; together a cheerful summer picture.
• Pot marigold: Orange and yellow in the same vegetable garden, and edible too.
• Courgette: Together with the large courgette leaves it covers the soil in the vegetable garden.
• Chives: Purple pompoms and fine leaves as an edging in the vegetable garden.
• Cosmos: Airy, tall flowers behind the low, trailing nasturtium.

Nasturtium: when and how to plant it?

1. Buy seed or young plants from a garden centre or nursery; never dig plants up from the wild.
2. Sow from mid-May, after the last night frost, directly outside, 2 cm deep, 2–3 seeds per spot. No cold period is needed.
3. Want earlier flowers? Sow indoors in April in individual pots: it dislikes being pricked out.
4. Keep the spots 25–40 cm apart and thin to the strongest plant.
5. Water after sowing and keep the soil moist until the seedlings appear, after 1–2 weeks.
6. Put climbing varieties next to a fence, mesh or canes that the leaf stalks can twist around.

Care

Water

Water in dry spells, especially in containers and pots. In open ground it copes fairly well with drought.

Feeding

Not needed. It flowers best on poor soil; fertiliser mainly produces leaves.

Training

Guide climbing stems towards a fence or let them trail freely over the ground. Cut back stems that grow too long.

Harvesting

Pick leaves and flowers regularly for the kitchen: this encourages new flowers.

Letting seed drop

Let a few seeds fall: after a mild winter they germinate by themselves the following spring.

Tip: Sow it in the poorest spot in the garden and never feed it: the leaner the soil, the more flowers and the fewer leaves. Soaking the seed overnight makes it germinate faster.

Pruning and mowing

Pruning months: November.

When: No pruning is needed. Clear away the frosted plants in November.

How:

• In summer, cut back stems that are too long or have finished flowering: the plant soon regrows.
• Remove yellow leaves at the base to keep the plant fresh.
• After the first night frost the plant collapses, black and limp: pull out the remains or leave them as a mulch.
• Compost the remains; they rot down quickly.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

The usual way: sow outside from mid-May or indoors in pots in April. Collect the ripe, beige seeds in late summer and store them dry.

Cuttings

Double varieties set little seed: in August, take 8–10 cm cuttings, root them in a glass of water or in cutting compost and overwinter them frost-free in a light place.

Self-seeding

After mild winters, fallen seeds often germinate by themselves; move the seedlings in May.

Nasturtium: how does it get through the winter?

Hardy to 0 °C: protect in harsh winters.

• Not hardy: the first night frost kills the plant.
• Seeds in the soil often survive the winter and germinate by themselves in May.
• Cuttings of double varieties can be overwintered frost-free in a cool, light place indoors.
• Leave the dead stems on the ground as a cover; they rot down during the winter.

Diseases and pests

• Cabbage white caterpillars: Yellowish-green caterpillars with black spots strip the leaves. Pick them off, or let them have a few plants: it is their food plant.
• Black bean aphid: Black aphids on the stems and under the leaves. Spray them off with water; ladybirds and hoverflies clear them up.
• Slugs: They eat the seedlings. Sow indoors first or pick them off in the evening.
• Lots of leaves, few flowers: Soil too rich or too much shade. Do not feed, and sow in a sunny, poor spot.
• Late frost: A night frost in May kills young plants. Sow or plant out only after mid-May.

Through the year

• April: Sow indoors in individual pots.
• May: After mid-May, sow outside or plant out.
• June: Flowering begins. Guide climbing stems.
• July: Full flower. Pick leaves and flowers for the kitchen.
• August: Pickle green seeds. Take cuttings of double varieties.
• September: Collect ripe seeds and store them dry.
• October: Flowering until the first night frost.
• November: Clear away frosted plants or leave them as a mulch.

Did you know?

• Linnaeus saw shields in the round leaves and blood-stained helmets in the flowers, like a trophy on a battlefield: so he named the plant Tropaeolum, from the Greek tropaion, trophy.
• His daughter Elisabeth Christina Linnaea described in 1762 how the flowers seemed to give off flashes of light at dusk. Today we know it is an optical effect in our own eyes.
• Water drops roll off the leaf like beads: the surface is so water-repellent that the leaf stays dry.