Sea kale

Sun

Full sun; tolerates light shade but flowers and crops best in an open position.

Water

Water regularly during establishment and dry spring weather. Established plants tolerate drought, but dislike persistently wet roots.

Soil

Deep, freely draining sandy, gravelly or loamy soil; neutral to alkaline is ideal. Avoid waterlogged clay.

Height

2-3 ft (0.6-0.9 m)

Spread

2-3 ft (0.6-0.9 m)

Flowers

Late spring to early summer; branched clusters of small, fragrant white flowers.

Foliage

Large, rounded, fleshy blue-grey leaves with strongly waved edges; dies back for winter.

Growth

Moderate; allow two to three years to establish a strong crown.

Care needed

Low

• Pollinators
• Drought tolerant
• Cold hardy
• Low allergen
• Fragrant
• Edible

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

2. After 1 year

   1.5 ft (0.45 m)

3. After 2 years

   2 ft (0.6 m)

4. After 3 years

   2.5 ft (0.75 m)

   full size

About 3 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Native to

the UK

Growth rate

Moderate

• Choose a permanent position; mature plants have deep roots and resent moving.
• Water new plants through their first growing season, then during prolonged dry spells.
• Apply a light dressing of compost around the plant in spring, keeping it clear of the crown.
• Avoid heavy feeding, which encourages soft growth.
• Keep the crown free of wet leaves and soggy mulch over winter.
• Leave young plants unharvested for their first two growing seasons.

Pruning. Remove dead leaves in late autumn or winter without cutting into the crown. Cut spent flower stems to the base unless you want seed.

From the third spring, cover a dormant crown with an opaque forcing pot or bucket before shoots emerge to produce pale, tender stems. Cut shoots when about 6-9 in (15-23 cm) long, before the leaves unfold, taking only a few from each crown. Remove the cover after a short harvest period and let the plant grow freely for the rest of the season.

Late winter

Clear dead foliage and cover established crowns if you want blanched shoots.

Early spring

Plant nursery-grown plants in a permanent, freely draining position.

Spring

Harvest a few tender shoots from mature plants, then uncover them and allow full leaf growth.

Late spring

Enjoy the flowers and check young leaves for caterpillars and flea beetle damage.

Summer

Water during prolonged drought and remove spent flower stems unless saving seed.

Late autumn

Remove collapsed foliage and check that winter rain drains away from the crown.

• Use as a bold blue-grey foliage plant among low-growing plants in a sunny gravel garden.
• Combine with sea thrift and sea holly in coastal borders for contrasting leaf shapes and flower forms.
• Give it a permanent place at the edge of a vegetable garden, where harvesting will not disturb neighbouring crops.
• Repeat small groups through a white-flowered border for broad foliage beneath airy flower clusters.

Garden styles it suits: Coastal, Dry gravel garden, Potager (kitchen garden), Edible landscape, White garden and Low-maintenance.

Plant it with: Sea thrift, Sea holly, Lavender, Thyme, Santolina and Yarrow.

Wildlife: The fragrant flowers attract bees, hoverflies and other pollinating insects. Leaves can feed caterpillars of cabbage butterflies.

• Crown or root rot in wet soil: improve drainage before planting, use a raised bed if needed, and keep wet mulch away from the crown.
• Slugs and snails on emerging shoots: check at dusk, hand-pick, and remove nearby hiding places.
• Cabbage caterpillars stripping leaves: inspect leaf undersides and remove eggs and caterpillars; use insect mesh on plants grown mainly for food.
• Flea beetles making small holes in young leaves: protect young plants with fine insect mesh and keep them growing steadily with adequate water.

Not known to be toxic to people, cats, dogs or horses. Young shoots, leaves and flower buds are edible, although specific safety data for pets and horses are limited; do not use it as routine animal feed.

• Greater sea kale (Crambe cordifolia)

  Much taller in flower, often reaching 6-8 ft (1.8-2.4 m), with large, rough, green, heart-shaped leaves rather than fleshy blue-grey leaves.

• Sea beet (Beta vulgaris subsp. maritima)

  Has glossy green leaves and inconspicuous greenish flowers along upright stems, rather than waxy blue-grey leaves and branched clusters of white flowers.

Crambe comes from an ancient Greek name for cabbage, while maritima means 'of the sea', referring to its coastal habitat.

Propagation. Sow fresh seed in deep pots, removing the corky outer fruit casing carefully if practical; germination can be slow and uneven, and winter chilling may help. Root cuttings taken during dormancy are another reliable method. Use cultivated stock rather than collecting from wild coastal populations.

Accepted botanical name

Crambe maritima

In the US and Canada

Introduced in the lower 48 states.

Native range

Baltic States, Belgium, Bulgaria, Denmark, Finland, France, Germany, Great Britain, Ireland, Krym, Netherlands and North Caucasus.

Measured

Soil pH 7 to 7.5. Average height 50 cm.

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