Romanesco

Sun

Full sun; light afternoon shade can help in warmer districts.

Water

Keep soil evenly moist, supplying about 1-1.5 in (25-38 mm) of water weekly during dry weather. Avoid alternating drought and heavy watering.

Soil

Fertile, moisture-retentive but well-drained soil, ideally pH 6.5-7.5. Avoid compacted or waterlogged ground.

Height

1.5-3 ft (0.45-0.9 m)

Spread

1.5-2.5 ft (0.45-0.75 m)

Flowers

Yellow flowers if plants bolt or remain in the ground beyond the edible-head stage.

Foliage

Large, waxy blue-green leaves surround and partly shelter the central green head.

Growth

Fast in cool conditions; harvest timing varies considerably with variety and planting season.

Care needed

Medium

• Low allergen
• Edible

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

Difficulty

Moderate

Toughness

Needs looking after

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

1. Planting day

   0.5 ft (0.15 m)

2. After 1 year

   2.2 ft (0.68 m)

   full size

Full size in one season.

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

Fast

• Mix mature compost into the bed before planting and space plants about 2 ft (0.6 m) apart.
• Water at soil level before the root zone dries out, especially while heads develop.
• Apply a balanced vegetable fertiliser at planting, following the label; feed again during leafy growth if needed.
• Mulch around established plants to conserve moisture, keeping mulch clear of the stems.
• Cover young plants with insect mesh, leaving room for growth and securing the edges.

Pruning. No routine pruning is needed. Remove badly damaged or diseased leaves, but retain healthy foliage to support head growth.

Cut the main head when its spiral cones are firm and tightly packed, before they loosen or flower buds begin to open. Use a sharp knife to cut the stem below the head, retaining a few protective leaves; unlike sprouting broccoli, Romanesco usually gives one main harvest.

Late winter

In cool regions, sow indoors for a spring crop only if the variety suits spring planting.

Spring

Harden off young plants and transplant into prepared soil; protect them from severe frost and cover against insects.

Summer

Sow autumn-cropping varieties according to local guidance; keep seedlings cool, moist and growing steadily.

Late summer

Transplant autumn crops in cool and temperate regions, allowing enough time for heads to mature before severe cold.

Autumn

Check developing heads frequently and harvest while the cones remain tight.

Winter

In mild, frost-light regions, maintain winter crops; elsewhere remove spent plants and plan a rotation away from brassicas.

• Plant in orderly rows in a kitchen garden, where the blue-green leaves give structure before heads form.
• Use as a seasonal centrepiece in a raised edible bed, with low lettuces around the edges.
• Repeat small groups through a potager for a rhythm of broad foliage and sculptural green heads.
• Grow in a large container with fertile compost and reliable watering for a temporary courtyard food crop.

Garden styles it suits: Potager (kitchen garden), Edible landscape, Homestead, Farmhouse, Architectural minimal and Green on green.

Plant it with: Lettuce, Spinach, Spring onions, Beetroot, Calendula and Sweet alyssum.

Wildlife: Leaves feed cabbage butterfly and moth caterpillars. Plants allowed to flower provide nectar and pollen for bees and other insects, although the edible head is then lost.

• Cabbage caterpillars: inspect leaf undersides and remove eggs and larvae; use well-sealed insect mesh before butterflies and moths lay eggs.
• Flea beetles: small holes can severely check young plants; protect seedlings with fine insect mesh and maintain steady watering.
• Clubroot: swollen roots and wilting indicate this persistent soil disease; remove affected plants, avoid moving contaminated soil and use a different growing area.
• Small, loose or missing heads: heat, drought, root disturbance or checked seedling growth can spoil the crop; choose a locally suitable variety and planting season, and maintain even moisture.

The head and leaves are edible and are not generally considered toxic to people, cats or dogs in ordinary food amounts, though large portions may cause digestive upset. Romanesco is not generally regarded as a poisonous garden plant for horses, but large quantities of brassica foliage can cause digestive and other health problems; do not offer it as bulk feed.

• Cauliflower (Brassica oleracea Botrytis Group)

  Most cauliflower has a rounded, densely curded head rather than Romanesco's pointed cones arranged in obvious spirals; some cauliflower varieties are also green.

• Broccoli (Brassica oleracea Italica Group)

  Broccoli usually has rounded clusters of visible green flower buds on branching stalks rather than a compact head of lime-green spiral cones.

Romanesco means 'Roman' or 'of Rome' in Italian, referring to its association with the Rome region.

Propagation. Grow from seed, usually in modules before transplanting while young. Use the seed supplier's local sowing window, as varieties differ in their seasonal requirements; saved seed may cross with other flowering Brassica oleracea crops and may not come true.

Accepted botanical name

Brassica oleracea

In the US and Canada

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

Native range

France, Great Britain and Spain.

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.