Calabrese, commonly known as calabrese broccoli, is a hardy vegetable grown for its large green heads and tender flowering shoots. It forms a central dome-shaped head made up of tightly packed flower buds, supported by thick, edible stems and surrounded by broad blue-green leaves. Once the main head is harvested, many varieties continue to produce smaller side shoots, extending the harvest period.

Originating from Italy, calabrese thrives in cool to mild conditions and is typically grown for autumn harvests, though some varieties are suited to spring cropping. It is valued for its mild, slightly sweet flavour and high nutritional content, being rich in vitamins, fibre, and antioxidants. Calabrese is versatile in the kitchen and can be steamed, stir-fried, roasted, or added to soups and pasta dishes, making it a staple crop in vegetable gardens.

How To Grow

1. Choose the Right Time Calabrese prefers cool to mild weather. Sow seeds in spring for summer harvests or early summer for autumn harvests. Avoid extreme heat, which can cause bolting.

2. Choose the Right Location Plant in full sun. Use fertile, well-drained soil. Shelter plants from strong winds.

3. Sowing Seeds Sow seeds in pots or seed trays about 1 cm (½ inch) deep. Keep soil moist; seedlings appear in 7–10 days. Transplant when seedlings are 10–15 cm (4–6 inches) tall.

4. Transplanting Space plants 45–60 cm (18–24 inches) apart. Plant firmly and water well.

5. Watering Water regularly to keep soil evenly moist. Lack of water can result in small or poor-quality heads.

6. Feeding Feed with compost or a nitrogen-rich fertilizer once established. A second feed after harvesting the main head encourages side shoots.

7. Care and Protection Keep beds weed-free. Mulch to retain moisture. Protect from pests such as cabbage white butterflies, aphids, and pigeons using netting.

With steady care, calabrese grows quickly and rewards gardeners with generous harvests of nutritious, flavourful heads and shoots.

Harvesting

1. When to Harvest Harvest when the main head is firm, tight, and deep green. The flower buds should be compact and unopened. This is usually 8–12 weeks after planting, depending on variety.

2. How to Harvest Use a sharp knife. Cut the main head with 10–15 cm (4–6 inches) of stem attached. Cut at a slight angle to prevent water collecting on the stem.

3. Encourage Side Shoots After harvesting the main head, leave the plant in the ground. Continue watering and feeding lightly. Smaller side shoots will form and can be harvested over several weeks.

4. Harvest Regularly Check plants every few days once heads begin forming. Harvest promptly to prevent buds from opening into yellow flowers.

5. After Harvest Care Use broccoli fresh for best flavour. Can be refrigerated for short-term storage or blanched and frozen.

Harvesting at the right time ensures tender stems, good flavour, and extended cropping from each plant

Common Problems

Common Problems with Calabrese

Pests

Cabbage White Butterfly & Caterpillars One of the most damaging pests. Adults lay eggs on leaves; caterpillars hatch and rapidly devour foliage. Check the undersides of leaves regularly and remove egg clusters and caterpillars by hand. Use fine mesh netting as a physical barrier throughout the growing season.

Cabbage Aphids Grey-green aphids cluster on new growth and under leaves, weakening plants and potentially spreading disease. Squash small colonies by hand or spray with an insecticidal soap solution. Encourage natural predators such as ladybirds and lacewings.

Root Fly (Cabbage Root Fly) Larvae tunnel into roots, causing wilting and collapse of young plants. Use brassica collars around the base of transplants and cover with fine mesh netting to prevent egg-laying.

Whitefly Tiny white insects on leaf undersides, causing yellowing and sticky residue. Control with yellow sticky traps and insecticidal soap sprays.

Slugs and Snails Attack young seedlings and transplants, especially in damp conditions. Use slug traps, copper tape, or apply organic pellets around plants.

Diseases

Clubroot A soilborne fungal disease causing swollen, distorted roots and wilting. There is no effective chemical cure. Improve drainage, raise soil pH with lime, and practise a strict crop rotation of at least four years. Use resistant varieties where available.

Downy Mildew Yellowish patches on upper leaf surfaces with grey mould underneath, favoured by cool, damp conditions. Improve air circulation by correct spacing, remove affected leaves promptly, and avoid wetting foliage when watering.

Black Rot Bacterial disease causing yellow V-shaped lesions on leaf margins and blackened veins. Remove and destroy affected plants. Avoid overhead watering and practise good crop rotation.

Powdery Mildew White powdery coating on leaves in warm, dry spells. Improve air circulation and keep plants well watered at the roots.

Other Issues

Bolting (Premature Flowering) Heads can open rapidly into yellow flowers in hot or dry conditions. Harvest promptly as soon as heads are firm and fully formed. Maintain consistent watering and avoid transplanting stress.

Poor Head Development Caused by irregular watering, nitrogen deficiency, or overcrowding. Ensure adequate feeding, correct spacing, and steady moisture throughout growth.

Tipburn Brown, scorched leaf edges caused by calcium deficiency or irregular watering. Maintain consistent soil moisture to aid nutrient uptake.