How to grow calabrese

A popular and tasty crop, calabrese produces large domed green heads up to 15cm (6in) across, for harvesting in summer and autumn. Growing calabrese yourself means you can enjoy it freshly picked, when its mild flavour and many beneficial

To grow well, plants need a wide range of nutrients in various amounts, depending on the individual plant and its stage of growth. The three key plant nutrients usually derived from soil are nitrogen, phosphorus and potassium, while carbon, oxygen and hydrogen are absorbed from the air. Other vital soil nutrients include magnesium, calcium and sulphur. Gardeners can add nutrients by applying fertilisers (either artificial or naturally derived) to boost plant growth and improve flowering and fruiting.

• Calabrese plants produce a large central green head of tightly packed buds, ready to harvest from mid-summer to mid-autumn (this is confusingly called broccoli in supermarkets and recipes) 

• Broccoli plants (also known as sprouting broccoli) produce much smaller clusters of purple or white

  A bud is a small, undeveloped shoot that contains the potential for new growth. Buds are typically found on stems, where they can be apical (found at the tip) or axillary (found between leaf axils) and may develop into leaves, shoots or flowers.

  buds on the tips of leafy stems. For more on this crop, see our guide to growing broccoli 

Calabrese is mainly sown in spring, either indoors or outside, and is ready to harvest in three or four months, from July to October, depending on the variety and sowing time. It grows up to 60cm (2ft) tall and wide, forming a large central green head, which is a cluster of tightly packed flower buds. After cutting the main head, further smaller heads form on side-shoots, extending the harvest for up to eight weeks.

Calabrese is a member of the cabbage (brassica) family, so should be grown alongside its relatives in crop rotations and protected from the main brassica pests and diseases – see Problem solving, below.

The main head is ready to harvest when large and firm but still tightly in bud. Delicious and versatile, calabrese is best lightly steamed or stir-fried and can be used in all kinds of dishes. It’s particularly popular in Italian cuisine and is named after Calabria in southern Italy. Often hailed as a superfood, calabrese is rich in nutrients, including anti-cancer compounds.

You’ll find a wide selection of calabrese varieties available as seed, offering variations in sowing/harvesting times, plant size, and resistance to bolting, clubroot and other diseases. Most form a large domed green head, followed by smaller heads for harvesting over a long period. Choose compact varieties if space is tight, as they can be grown closer together.

For the most reliable calabrese varieties, look for those with an RHS Award of Garden Merit (AGM), which shows they performed exceptionally well in trials – see our list of AGM fruit and veg for recommended varieties of calabrese and many other crops.

To help you choose calabrese varieties, why not visit the veg plots in the RHS gardens? You’ll see many crops, including calabrese and other brassicas, and can explore how they’re grown, compare the varieties and pick up useful tips and inspiration.

Calabrese prefers firm, fertile, well-drained soil in a sheltered sunny or lightly shaded spot. If possible, choose and prepare your growing site in advance: 

• The previous autumn, dig in two bucketfuls of well-rotted manure or garden compost per square metre/yard, to allow the ground time to settle over winter. If done closer to planting time, firm the soil really well by treading it down, shuffling back and forth over it, then rake it smooth.

• If your soil is very acidic, apply lime the previous winter to raise the pH and deter clubroot disease. Calabrese prefers soil with a pH of at least 6.8.

• Rake in a high potassium general fertiliser, such as Vitax Q4 – use one and a half handfuls per square metre/yard, or three handfuls if no manure or garden compost has been added.

Calabrese seeds are generally sown between February and June – indoors from late winter into mid-spring, then outdoors from mid-spring to early summer.

If you sow several small batches a few weeks apart, you can spread out your harvests and avoid gluts.

Calabrese should be grown in the same bed as its other cabbage relatives in crop rotations, to avoid any build-up of pests and diseases in the soil.

Calabrese is a fast-growing brassica and needs little maintenance apart from weeding regularly and watering during dry spells. Keep plants fully covered with fine-mesh netting to protect them from cabbage butterflies and pigeons.

Calabrese usually grows and crops well, but it may bolt (flower prematurely) during hot weather. Choose a bolt-resistant variety in warmer regions.

It is susceptible to several pests and diseases that affect the cabbage family, including clubroot and cabbage root fly. Covering the crop with fine-mesh netting, supported on a framework, will keep several pests at bay, including cabbage caterpillars and pigeons. Cabbage whitefly and aphids can also cause problems. Wide spacing between plants helps to deter pests and fungal diseases. 
 
If you have clubroot disease in your soil, sow calabrese indoors so it can develop a good root system before being moved into the ground. It should then be less severely affected.