Growing Cauliflower and Broccoli Successfully

When and how to sow cauliflower and broccoli?

Each variety of cauliflower and broccoli has its ideal sowing period: this information is indicated on the seed packet, and it’s important to refer to it.

The sowing period for cauliflower runs from January to August, for example:

• ‘Merveille de toutes saisons’ is sown from January to June for a harvest from June to November,
• ‘Alpha 6 Fortados’ is sown from February to May for a harvest in July–August,
• ‘Clovis F1’ is sown from April to August for a harvest from September to January.

Broccoli sowing takes place from March to late July, depending on the variety, for a harvest spanning June to December:

• ‘Verdia F1’ is sown from March to July for a harvest from July to October,
• ‘Summer Purple’ is sown from March to June for a harvest from July to November,
• ‘Romoso Calabrese’ is sown from May to August for a harvest from October to December.

Direct sowing in the ground is possible, but preparing or purchasing seedlings for transplanting is the most common method. Once well-developed, the seedlings are planted in their final position in the vegetable garden.

Sowing under cover

This is done indoors or in a heated shelter from late autumn to late spring, or in a cold frame or nursery for the rest of the year.

• Fill pots or seed trays with special seed compost.
• Sow the broccoli and cauliflower seeds. They should be buried to a depth of about 1 cm.
• Cover them lightly with compost
• Water gently with a fine spray
• Remember to keep the substrate moist (but not waterlogged) until germination.
• When the young seedlings are strong enough to handle, transplant them into pots and, for seedlings grown under heated cover, gradually acclimatise them to cooler temperatures before transplanting them into the garden, once the risk of frost has passed.

Direct sowing

• Start by preparing the soil: weed, loosen the soil, and add well-rotted compost or manure
• Draw furrows about one centimetre deep, spaced 60 to 80 cm apart for cauliflower and 50 to 60 cm for broccoli
• Sow the seeds and cover them with a thin layer of fine soil
• All that remains is to water.
• Once the seedlings are well-developed, thin them out, keeping only one plant every 60 to 80 cm for cauliflower and 60 cm for broccoli

Where to plant cauliflower and broccoli?

Cauliflower and broccoli are quite demanding vegetables, requiring well-manured soil, rich in nitrogen and potash. It’s best to add a generous amount of compost or well-rotted manure (about 3/4 kg per m2) in autumn, working it into the top 5 cm of soil after thoroughly loosening the ground. They thrive in deep, slightly acidic soils and need plenty of sunlight, though they can tolerate light shade. Cool, rainy climates suit them perfectly.

These cabbages grow well alongside many other vegetables, such as lettuce or tomatoes. However, avoid planting them near other brassicas, courgettes, fennel, lamb’s lettuce, leeks or strawberries.

When and how to plant them?

It is possible to sow directly in open ground, but preparing or purchasing seedlings for transplanting is the most common method. Once well developed, the plants are placed in their final position in the vegetable garden. They should be planted in a sunny, sheltered spot in well-prepared, warmed soil: weeded, loosened with a spade or garden fork, then raked with a rake to create fine soil.

Planting distances depend on the growth of each variety. Generally, allow 60 to 80 cm between rows and 60 to 80 cm between plants for cauliflower; and 50 to 60 cm between rows and 60 cm between plants for broccoli.

• Soak the root ball in water for a few moments before planting
• Dig a hole about twice the size of the root ball
• Place the plant and cover with fine soil. The plants should be buried up to the first true leaves: new roots will form along the buried stem, ensuring better anchorage in the soil
• Broccoli plants grow tall—in windy locations, it is advisable to stake them
• Water generously
• To reduce watering needs, we recommend mulching the soil with thin, successive layers of grass clippings, ideally mixed with dead leaves
• During cultivation, water moderately but regularly

How to care for them?

Maintaining these cabbages involves regular weeding, hoeing and watering. Their growth is slow, so these tasks recur frequently over a long period. They can be spaced out or significantly reduced if you mulch the soil with thin successive layers of pre-dried grass clippings, for example.

What are the pests and diseases?

Cabbages are quite susceptible to diseases and pests. When growing them, you may encounter:

• the cabbage root fly whose larvae devour the roots,
• the cabbage white butterfly, whose caterpillars ravage the foliage,
• the cabbage gall midge which attacks the central bud (“blind cabbage”),
• flea beetles which meticulously perforate the leaves of brassicas in general.

Various control methods exist against these pests (cardboard collars against the fly, spraying with Bacillus thuringiensis, manual collection of caterpillars…) but to keep them at bay, the best prevention is to securely place an insect-proof mesh.

Regarding diseases, clubroot is the most virulent. It manifests as wilting foliage accompanied by swellings on the stem base and roots. There is no natural solution, but the best prevention is to respect crop rotation in the vegetable garden by not growing cabbage in the same spot for at least 5 years.

When and how to harvest them?

Harvesting cauliflower should be done when the heads are well-formed but before they start to split. Broccoli is harvested in two stages: first the central head, located at the top of the plant, followed by the side shoots that develop afterwards. Use a knife for harvesting.

To go further

Discover everything you need to know about cabbage in our comprehensive guide!