Broccoli: Sowing, planting and harvest calendar

Before sowing broccoli under cover, choose a variety suited to your climate and intended harvest season. Large-headed broccoli, often called calabrese, and sprouting broccoli do not always follow the same sowing schedule. March and April often suit the first sowings of large-headed types in temperate climates, but check the seed packet. Sow small batches at intervals if you want to spread out planting.

Use clean pots or a module tray with drainage holes. Fill them with fine, free-draining seed compost and moisten it before sowing. Place two seeds in each module, about 2 cm deep, following the variety’s instructions, then cover them and water gently. Keep the compost moist without leaving water standing in the tray underneath.

Put the containers somewhere bright and well ventilated. A reasonably mild sheltered space usually allows germination without extra heating; seedlings often appear within about two weeks, depending on conditions. Avoid overheating in direct sun and poor light that produces stretched stems. Ventilate any cover and remove it once seedlings emerge.

Once the first true leaves appear, keep one strong seedling per module by cutting the weaker one at its base. Preserve the root ball and avoid leaving plants until their roots become crowded. When they are well rooted and about 10 to 15 cm tall, gradually harden them off outdoors before planting at the spacing recommended for their variety.

You can sow broccoli outdoors in spring or early summer once the soil is workable and the weather supports steady germination. Adapt the timing to your variety and local climate: heading broccoli and sprouting types do not all follow the same cycle. Avoid sowing into waterlogged ground or just before a spell of intense heat.

Choose a bright position sheltered from wind, with fertile, well-drained soil. Remove weeds and break up the surface into fine crumbs. Make a drill about 2 cm deep, moisten it, distribute the seeds without crowding them and cover with fine soil. Water gently so the seeds stay in place, then keep the surface moist until seedlings emerge.

In a nursery bed, leave about 7 to 8 cm between young plants that you intend to transplant. When sowing in the final position, thin each cluster to one strong seedling. Allow the mature spacing recommended for your variety: large sprouting types take up much more room than compact heading broccoli. Protect the young leaves with suitable insect mesh and check for slugs too. Mulch does not replace these protections; wait until seedlings are clearly visible before bringing it close to them.

Plant your broccoli when the young plants have a good root system, several true leaves and a height of about 10 to 15 cm. The right planting period depends on the variety and intended harvest: do not assume every broccoli type should go outside at the same time. Avoid very hot days, frozen soil and waterlogged ground.

Choose a bright, sheltered position with fertile soil that holds moisture without staying saturated. Prepare it ahead of time, adding well-rotted compost if needed. Gradually harden off plants raised under cover. Water their root balls before removing the pots and handle them carefully to minimise root damage.

Dig a hole wide enough to take the intact root ball and set the plant a little deeper, up to the level of its lowest leaves without burying them. Fill the hole and firm the soil with your hands so it makes good contact around the roots. Water generously after planting.

Follow the spacing for your variety: compact heading broccoli and large sprouting types need different amounts of room. Add insect protection with enough space for growth underneath. Keep the root balls moist while the plants establish, then add mulch without piling it against the stems.

Harvest your broccoli while the flower buds are still tightly packed and closed. Cut a head promptly if it starts to loosen, especially in warm weather. Do not always wait for a large central head: its size depends on the variety and growing conditions. Heading types often crop in summer or autumn, while some sprouting varieties are ready in winter or the following spring.

Use a clean, sharp knife to cut the main head with a section of tender stem. With sprouting types, pick the ready shoots with their edible stems rather than pulling up the plant. Keep healthy leaves and smaller shoots that are still developing. Depending on the variety, further side shoots may extend your harvest over several weeks.

Check the plants regularly so you can pick those shoots before the flowers open. A small harvest at the right stage is better than a head that has become loose and fibrous. Chill the harvested parts promptly and use them within the next few days. For longer storage, blanch them before freezing. Discard any rotting parts and wash your harvest before preparing it.