How to sow and grow broccoli

Broccoli has a bit of an image problem. For a lot of us it’s the thing that got pushed to the side of the plate as kids, boiled into sad, grey-green submission and served with a generous helping of resentment. But homegrown broccoli? That’s a different beast entirely. Sweet, nutty, properly crunchy and picked minutes before it hits the pan, it’s the sort of thing that converts even the most committed broccoli-dodger. And the best news of all: growing broccoli is far easier than its supermarket reputation suggests.

In this guide we’ll walk you through everything you need to sow, grow and harvest broccoli in the UK, from picking your variety to outwitting the cabbage root fly. Roll up your sleeves, this one’s a keeper.

Choosing your broccoli varieties

Broccoli is a wonderfully broad church. The word actually covers several different cropping styles, so it’s worth knowing what you’re after before you reach for the broccoli seeds.

• Calabrese is the big-headed, supermarket-style broccoli most people picture. Our Early Green Calabrese is a classic Italian heirloom that matures faster than most, producing a generous central head and then keeping on giving with sprouting side shoots once the main one’s been cut.
• Purple sprouting broccoli is the hardy hero of the hungry gap, cropping its tender purple spears through late winter and early spring when little else is going. Rudolph is one of the earliest to crop, grown under cover, you could be harvesting in time for Christmas dinner.
• White sprouting broccoli offers the same generous, cut-and-come-again habit with striking pale florets. White Eye is, in our humble opinion, the best-tasting early variety around.
• Leaf broccoli is the rare, rule-breaking cousin grown for its leaves rather than its flower buds. Our ribbony-leaved Leaf Broccoli Ribbons and the magnificently named Leaf Broccoli Bastard are both delicious steamed and drizzled with good olive oil.

If you can’t choose (we don’t blame you), grow a few of each for a supply that stretches right across the seasons. Browse the full range of broccoli seeds here.

When to sow broccoli

Like the rest of the brassica family, broccoli much prefers cool, steady conditions to baking heat. Most varieties can be sown from early spring through to early summer, with sprouting types sown a little later for a winter and spring crop.

The exact timing depends on your variety, always check the back of your seed packet but as a rule of thumb:

• Calabrese: sow from March through summer for a continual supply.
• Purple and white sprouting broccoli: sow March to June for spears the following late winter and spring.

Sowing little and often (every few weeks) keeps you in broccoli for longer, rather than landing you with a glut all at once and a freezer full of florets.

How to sow broccoli seeds

You can either start your broccoli off under cover or sow broccoli seeds outdoors directly where they’re to grow. We tend to favour module trays, it gives the young plants a protected, pest-free start and makes transplanting a doddle.

Sowing in modules (our preferred method): Fill module trays with a good-quality, peat-free seed compost and firm it gently. Sow your seeds around 1cm deep, one or two per cell, and water them in. Broccoli doesn’t need extra heat to germinate, but a warm, bright spot like a sunny windowsill will speed things along, expect to see broccoli seedlings within a week or so. Sowing very early in the season? Our guide to using heat and grow lights will help you give them the best start. And keep an eye out for damping off, that heartbreaking fungal seedling-killer, by not overwatering and keeping the air moving.

Sowing direct: If you’d rather sow broccoli seeds outdoors, wait until the soil has warmed a little in spring. Sow thinly into a shallow drill about 1cm deep in well-drained soil, then thin the seedlings as they grow so the strongest young plants have room to develop. Slugs and snails adore tender young brassica seedlings, so keep a watchful eye out (more on the pest brigade below).

Preparing the soil and planting out

Broccoli is a hungry crop, and it’ll reward you for a bit of effort up front. Choose a sunny or lightly shaded, sheltered spot with fertile, well-drained soil. Dig in plenty of well-rotted manure or garden compost a few weeks before planting to give your plants the rich, firm ground they love. (‘No dig’ gardeners, simply spread your compost on the surface and let the worms do the heavy lifting.)

Brassicas like firm soil, so don’t be shy about treading it down gently before you plant. Once your young plants have four or five true leaves and are large enough to handle, usually around five weeks from sowing, it’s time to harden them off and plant them out. Set them a little deeper than they sat in their pots to give a good, sturdy stem, and space them generously: around 45cm apart for calabrese, and at least 60cm for the bigger sprouting types. Firm them in well and water thoroughly.

Caring for your broccoli plants

Watering: Keep your plants well watered, especially during dry spells and hot weather. Broccoli that’s left to dry out can bolt (rush to flower) or sulk into producing small, disappointing heads. A mulch around the base will help retain moisture and keep weeds down.

Feeding: A regular feed with a balanced organic fertiliser keeps broccoli growing strong and productive right through the season.

Support: The taller sprouting varieties can get top-heavy and catch the wind, so pop in a sturdy cane to keep them upright if you’re on an exposed plot.

The pest brigade: Brassicas attract more than their fair share of admirers, and not the welcome kind.

• Cabbage root fly lays its eggs at the base of young plants and the larvae then tunnel into the roots. A collar around the stem or a covering of fine mesh foils them nicely.
• Club root is a soil-borne disease that distorts the roots improving drainage, raising the soil pH and rotating where you grow your brassicas all help keep it at bay.
• Slugs and snails will make short work of young plants, so stay vigilant.
• Cabbage white butterflies and their ravenous caterpillars can strip a plant to a skeleton in days.

The simplest defence against most of these is a good physical barrier. We never grow brassicas without netting, a covering of fine insect netting over your young plants keeps the whole rogues’ gallery out while still letting in light, air and rain. For more on outwitting the caterpillar crew, read our guide to protecting your brassicas from cabbage white butterflies. You’ll find everything you need in our crop protection and support range.

How to harvest broccoli

Here’s the moment you’ve been waiting for. Harvest broccoli while the heads are still tight and the flower buds are firmly closed, once they start to yellow and open they’ve gone past their best (though the bees certainly won’t complain).

For calabrese, cut the main central head first with a sharp knife. Don’t pull up the plant, leave it in the ground and it’ll produce a flush of smaller side shoots over the following weeks, giving you a second, third and fourth helping for your trouble.

For sprouting broccoli, snap or cut the spears when they’re around 10cm long, before the flowers open. The golden rule here is to pick regularly: the more you harvest, the more shoots the plant produces, so really don’t be shy. And resist the urge to strip off the big lower leaves, they’re busy protecting the next batch of developing shoots.

From a humble tray of seed compost to a plate of sweet, just-picked spears, growing your own broccoli is endlessly satisfying and a world away from those sad supermarket florets. Whether you’re after a big summer head of calabrese or tender purple spears to brighten the depths of winter, there’s a broccoli for every plot and every season.