RHS Growing Guides
How to grow broccoli
Our detailed growing guide will help you with each step in successfully growing Broccoli.
Getting Started
Broccoli, or sprouting broccoli, is a delicious, nutritious and easy-to-grow member of the cabbage family. It forms multiple small clusters of purple or white buds for harvesting from mid-summer onwards. Winter varieties provide especially valuable harvests right through to spring.
Calabrese, on the other hand, produces a large central green head (that’s confusingly called broccoli in supermarkets and recipes).
Broccoli produces repeated harvests of tasty purple or white florets for up to two months – it is traditionally a winter/early spring crop, but newer varieties offer harvests from summer onwards, depending on the sowing time. The more compact, faster-growing summer varieties are best for smaller plots, while the more traditional winter- and spring-cropping varieties form large plants, up to 90cm (3ft) tall and wide, and can take eight months or more to mature. Still, they provide a valuable crop at an otherwise lean time of year and you don’t need many plants to enjoy ample pickings. Broccoli can also be expensive to buy, so is well worth growing.
Broccoli is a brassica, so should be grown with its other cabbage relatives in crop rotations, and it needs protection from the usual brassica pests and diseases – see Problem solving, below.
Month by Month
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Choosing
There are many broccoli varieties to choose from, for sowing and harvesting at different times. Traditional varieties are slow growing and hardy, sown in spring or early summer and forming large plants that crop in winter and the following spring. They take up a lot of space over a long period, but do provide valuable fresh harvests when little else is available.
If you don’t have the time or space for these, there are newer, smaller, faster-growing varieties for harvesting from mid-summer to late autumn. Check seed packets for sowing and harvesting times, as well as plant sizes and spacings.
You can choose from purple or white florets – purple varieties tend to be hardier and more productive, but both are attractive, delicious and well worth growing.
Broccoli is usually most successful in cooler summers, as hot weather can cause plants bolt (flower prematurely) – in warmer regions, grow bolt-resistant varieties.
For the most reliable broccoli 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 broccoli and many other crops.
You can see many crops, including broccoli and other brassicas, growing in the veg plots at the RHS gardens, so do visit to explore how they are grown, compare the varieties and pick up useful tips and inspiration.
Some broccoli seeds are sold specifically for growing as micro-greens indoors, giving you speedy harvests of nutritious, tasty seedlings to add to salads.
What and where to buy
Broccoli seeds are widely available from garden centres and online gardening retailers. Young plants may also be available in spring and early summer from the same sources, but the choice of varieties will be more limited.
Recommended Varieties
Very hardy,cropping over a long period. Produces large deep purple spears with good flavour.
A very errect plant which will crop from January to Mid-March. Easy to pick and has excellent colour.
An extremely vigorous and heavy cropping variety with large tender shoots. Plants go on to produce many side shoots giving a...
Preparing the Ground
Broccoli grows best in firm, fertile, well-drained soil, in sun or very light shade. It forms quite tall plants, so choose a sheltered spot where they won’t be buffeted by strong winds. Avoid soil that gets waterlogged, especially during winter if growing an overwintering variety.
If your soil is very acidic, apply lime the winter before sowing, to raise the pH and deter clubroot disease. Broccoli prefers a pH of 6 to 7.
Before sowing or planting, weed thoroughly and dig in two buckets of well-rotted manure or garden compost per square metre/yard. Ideally do this several months beforehand, to allow the ground to settle. If done just before planting, firm the soil well by treading it down using shuffling steps, then rake smooth.
Add 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.
Sowing
Broccoli seeds can be sown from March to June – indoors from March or outdoors from April. It’s best to sow broccoli in small batches several weeks apart, to provide regular pickings over a long season.
Broccoli should be grown with other cabbage relatives in crop rotations, to avoid any build-up of pests and diseases in the soil.
Sowing indoors
From March, you can start broccoli off in a greenhouse or on a sunny windowsill. You can continue sowing small batches through to June, or start sowing outdoors (see below) from April.
When sowing indoors, it’s best to use a modular tray to minimise root disturbance when transplanting later. Fill with seed compost, water well, then sow two seeds per module, 2cm (¾in) deep.
Sowing indoors is useful if you want an early harvest, giving plants a head start. It’s also beneficial if you have clubroot disease in your soil – ensure plants have a well-developed root system before being moved into the ground and they should be less severely affected.
Seeds should germinate within two weeks without any additional heat. After germination, thin out the seedlings, removing the smaller or weaker one to leave one per module. Water regularly and keep in good light. Apply a general-purpose liquid feed every week.
When the young plants are 10–15cm (4–6in) tall with a good rootball, move them outdoors – see Transplanting, below.
Another increasingly popular option, when sowing indoors, is to grow broccoli as micro-greens. Simply sow the seeds into a small seedtray at any time of year and harvest the tasty nutritious seedlings after just a few weeks, adding them to salads or using as a garnish.
Sowing outdoors
You can sow broccoli seeds outdoors from April to June – either on a temporary basis in a seedbed (for transplanting later – see below) or straight into their final position if you have space. Prepare the ground as explained above, then make a shallow drill about 2cm (¾in) deep and water along the base.
If sowing in a seedbed, sow as thinly as possible, ideally 7.5cm (3in) apart – or thin out to this distance once seedlings appear. If sowing in their final position, sow three seeds every 60–80cm (24–30in), depending on the variety, then thin out each cluster to one strong seedling as soon as they are large enough to handle.
After sowing:
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Cover the ground with fleece to exclude cabbage root fly
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Control slugs and snails, otherwise they will devour your seedlings as soon as they appear
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Weed and water regularly
Transplanting
Choose a site in sun or very light shade and prepare the ground as detailed above. Water the plants well, both before and after moving.
Plant the young broccolis deeper than they were previously growing, with the lowest leaves at the surface, so they root deeply and firmly.
Space broccoli 60–80cm (24–30in) apart, depending on the variety/ultimate size, with a similar distance between rows, then water in well. Check individual seed packets for exact spacings – generous distances between plants ensures good air circulation, which reduces disease, and encourages more side-shoots, which should give you larger harvests.
Plant Care
Broccoli needs protection from pests such as cabbage butterflies and pigeons, so cover with fine-mesh netting at all times. Weed between plants regularly, water during dry spells, feed to boost growth and support taller plants with a sturdy cane.
Watering
Water broccoli seedlings and young plants regularly until well established.
After that, only water during dry weather, every fortnight or so, to avoid any check in their growth, which can lead to bolting (premature flowering). Take care not to overwater winter varieties, to ensure they cope well with lower temperatures.
Mulching
Apply a thick layer of garden compost to the soil to help hold moisture around the roots. Mulch will also help to deter weed germination.
Feeding
When broccoli plants are about 20cm (8in) tall, apply a nitrogen-rich fertiliser, such as sulphate of ammonia, at a rate of 35g (1oz) per square metre/yard.
Supporting plants
Broccoli can reach about 90cm (3ft), so should be given support, especially in exposed locations. If these top-heavy plants are buffeting around by the wind, this can loosen the roots and hinder growth. So before any autumn gales arrive, pile soil up around the base of the stem to help stabilise the plants and/or insert a sturdy cane to hold them securely.
Protecting from pests
Broccoli is susceptible to all the usual brassica pests, so keep them protected at all times. Insect-proof mesh or fleece, supported on canes and pinned to the ground, should deter cabbage caterpillars, cabbage root fly and pigeons. See Problem solving, below, for more tips.
Harvesting
Broccoli is ready to harvest when the small heads, or spears, are well formed but still tightly in bud. Remove the whole shoot, cutting at the base, with about 10cm (4in) of stem and any small leaves, which can all be eaten.
Take the central spear first, then more will form on the sideshoots, which can be harvested over the following weeks. Check plants regularly, so you catch them before the clusters of buds start to open. The more shoots you harvest, the more the plants will produce.
Broccoli can be cooked in various ways – lightly steamed, sautéed or stir-fried – until tender, succulent and delicious. It can be eaten as a side dish or given pride of place in a wide range of delicious meals. Purple varieties generally turn green when cooked. Broccoli is best used as fresh as possible, but can be kept in the fridge for a few days and freezes well.
Problems
Broccoli usually grows and crops well, although it may bolt (flower prematurely) in hot weather.
As it’s a brassica, broccoli is susceptible to several pests and diseases that affect the cabbage family, including clubroot and cabbage root fly. It is best grown under fine-mesh netting to protect it from cabbage caterpillars and pigeons. Cabbage whitefly and aphids may sometimes be problematic.
If you have clubroot disease in your soil, start broccoli off indoors so it has a well-developed root system before being moved into the ground. Plants should then be less severely affected.
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