How to grow cauliflowers

This tasty, nutritious crop likes deep, fertile soil and regular watering, especially in summer. In the shops, cauliflowers are almost always creamy white, but grow your own and you can enjoy orange, green or purple heads, as well as handy mini-caulis.

Moving a plant from one growing position to another, often from a pot to its final spot in the garden.

transplanted

When a vegetable plant starts flowering and forming seeds, often prematurely, making the crop unusable – salad leaves may turn bitter and root crops fail to swell. Adverse weather or changes in day length can cause bolting in a wide range of vegetables, including lettuces, onions , carrots and otheer root crops.

bolt

There are lots of cauliflower varieties to choose from, grouped according to harvesting time. There are faster-growing varieties for summer and autumn crops, and slower-growing varieties for harvesting in late winter and spring. If you buy several different types, you can have cauliflowers practically all year round.

Different varieties grow to various sizes, to suit whatever space you have available, from huge heads (curds) up to 30cm (1ft) across to mini-caulis just 10cm (4in) wide. Winter varieties tend to be larger and slow growing, taking up a lot of room for six months or more, so if you’re short on space, choose smaller, faster-growing summer or mini varieties. 

There are several different types, sown and harvested at different times: 

• Summer varieties – usually sow indoors from winter to early spring. They are fast growing and form smaller heads, ready to harvest in four or five months. They are generally easier to grow successfully than later varieties, especially if harvested before any hot, dry weather.

• Mini-cauliflowers are mainly summer varieties, grown at closer spacing to keep them small, and harvested at tennis-ball size. They are ideal if space is limited and can even be grown in containers. They are quick to mature, in as little as three months, and less prone to problems. 

• Autumn varieties – sow indoors or outdoors in mid- to late spring. They are slightly slower growing than summer types and bred to withstand higher summer temperatures, although light shade in the middle of the day is beneficial. They grow best in cool autumn weather and should be harvested before the first frosts.

• Winter varieties – sow indoors or outdoors from late spring to early summer. These are slow growing, taking six months or more to mature, forming large heads. They need wide spacing and can take up quite a lot of room over a long period. Most modern varieties are very hardy and can be harvested through to spring.

As well as traditional white or cream cauliflowers, there are varieties with striking purple, orange-yellow or lime-green heads for added ornamental appeal, both in the garden and on the plate. They generally keep their colour when cooked, unless boiled for too long. 

For consistent crops of tasty, high-quality caulis, it’s best to choose F1 hybrid varieties, and if you’ve ever had problems with clubroot disease, select resistant varieties. Look too for varieties with an RHS Award of Garden Merit (AGM), which shows they performed well in trials – see our list of AGM fruit and veg for RHS-recommended varieties of cauliflowers and many other crops.  

You can see many crops, including cauliflowers 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.

Choose a sunny site with deep, fertile soil that is moist but free-draining. Dig in a couple of bucketfuls of well-rotted manure or garden compost per square metre/yard, ideally the autumn beforehand so the ground has time to settle.  

Make sure you haven’t grown cauliflowers or other brassicas in that spot for at least two years – see our guide to crop rotation.

If your soil is acidic, apply lime the previous winter to raise the pH and deter clubroot disease. Cauliflowers prefer a pH of 6.5 to 7.5.

Immediately before sowing or transplanting, remove any weeds, then firm the soil by treading it thoroughly. Like most brassicas, cauliflowers need well-firmed ground.  

Then rake in a high potassium general fertiliser, such as Vitax Q4, at a rate of three handfuls per square metre/yard. 

Cauliflower seeds are usually sown indoors, but can also be sown outdoors from mid- to late spring. The main sowing season is March to May, although you can sow in January or February indoors – or even the previous autumn – for earlier harvests.

When sown outdoors, cauliflowers are traditionally started off in a separate ‘seedbed’, then transplanted to their final growing position, at a wider spacing, once they’re about 10cm (4in) tall. This helps to make best use of limited space during the prime spring growing season.

As cauliflowers tend to mature in a rush, avoid raising too many plants at a time, as they don’t store well. Sowing several small batches about three weeks apart will spread out your harvests.

Young cauliflower plants growing in a seedbed, raised from seed indoors or bought as plug plants should be transplanted to their final growing site when 10–15cm (4–6in) tall, at about six weeks old. Don’t delay too long, as disturbing the roots at a later stage can cause plants to bolt (flower prematurely), ruining the harvest.

Indoor-raised plants must be hardened off so they are acclimatised to outdoor conditions before transplanting.

Prepare the soil as explained above.
 
If their growth is checked at any time, cauliflowers are likely to produce small, deformed heads. To avoid this when transplanting, give them plenty of water before and afterwards.  

To transplant cauliflowers: 

• Make a hole with a trowel, deep enough so the plant’s lowest leaves will be at ground level  

• Gently place the plant in the hole, trying not to disturb the roots, then fill the hole repeatedly with water. Called ‘puddling it’, this also refills the hole with soil and ensures the plant is sitting in a large area of moist ground  

• Firm the soil really well around the plant

• 45–60cm (18–24in) apart for summer and autumn varieties 

• 70cm (28in) apart for larger winter varieties 

• 15cm (6in) apart for mini-caulis 

It’s important to give cauliflowers plenty of space, especially larger winter varieties. Wide spacing helps them grow bigger and keeps them healthier by allowing good air circulation and preventing any shading. Mini-cauliflowers are the exception and are planted closer to stunt their growth.  

Mini-caulis can also be planted in large, deep containers – up to four in a 40cm (16in) diameter container filled with multi-purpose compost.

Young cauliflower plants are vulnerable to various pests, especially slugs and snails, so put protection in place. Add a brassica collar to deter cabbage root fly and cover the crop with insect-proof mesh to keep cabbage white butterflies and pigeons away.

Cauliflowers require consistent moisture to form well-shaped heads and need protection from brassica pests at all times. In summer, hot sun can cause white cauliflower heads to turn yellow – to protect them, fold the leaves over the curd. In winter, protect the developing head from hard frosts in a similar way.

You can harvest cauliflowers throughout the year, depending on when you sow. They generally take three to six months from sowing to maturity, but growth rates vary according to the variety, size and weather conditions. 

Harvest cauliflowers as soon as the head is large enough, when still firm and compact. Don’t wait too long though – once it starts to separate, it’s past its best and will taste bitter. White varieties should be harvested before they turn yellow. Mini varieties can be harvested at tennis-ball size. 

A row of cauliflowers will often mature all at the same time, leading to a glut. So it’s best to start harvesting before they reach full size, to spread the crop over a longer period. 

To harvest, cut the stem with a knife, taking the head and a few of the leaves beneath it, to protect the curd.  

Cauliflowers are best eaten fresh, but can be stored in a fridge for a few days – they keep better with a few leaves intact. Cauliflower florets can also be blanched then frozen. 

To prepare a cauliflower, cut the head into smaller florets, removing the toughest stems and slicing up smaller stems, so everything cooks evenly. Then steam, stir-fry, sauté or bake. Cauliflower is great in soups, stews and other hearty dishes, including classic cauliflower cheese. To make low-carb cauliflower ‘rice’, grate the head or whiz in a processor. Or enjoy the florets raw with a dip or in salads. 

Varieties with orange, purple or green heads generally keep their colour when cooked, although boiling can fade purple heads.  

Cauliflowers are rich in fibre and many beneficial nutrients, including antioxidants and vitamin C. Additionally, purple cauliflowers contain beneficial anthocyanin and orange heads are rich in carotenoids.

Cauliflowers have a reputation for being tricky to grow successfully, but they should be fine if you take care to provide the right growing conditions – firm, fertile soil and consistent moisture – and protect plants from brassica pests and diseases.

Providing good growing conditions:  

• Deformed or button heads or premature bolting (flowering) can be caused by various conditions that lead to a check in growth, including root disturbance due to transplanting too late, loose soil or not firming transplants in securely, irregular or insufficient watering, cold temperatures in spring, hot weather in summer 

• Discoloured heads – protect the developing curds from sun and frost, which can turn them yellow or brown, by folding the leaves over the head and tying in place with string if necessary. 

Protecting cauliflowers from brassica pests and diseases: 

• Cover the crop at all times with insect-proof mesh or fleece, supported on canes, and put brassica collars around the base of plant stems – this will protect them from most brassica pests, including cabbage caterpillars, cabbage root fly and pigeons 

• Protect seedlings and young plants from slugs and snails, and keep watch for aphids and whitefly, removing them before they multiply 

• Deter clubroot disease by applying lime if you have acidic soil, to raise the pH to at least 7.5. If clubroot has been a problem in the past, start cauliflowers off in pots, ensuring they’ve developed a strong root system before you transplant them into the ground.