How to Grow Cauliflower

Growing your own cauliflowers allows you to try out many different flavours and colours from different cultivars that are vastly superior to shop-bought heads. Though commonly associated with the colour white, you can in fact grow these vegetable seeds and vegetable plants in vibrant purples, greens, and oranges too. They’re also packed with vitamins, minerals, fibre and antioxidants, making for a delicious and nutritious addition to your plate.

Cauliflowers are known for being a challenge to grow. There mustn't be a check to growth, so careful planting and watering are essential. If successfully grown, you’ve officially made the mark as an expert gardener! To find out how to grow cauliflower and learn our expert tips, read our guide below, which contains all of the information you need to know.

Cauliflower plants should be grown in a sunny spot to ensure healthy growth and provide the conditions needed for the perfect large, compact heads.

You'll need a rich and deep soil with added well-rotted manure or garden compost, that is also moist but free-draining. It’s better if the soil has been manured for a previous crop, as this means that the ground will have had time to settle. Cauliflowers are hungry plants, so soil fertility is important.

You should avoid planting your cauliflowers in a spot where you’ve grown brassicas within the past two years, as this can lead to your plants developing diseases.

Cauliflowers prefer slightly alkaline soil, so add some lime soil conditioner if your soil is more acidic. Ideally, this should be done the previous winter. 

Before growing outdoors, they will benefit from soil that has had any weeds thoroughly removed, been firmed in by treading and had high potassium fertiliser added. In particular, brassicas such as cauliflower require well-firmed soil.

When to Sow Cauliflower Seeds

The main sowing period for cauliflower seeds is March to May, although early crops can be achieved by sowing under glass in January or sowing a variety like Orkney F1 in the autumn.

How to Sow Cauliflower Seeds

Sowing Cauliflower Seeds Indoors

Sowing your cauliflower seeds indoors rather than outdoors is often preferable for gardeners, as this allows you to better control temperatures and prevents various pests from attacking your seedlings. This can be in a greenhouse or on a sunny windowsill.

Sow your cauliflower seeds in seed trays, ensuring that they are watered regularly and receive a good amount of light. They should be sown with one seed per module, in moist, multi-purpose compost. These should be grown between 12 and 22°C. Providing these conditions, your seeds should germinate at around two weeks after sowing.

At around six weeks after sowing, when their roots have filled the module and if all risk of frost has passed, you can transplant your seedlings outside.

Sowing Cauliflower Seeds Outdoors

Cauliflower seeds are best sown indoors and later transplanted outside, though they can be sown outdoors if preferred. In this case, you should sow your seeds thinly at around 2cm (¾in) deep. Once they start developing, thin your seedlings out to provide around 60cm (24in) between them, as this prevents any checks in their growth from overcrowding. However, you should check your seed packet in case spacing requirements are different for your chosen variety.

When to Plant Cauliflower Plants

Cauliflower plants are generally best planted out between May and July when they are around 10-15cm (4-6in) high. This shouldn’t be delayed, as plants that have had their roots disturbed at a later stage are more likely to bolt.

How to Plant Cauliflower Plants

Before planting out your cauliflower plants, they should first be gradually hardened off over the course of a couple of weeks to acclimatise them to outdoor conditions. They should be planted in soil that has been prepared as described in the ‘Ground Prep’ section and thoroughly watered prior to and after transplanting to prevent checks to growth.

To transplant your cauliflowers, make a hole with a trowel that’s deep enough to ensure that their leaves are at ground level. Then, carefully place your plant in the hole, avoiding disturbing the roots, and ‘puddle in’ (repeatedly fill the hole in with water) to ensure the ground is moist. After this, firm the soil around your plants in especially well.

Your plants will need to be spaced depending on what varieties you’re growing. Specifically, you should space summer and autumn cropping varieties 60cm (2ft) apart, winter varieties (75cm) (30in) apart and space 30-45cm (12-18in) apart to produce mini, 'one person' curds. You should expect to produce one cauliflower head per plant.

Giving your cauliflowers a good amount of space ensures that they will grow to be of larger size and prevents any problems arising from poor circulation or shading. The only exception is mini cauliflowers, which are deliberately planted closer together for smaller growth.

Watering

Ensuring you water your cauliflowers regularly and avoid drying them out is key to their success. You should water your cauliflowers to keep the soil moist, though not so much so that the soil is waterlogged. This should generally be done every week to two weeks, while plants should be regularly watered once curds start to form.

Watering your cauliflowers during dry weather is especially important. Water more frequently during these periods, ensuring that their roots are thoroughly wet.

Feeding

Once your plants are established, feed occasionally (roughly every fortnight) with a high-nitrogen feed to encourage growth.

Mulching

Add a good layer of organic mulch to your soil, such as well-rotted manure or garden compost, as this will help to prevent weed growth and retain moisture. Leave a small gap around the base of the stem when you do this to prevent diseases and ensure good air circulation. 

Weeding

Your soil should be regularly weeded to prevent your cauliflowers from competing for resources with other plants.

Protection from Sun

Protect the curds of summer varieties from the sun by bending a few leaves over them. Doing the same with winter varieties will protect against frost. This is particularly important with the less hardy romanesco types, such as Natalino.

When to Harvest Cauliflower

When you harvest your cauliflowers will be dependent on various factors, such as when you sowed them, weather conditions and their variety and size. Generally, cauliflowers will be ready to harvest from three to six months after sowing.

How to Harvest Cauliflower

You should start cutting your cauliflower heads when they are firm, compact and of a good size. Check your seed packet if you’re unsure as to what size you should harvest at for your chosen variety. White varieties should be harvested before their curds turn yellow, and mini varieties should be harvested once they’re around the size of a tennis ball.

You shouldn’t wait too long for harvesting, however, as their florets separating is a sign that it’s now too late, as they will have a bitter taste.

To harvest your cauliflowers, cut the stem to take the whole head and some leaves beneath it for protection. 

Cauliflower is best eaten fresh. However, by lifting the plants and hanging them upside down in a cool shed, they can keep for up to three weeks. Just be sure to mist the curds frequently to prevent drying out.

Cauliflowers are known to be a little tricky to grow, though you will produce great heads if you keep on top of your plants’ requirements regularly. They can be known to encounter some problems, which are best prevented or resolved using the methods below:

Birds - Protect your plants from bird attacks by covering with garden netting or fleece.

Frost - If a frost is predicted, you should cover your cauliflowers with garden cloches or fleece, as this can lead to bolting, which diverts energy away from growing curds.

Pests - Various pests can attack cauliflowers, such as cabbage root fly, slugs, snails, and cabbage caterpillars. These can be protected from with a variety of measures, such as garden fleece, slug and snail control products and cabbage collars.

Clubroot - Clubroot is a disease that leads to severely distorted and swollen roots, leading to poor nutrient and water absorption and poor growth. The best way to deal with clubroot is using preventative measures, such as buying disease-resistant vegetable seeds, growing seeds from trusted providers and practising good garden hygiene. For more information on clubroot, read our guide on how to prevent clubroot disease.

Bolting/deformed heads/button heads - These problems can arise as a result of a check in growth, such as irregular watering, experiencing particularly cold or hot temperatures, root disturbances as a result of transplanting your plants too late or any other irregularities. Providing your cauliflowers with consistently suitable conditions will prevent these problems from occurring.

Discoloured heads - Your cauliflowers may experience discoloured heads, which can occur as a result of exposure to the sun or a frost. This can be prevented by covering the heads using their leaves, which you can tie in place to keep secure with string if needed. 

This guide contains everything you need to know about how to grow cauliflower, so all that’s left is to get some quality seeds or plants. In our huge selection of gardening supplies, you can find cauliflower plants and cauliflower seeds in unique cultivars for distinctive flavours and colours in addition to healthy growth. Having over a century of experience, you can trust these to deliver on quality for reliably growing and delicious produce from D.T. Brown.

You can find out how to grow many other vegetable seeds and fruit seeds, by finding our various other growing guides and useful blogs on our garden blog. You can also take a look at our guide on how to grow brassicas for more general tips, where you can find our many other brassica growing guides.

If you’d like to know anything more about our collection of fruit plants, herb plants, garden accessories, or anything else you can find in our shop, get in touch today and a member of our team will get back to you as soon as possible.