Fothergill's Growing Guide: Broccoli

Average time to harvest calabrese

16 weeks

Average time to harvest sprouting broccoli

40 weeks

Sowing depth

1.5cm

Soil type

Well cultivated, fertile soil

If you’re wondering how to grow your own broccoli, you’re in the right place. From seed to harvest, growing your own vegetables is so rewarding and genuinely exciting. It’s something to enjoy, an excuse to get outside, put your hands in the dirt, and be present in the moment.

At Fothergill’s, we believe there’s a budding gardener in us all, and this guide will show you just how easy it is.

Let’s get into it.

Did you know?

There are two main types of broccoli: sprouting (Brassica oleracea Italica) and calabrese (Brassica oleracea Botrytis).

The word Broccoli originates from the Italian word broccolo, which means ‘the flowering crest of a cabbage’. It’s a floret made up of countless little flowers. A member of the brassica family, which also includes cauliflower and cabbage, it’s been eaten by the Italians since ancient times. However, it wasn’t until a royal French-Italian marriage in 1533 that broccoli was introduced to the rest of Europe, and it didn’t become popular in North America until the early 1920s when it was bought over by Italian immigrants.

Broccoli can be eaten raw, boiled, fried, or steamed. It contains more Vitamin C than an orange, as well as high levels of vitamin A and antioxidants.

Growing at a glance

Broccoli grows best at an average mean temperature of below 15°C, so it’s ideal for a UK climate. Ideally, grow them in a sunny, sheltered spot.

Sprouting broccoli can be sown indoors from February to July, while calabrese can be sown indoors from March to April. It’s better to start broccoli off indoors due to the pests and unpredictable late frosts.

Once plants are 10-15cm high, they can be planted out into their final growing positions in a well-cultivated bed. Ensure you net the plants straight away to deter pests.

Water regularly, and apply a nitrogen rich plant feed, if necessary, once the heads start to form.

Broccoli should be harvested once the heads are well formed but before the individual flowers begin to open.

Always rotate brassica crops. If possible, grow them in a different location each year, to reduce the chance of soil borne diseases building up.

Sowing seed

Use a standard or modular seed tray and fill with a seed compost mix. Tamp the soil down to create a firm surface, then sow thinly. For modular trays create a 0.5cm hole in the centre. Place two seeds in the hole and cover over with compost. Water in well and place the tray in a greenhouse, cold frame or on a windowsill to germinate.

Germination should occur within 14-28 days, or slightly faster if you’re using a heat mat, heated greenhouse or heated propagator. Once they’ve germinated, give them plenty of light so they don’t become leggy.

Depending on the variety, direct sowing broccoli into its final growing area (or into a separate seed bed) can be done from late March when the soil is warmer and more workable. Prepare the open growing area by adding plenty of organic matter and working it into the soil. Firm the soil down with the back of a rake, or use your heels to walk over the growing area, and then create a fine level tilth. Water the area before sowing to avoid dispersing the seed.

For seed beds, create drills 1cm deep and 15cm apart. Rows should be 45cm apart if you’re sowing directly. Sow seed thinly, then cover over with fine soil. Again, germination should take between 14-28 days. If sowing early in the growing season, a cloche or horticultural fleece may be needed to protect the sown area.

Pricking out

Once seedlings are firmly established, to avoid disturbing the roots, either pinch-out the weaker seedling or cut it away. Keep the soil moist.

For seedlings directly sown, thin them out to 45cm apart. Keep the soil moist.

Hints and tips

Once you’ve harvested the main head of the calabrese, leave the remaining plant in the ground. It will produce smaller side shoots, giving you a second crop.
Broccoli is best steamed as it retains both flavour and texture better.
Calabrese has a milder flavour compared to other broccoli types.

Growing on

Once indoor seedlings are 10-15cm high, they are ready to be planted out into their final growing positions. Before planting out, let them harden off outside for a week beforehand by bringing your plants outside for a few hours every day so they can acclimatise to outside conditions.

The growing area should be prepared with plenty of organic matter worked into the soil, adding a general-purpose fertiliser, if necessary. Ideally, the area should be in a warm, sunny, sheltered position. As broccoli can get quite tall, plant deeply (up to its first set of leaves) and firm around the roots. This will help it establish a good root system and prevent wind rock. Plants should be spaced 45cm apart in rows 45cm apart. Water in well. This also applies to plants that were grown and lifted from a seed bed.

Plant maintenance

Water regularly throughout the growing season, ensuring the soil never dries out, and keep the area weed-free. If you prepped your growing bed correctly, it won’t need additional fertiliser. Otherwise, give your crop a high nitrogen plant feed once the heads start to form.

Jargon busting

Germination
When a seed begins to grow and its first shoot appears.

Propagator
A covered, typically heated container filled with compost, used for raising seedlings.

Pinch Out
A form of pruning, using forefinger and thumb, to remove a soft stem, encouraging plants to become bushier.

Pricking Out
Removing seedlings from growing trays and planting them into individual pots to grow on.

Tilth
Surface soil which is fine and crumbly.

Drill
A shallow trench in the ground, for seeds to be sown in.

Common problems

Birds (especially pigeons) and caterpillars will happily eat the leaves of the plants, so place fine netting over the crop at the time of planting. This will also deter the white cabbage butterfly from landing on the plants to lay its eggs during the summer months; an infestation of caterpillars can quickly devastate a crop.

Cabbage root fly larvae feed on brassica roots. When planting into its final growing position, place a brassica collar around its stem, just above the soil. This will help prevent cabbage root fly from laying eggs at the base of the plant, and its hatched larvae from eating and destroying the roots.

Club root is a fungal infection that damages the roots, leaving them swollen, distorted and stunted. The foliage can also discolour. If plants are infected, remove from site and destroy. Wash hands, tools and boots to help prevent the spread of infection. Avoid planting brassicas in areas where club root has occurred. Buy seed varieties that have some degree of club root resistance.