Horticulture Magazine

How To Grow Brussels Sprouts

brussels sprouts and cabbage plants growing in wooden planters

Gemmifera Overview

Official Plant NameBrassica oleracea var. Gemmifera
Common Name(s)Brussels Sprouts
Plant TypeVegetable
Native AreaCultivated
Hardiness RatingH4-H5
ToxicityEdible
FoliageLarge, green (edible) leaves
When To Sow IndoorsMarch, April
Plant OutMay, June
Harvesting MonthsJanuary, February, March, September, October, November
Sunlight

Preferred
Full Sun or Partial Shade

Exposure
Sheltered

Size

Height
0.5 – 1M

Spread
0.1 – 0.5M

Soil

Preferred
Most Soil Types

Moisture
Moisture Retentive

pH
Any (except highly acidic)

Brussels sprouts are one of those vegetables people either love or loath.

But for many, either way, they are considered an integral part of the traditional Christmas dinner. And can be a useful part of the diet over the coldest part of the year. Like many other brassica crops, they can be a great addition to a home grown diet. And are a good choice for those who want to grow their own all year round.

Brussels sprouts are, admittedly, not the easiest brassica crop to grow. But they are a vegetable that even novice gardeners can take on. As long as you remember a few basic things, you should find that you are able to grow this crop successfully, wherever you live in the UK.

Background & Origins

a large field of brussels sprouts plants
Brussels sprouts.

Brussels sprouts are a leaf vegetable in the Gemmifera group of cabbage family plants (Brassica oleracea). As such, they are Brassicaceae (brassicas), also known as cruciferous vegetables.

They have long been popular in Brussels, Belgium, from which city they take their name.  And it is believed that they were cultivated there from around the 13th Century.

Forerunners of these plants first appeared in cultivation ancient Rome and may have appeared in northern Europe in around the 5th Century. These brassica crops in their modern form and appearance, however, took off in Belgium, and spread to other areas of Northern Europe which have the temperature ranges ideal for their cultivation.

Brussels sprouts can grow at any temperatures between around 7 and 24 degrees c. But highest yields can be achieved at temperatures of around 15-18 degrees. Typically, Brussels sprouts are harvested and eaten between September and March.

Brussels sprouts are a biennial plant, which completes its lifecycle over two years.

Why Grow Brussels Sprouts in Your Garden?

One of the main reasons to grow Brussels sprouts in your garden is that, like other brassicas or cruciferous vegetables, they are good for you to eat. They provide high levels of vitamin C and vitamin K, and more moderate quantities of a range of B vitamins, essential minerals etc..Like other brassicas, they also contain sulforaphane – a phytochemical which may bring health benefits.

Many people dislike sprouts because they have only tasted them boiled to oblivion. But even those who think they dislike this vegetable may feel differently when they taste roasted sprouts, as cooking them in this way (and not overcooking) brings out their flavour in a different way. You may also be surprised by how much better sprouts taste when picked from the garden rather than being bought at a store.

One of the other main reasons to grow Brussels sprouts at home is that they provide you with fresh home grown vegetables in the coldest and darkest part of the year, when little else is available from an outdoors vegetable plot.

Common Varieties

There are a number of different varietals of Brussels sprouts great for UK gardens. Some good choices include:

  • ‘Brodie’
  • ‘Clodius’
  • ‘Crispus’
  • ‘Doric’
  • ‘Igor’
  • ‘Maximus’
  • ‘Sanda’
  • ‘Red Ball’
  • ‘Red Rubine’
  • ‘Roodnerf’

Some are F1, some heritage seeds. Most are green, though some, as the names suggest, have reddish (or purplish) hues.

close up of purple red brussels sprouts
Purple red Brussels sprouts.

Sowing

Brussels sprouts are a crop that is typically sown in March or early April. Seeds are sown indoors, under cover in a greenhouse or polytunnel, under cloches or in a cold frame. Seeds should be spaced thinly, around 1 -1.5 cm deep. Seedlings should be thinned to at least 7.5cm apart. The seeds will germinate with temperatures as low as 4 degrees C. But germination rates will be highest at temperatures above 7 degrees.

Planting

Your Brussels sprouts seedlings should then be transplanted to their final growing positions between mid-May and early June, when your young plants will be 10-15cm tall, and have around 7 true leaves.

Seedlings should be well watered before they are transplanted, then watered in well after they are placed into your vegetable garden. In most cases, you should aim to space your Brussels sprouts around 60cm apart.

When choosing a location for Brussels sprouts, note that they can thrive in any sunny and sheltered position. They can cope with some light shade, but a sunnier site will provide better yields. Brussels sprouts can cope with a range of different soil types, but will do best in a rich soil, with a neutral to alkaline pH (above 6.5). Acidic conditions can increase the likelihood of problems with club root. Where the soil is affected with club root, growing in containers may be a better option.

Before planting your Brussels sprouts, add plenty of organic matter, such as a home-made compost or well-rotted manure, to the growing area.

When planting, ensure that you firm the soil well around the plants, to make sure the root systems are not damaged by wind rock.

What To Plant With Brussels Sprouts

In an organic garden, it is always best to adopt a holistic and integrated approach. You should consider the different ways in which your crops can be combined and in which additional companion plants can be added to aid the sprouts, and the system as a whole.

Of course, it is common to sow Brussels sprouts in the same bed as other brassica crops. Planting these in the same growing area will make it easier to maintain a crop rotation system and make sure brassicas are not grown in the same bed year after year. Of course, other brassicas like similar conditions, so can grow well in the same area.

Unfortunately, though they can be good companions, brassicas share pests and diseases. This means that it is not a good idea to grow exclusively brassicas in one bed. For integrated pest management in an organic garden, you should grow brassicas alongside other companion crops. Mustard, which is another brassica, can act as a trap crop when grown close by. But for pest management, you should also consider sowing Brussels sprouts alongside, for example:

  • Onions
  • Leeks
  • Garlic
  • Aromatic herbs (mint, thyme, rosemary, sage, dill etc..)
  • Marigolds
  • Nasturtiums
  • Geraniums

Since Brussels sprouts require a wide spacing, and are fairly slow to mature, it also makes sense to companion plant to take up the spaces between your plants as they grow.

Try planting these between your Brussels sprouts to make the most of the space:

  • carrots
  • beetroot
  • radishes
  • celery
  • lettuce
  • spinach

As nitrogen-hungry plants, Brussels sprouts may also benefit from growing legumes – such as peas or French beans, for example, as companion crops.

Avoid planting strawberries close to Brussels sprouts, however, as these two plants are said to affect each other’s growth.

You should also avoid planting Brussels sprouts too close to other heavy feeders, such as squash, sweetcorn, tomatoes, peppers, and potatoes. (And any other members of the nightshade family.)

Plant Care

Watering

Water Brussels sprouts every 10-14 days in dry weather. Water plants at the base, and make sure you have mulched around the plants to retain moisture in the soil, particularly during the warmest summer months.

Fertilisation

As nitrogen-hungry plants, brassicas like Brussels sprouts will benefit from a nitrogen rich organic mulch. And will also appreciate the addition of a high-nitrogen organic fertilizer (such as dried chicken manure pellets, for example) after midsummer. You might also choose to make a nitrogen rich liquid plant feed to give the plants a boost in around July.

Pest Protection

Brussels sprouts, like other brassicas, are susceptible to pests – most common and notable among these are the caterpillars of cabbage white butterflies, and birds. Birds (like pigeons for example) can quickly eat up an entire crop if they are not protected.

It is a good idea to place netting over Brussels sprouts and other brassica, which is sturdy enough to prevent birds from eating your crop, yet has a fine enough mesh to keep off butterflies and prevent them from laying their eggs on your crops from which caterpillars will emerge. Though companion planting will aid with pests to a degree, sometimes a physical barrier will be required.

Support

In around September, it can be a good idea to mound up the earth around your tall Brussels sprout plants, to provide them with a little more support before autumn winds and stormier, wilder weather arrive.

Harvesting Your Veg

grown brussels sprouts ready to be harvested
Brussels sprouts ready to harvest.

Brussels sprouts are usually harvested from September through to March. It is worth noting, however, that Brussels sprouts are one of a number of vegetables which taste better after the first frosts. The cold triggers metabolic processes through which starches break down into plant sugars – so Brussels sprouts that have been exposed to frosts and freezing temperatures will taste a little sweeter than those that have not.

Start by harvesting the lowest sprouts, when they are tightly closed, firm, and around the size of a walnut. Snap each one off with a sharp tug downwards. You can leave the plants standing in your garden and take a few more sprouts as and when they are required over the winter. For greatest nutritional value and taste, you should eat Brussels sprouts as soon after they are harvested as possible.

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