Growing Brussels Sprouts in Scotland: The Complete Guide

Brassica oleracea (Gemmifera Group)

Everything you need to grow Brussels sprouts in Scotland, from a February sowing on a windowsill to sprouts sweetened by frost on a December morning. We have done the research so you don't have to.

Brussels sprouts are the slowest crop in the vegetable garden. Sow them in February and you will be harvesting them at Christmas. They occupy the ground for most of the year, they grow tall enough to catch the wind, and they are a brassica, which means they inherit the full pest list. But they are one of the very few crops where a Scottish winter is an advantage. Frost converts the plant's starches to sugar, and a sprout cut after a hard Scottish frost is sweeter and nuttier than anything you will buy. A properly grown crop will stand through December, January and into February, giving you fresh vegetables when the shops are selling imports and your other beds are frozen.

Why Brussels sprouts suit Scotland

This crop wants what Scotland has: a long cool growing season and a frosty finish. Sprouts outright have the sweetest flavour when harvested after being frosted. The cooler the autumn, the better the eating. A Scottish garden gives the plant time to develop its tall sturdy stem through summer, then delivers the cold that turns the starches to sugar in November and December.

Our climate also holds down two of the difficult brassica pests. Cabbage aphid and cabbage root fly are less troublesome here than further south. The plants mature more slowly than they would in England, but a brassica that matures slowly in a cool summer is a brassica that forms tight, firm sprouts rather than loose open buttons.

Varieties

Cascade and Crispus are club root resistant, worth having on Scotland's naturally acidic soils, where liming is the usual remedy. Stack a resistant variety on top of that and you have covered the risk twice. These hold the RHS Award of Garden Merit, a UK-wide award rather than a Scottish one.

Also worth considering

Soil and site

Brussels sprouts want a sunny spot with fertile, well-drained, firm soil. Choose a sheltered position. These plants grow about 90cm tall on a single stem, and a winter gale on an exposed Scottish plot will loosen them at the roots or snap them entirely.

If your soil is very acidic, apply lime the winter before sowing to raise the pH to at least 6.5 and deter club root disease. This matters more in Scotland, where naturally acidic soils are common. A simple soil test kit will tell you whether liming is necessary.

Dig in two bucketfuls of well-rotted manure or garden compost per square metre, ideally the previous autumn, so the ground can settle over winter. Sprouts need firm soil to form tight buds. If you are adding compost just before planting, tread the ground down firmly before putting the plants in. Loose soil means loose sprouts.

Sowing and planting

Brussels sprouts need a long season. Start them early. Sow indoors from February to April in modular trays, two seeds per module, 2cm deep, in a greenhouse or on a bright windowsill. Germination takes about two weeks. Thin to the strongest seedling per module and keep them in good light. Sowing in modules also helps if you have club root in your soil. A well-developed root system before going into the ground means the plant is less severely affected.

For outdoor sowing, sow from early March to May into prepared ground. Sow seeds thinly, 2cm deep, in rows 15cm apart. Thin seedlings to 7.5cm apart, removing the weaker ones. At their final spacing, transplant young plants or thin to 60cm apart with 60cm between rows. Sprouts need wide spacing. Cramped plants produce loose open sprouts and fungal diseases move in faster.

Plant out indoor-raised or seedbed-grown plants in late spring or early summer, when they are 10 to 15cm tall. Harden off indoor-grown plants first. Set each plant in its hole more deeply than it was in the pot, with the lowest leaves at the soil surface. Firm in well and water generously. Cover with insect-proof mesh from the start.

Watering and care

Water young plants regularly. Never let the soil dry out while they are establishing. Once the plants are growing strongly, you should only need to water during prolonged dry weather. A thick mulch of well-rotted manure or garden compost around the plants holds moisture and suppresses weeds.

Weed regularly while the plants are young. Once the crop is tall and leafy, it shades out most competition. Remove any yellowing or faded lower leaves to keep good airflow around the plants, which helps deter fungal diseases.

If your soil is poor, apply a nitrogen-rich fertiliser in June or July to boost growth before the sprouts begin to form.

Support: in late summer, mound soil up around the base of the stems to increase stability. Taller plants may need staking with a sturdy bamboo cane, especially on exposed sites. A top-heavy sprout plant caught by an autumn gale can loosen its roots enough to stop cropping entirely. Do this before the wind arrives.

Protection: cover the crop with insect-proof mesh, supported on canes and pinned to the ground. Cabbage white butterflies, cabbage root fly and pigeons will all take a sprout plant if it is not covered. The mesh stays on for the life of the crop. It is cheap and it removes the daily patrol for caterpillars.

Harvesting

Early varieties can be ready from autumn onwards, but the main crop comes through winter. Harvest when the sprouts are about the size of a walnut, firm and still tightly closed. The flavour is sweeter after a frost. Start with the lowest sprouts on the stem and work upwards. Snap each sprout off with a sharp downward tug, removing the leaf below it at the same time. Take a few from each plant across the row rather than stripping one plant bare.

With newer varieties, the sprouts mature more uniformly. You can cut the whole stem if you prefer, then either stand it in water for a few days or hang it in a cool frost-free shed and pick sprouts as needed. Once cropping is finished, the mild-flavoured young leaves at the top of the plant, called sprout tops, can be harvested too and cooked like spring greens.

A Brussels sprout plant standing through a Scottish December, sprouts tight and bright against the snow, is one of the most dependable things a winter garden produces.

Common problems

• Club root causes swollen, distorted roots. Plants wilt in dry weather. Lime the soil to raise pH above 6.5, start plants in modules to give them a head start, and rotate brassicas. No chemical treatment exists. Cascade and Crispus carry genetic resistance.
• Cabbage caterpillars are the larvae of cabbage white butterflies. They can strip a plant in days. Cover with insect-proof mesh from the start. If they get in, pick them off by hand.
• Cabbage root fly maggots eat the roots. Mesh is the defence. Less troublesome in Scotland's cool summers.
• Pigeons will strip a sprout plant to the stem. Mesh or netting, from the day you plant out.
• Loose open sprouts usually mean the soil was too loose or the plants were too close. Firm the ground before planting. Keep to the full 60cm spacing. F1 hybrid varieties form tighter sprouts more reliably.
• Plants blowing over means the ground was too loose, no soil was mounded around the stems, or the plants were not staked. An exposed Scottish plot tests all three. Do them before the autumn gales arrive.

Common questions

Sources