How and When to Plant Broccoli in the UK

From salads to soups, and curries to casseroles, broccoli stands out as a versatile and nutritious vegetable that enhances any dish. Its rich, green florets not only add a burst of colour but also deliver a powerhouse of vitamins, minerals, and fibre, making it a beloved choice for health-conscious cooks and food enthusiasts alike.

For those keen to grow their own, let’s discover when to grow broccoli in the UK to ensure a rich and plentiful harvest! If you want to know how to grow broccoli in the UK, our helpful guide will cover everything you need to know.

The best time to plant broccoli can vary depending on whether you’re starting seeds indoors or directly sowing them into the ground, as well as the specific variety of broccoli. Generally, it’s a cool-season crop, thriving in temperatures between 18°C – 24°C (65°F – 75°F).

If the temperature is too warm, the plants can bolt. This is when a plant prematurely produces flowers and seeds, often due to stress factors like high temperatures or long daylight hours. Bolting – also known as going to seed – usually results in a decline in the quality and taste of the edible parts of the plant.

Indoor Cultivation

If you want to start your seeds indoors, sow them about four to six weeks before the last expected frost. This usually means in late February to early March but with the notoriously unpredictable British weather, it could be even later.

Outdoor Cultivation

Directly sow seeds or transplant young seedlings outdoors once the danger of hard frost has passed, typically from the middle of March to early April.

Early varieties of broccoli can mature and be ready to harvest approximately 50 to 70 days from transplanting, or around 70 to 100 days from seeding if directly sown into the garden. They are developed to produce heads faster and are suitable for an early summer harvest.

Maincrop broccoli varieties usually take a bit longer to mature than early varieties. They typically require about 60 to 80 days from transplanting to reach harvest, or around 100 to 150 days if seeds are sown directly in the garden. These varieties are intended for later summer through to autumn harvests.

Knowing when to sow broccoli seeds in the UK can vary due to weather and your particular location. If you’re looking to get ahead with your planting, there are early varieties of broccoli that are bred to mature faster and can be sown earlier in the season.

Calabrese

Often considered the standard green broccoli you find in supermarkets, it matures quickly and is known for its great flavour.

Express

Known for its fast growth and early harvesting, it offers tender, tasty side shoots and is an excellent source of vitamin C.

Green Magic

A hybrid variety that is resilient and produces early yields. It has a sweet flavour and is incredibly versatile.

Maincrop broccoli takes longer to mature but generally produce larger heads and can be harvested later in the season. Popular maincrop varieties in the UK include:

Belstar

A versatile and fast-growing variety that can be cultivated for both early and maincrop production.

Marathon

Known for producing large, dense heads, having a long cropping season and its ability to do well in most soil types.

Ironman

A newer variety known for its high yield, outstanding flavour and disease resistance.
Now you know when to grow broccoli in the UK and the different types, let’s find out how to grow it.

When we’re discussing how to grow broccoli in the UK, most gardeners will know it’s relatively easy to cultivate. Here’s an easy step-by-step guide to get you started.

Choose Your Broccoli Variety

Opt for a variety that’s well-suited to the UK climate, and especially your local region. Early varieties are good for a shorter growing season, while maincrop varieties generally develop larger heads and can be harvested later in the season.

Prepare Your Soil

Broccoli prefers well-drained, fertile soil in sun or light shade with a pH between 6 and 7. Around six to eight weeks before sowing or planting, work plenty of organic matter, such as compost or well-rotted manure, into your planting beds. The plants can get quite tall so try and position them in a sheltered spot where they won’t get buffeted by strong winds.

Sowing Broccoli Seeds

Indoors:

Start seeds indoors 4-6 weeks before the last expected frost date. Use seed trays or pots with seed starting mix. Keep the soil moist and provide plenty of light.

Outdoors:

Directly sow seeds in the garden from mid-March to early April for a summer crop. Plant seeds 1 cm (0.5 inch) deep, spacing them about 7.5 cm (3 inches) apart, in rows that are 30 cm (12 inches) apart.

Transplanting Seedlings:

Transplant indoor-started seedlings outdoors when they have 4-6 true leaves, usually about 4-6 weeks after sowing, ensuring the risk of frost has passed. Harden them off by gradually acclimatising them to outdoor conditions over a week before transplanting. Space the broccoli plants 45 – 60 cm (18 – 24 inches) apart in rows that are 75 cm (30 inches) apart.

Plant Care

Keep the soil consistently moist but not waterlogged. Watering is crucial as the plants grow and especially once they start forming heads. After you’ve transplanted them, you can add a nitrogen-rich fertiliser to encourage growth. To retain moisture and to suppress weeds, add a layer of mulch around your plants. If you do spot weed growth, either remove them by hand or use a garden hoe, but be careful not to disturb the plant roots. Keep an eye out for common pests such as caterpillars and aphids and if you notice an influx of birds and butterflies, you can protect your plants with netting.

Harvesting

Harvest your plants when the head is well-formed but before the flowers start to open. Early varieties can be ready in 50-70 days from transplanting, and maincrop varieties in 60-80 days. If you’ve sown the seeds directly into the ground, maincrop harvesting can be extended to between 100 and 150 days, but specific timings can vary based on the variety and local growing conditions.

End of Season

After harvesting the main head, leave the plant in the ground. Many varieties will produce smaller side shoots that can be harvested later. Once the plants stop producing, remove it from the bed to prevent disease and pest buildup and add them to your composting pile.

Knowing when to plant broccoli in the UK and how to grow broccoli can be a rich and rewarding experience. By sowing broccoli at the right time of year and following our helpful guide for planting, care and harvesting, you can enjoy a bounty of beautiful broccoli.