Broad beans — also known as fava beans — are one of the earliest crops you can sow, and one of the most satisfying to harvest. Packed with protein, pollinator-friendly, and surprisingly cold-tolerant, they’re a staple of early-season growing under cover. Whether you’re sowing in autumn for an early crop or starting fresh in spring, they’re easy to grow and even easier to enjoy.
What Are Broad Beans?
Broad beans (Vicia faba) are a cool-season legume grown for their plump, edible seeds and nutritious young shoots. Popular in traditional British allotments and Mediterranean kitchens alike, they’ve earned a reputation for being easy to grow, even in tough conditions. In a polytunnel, they get a head start on the season — ideal for early harvests or extending your spring cropping window.
Why Broad Beans Thrive in a Polytunnel
Broad beans are famously hardy, but a polytunnel gives you the edge. Sowing under cover in autumn or early spring protects young plants from harsh weather and ensures strong early growth. Plus, you’ll benefit from:
- Faster germination in warmer soil
- Reduced wind damage (especially important once they flower)
- Earlier harvests than outdoor sowings
- Better pollination control, or a chance to hand-pollinate if needed
Even in cooler tunnels, they’ll keep growing steadily, setting pods before most other crops are ready to go in.
How to Grow Broad Beans
When to Sow Broad Beans in the UK
Broad beans are one of the hardiest crops you can grow, and timing your sowing is key to strong harvests.
- Spring sowing: Sow outdoors from March to May once the soil begins to warm.
- Autumn sowing: In milder parts of the UK, sow in October–November for an early crop the following spring. Under a polytunnel, autumn sowing is much more reliable, giving young plants shelter through winter.
- Under cover: Sow seeds indoors in modules from February to get a head start and transplant outside once conditions improve.
How to Plant Broad Beans (Spacing & Depth)
Correct spacing helps broad beans grow strong and reduces the risk of disease.
- Depth: Sow seeds about 5–7cm deep.
- Spacing: Plant seeds 20cm apart in double rows, leaving 45cm between rows. This layout helps support plants and improves airflow.
- Soil prep: Broad beans prefer well-drained, fertile soil enriched with compost.
Broad Bean Plant Spacing:
Give them room, air circulation reduces disease and supports pollination.
Do Broad Beans Need Support?
Yes, especially in tunnels where airflow is limited. Use canes, string, or mesh to prevent plants from flopping once pods form.
How Tall Do Broad Beans Grow?
Broad bean plants typically reach 90cm to 1.2m tall, depending on the variety. Dwarf varieties stay shorter, while heritage or tall types can grow even higher. In exposed sites, use canes and string to provide support and prevent plants from toppling over in strong winds.
Broad Beans in Containers: Can You Grow Them in Pots?
Yes — broad beans can be grown successfully in large pots or containers, making them a good choice for small gardens, patios, or balconies.
- Choose a container at least 30cm deep with good drainage.
- Space plants about 20cm apart in the pot.
- Water regularly, as pots dry out faster than soil beds.
- Support taller plants with canes or a wigwam structure.
Container-grown broad beans may produce slightly smaller harvests, but they’re still a rewarding option.
Companion Planting with Broad Beans
Broad beans are excellent team players in the garden. They fix nitrogen in the soil, enriching it for future crops. Good companions include:
- Garlic (Crop Spotlight: Garlic), which helps deter pests.
- Spinach and lettuce, which grow well in the shaded spaces between bean rows.
- Avoid planting near onions or leeks, which compete for nutrients.
Broad Bean Pests & Problems
Even under cover, a few common problems may crop up:
- Aphids (especially blackfly): Pinch out soft tips once flowers set to deter them. Encourage ladybirds and hover flies.
- Chocolate spot: A fungal disease. Avoid overcrowding and over watering. Ventilate your tunnel well.
- Poor pod set: If your tunnel is fully enclosed, hand-pollinate flowers with a soft brush or give plants a gentle shake.
When Are Broad Beans Ready to Harvest?
Broad beans are usually ready to pick 12–16 weeks after sowing, depending on the variety and conditions.
- Harvest pods while the beans inside are still small and tender — about the size of a fingernail — for the sweetest flavour.
- If you prefer larger beans, leave pods to swell, but don’t wait too long as they can become tough.
- For an extended season, pick pods regularly to encourage further production.
Tip: Young pods can even be eaten whole, much like mangetout.
Autumn Sowing for Early Crops
If you don’t want to wait until summer for your first harvest, try autumn sowing. Broad beans sown in October or November can overwinter and give you an extra-early crop in May. Protecting them with a polytunnel or fleece makes this method far more reliable, especially in colder regions.
How to Use Broad Beans
- Young pods: Eat whole when finger-length (like mangetout).
- Fresh beans: Shell and boil, or double-pod for a softer flavour.
- Shoots and tips: Edible and delicious raw or wilted in butter.
- Dried beans: For winter stews, hummus, or long-term storage.
Final Tips
- Sow in succession for a longer harvest window.
- Pinch out tops once pods start forming to prevent blackfly and encourage bigger beans.
- Leave roots in place after harvest, they fix nitrogen and improve soil health.
- Consider dwarf varieties if height is a limitation in your tunnel layout.
Further Reading
- RHS Guide: How to Grow Broad Beans
- EasyBuild Polytunnel – Ideal growing space for herbs and companion plants
EasyBuild: Design Your Polytunnel in Minutes!
Thinking of getting a polytunnel? Don’t just take our word for it, try the EasyBuild Configurator and compare for yourself.
We built EasyBuild to make polytunnel growing easier, tougher, and better value. Looks like it worked.
Sow broad beans outdoors from March to May, or in October–November in milder areas. For earlier crops, start them under cover in February.
Plant broad beans about 20cm apart in double rows, leaving 45cm between rows. This spacing gives good airflow and helps plants support each other.
Yes — broad beans grow well in containers at least 30cm deep. Space them 20cm apart and keep them well-watered, as pots dry out quickly.
Most broad bean plants reach 90cm to 1.2m tall, though dwarf types are shorter. Taller varieties may need staking or string supports.
Broad beans are ready 12–16 weeks after sowing. Pick pods when beans are fingernail-sized for the sweetest flavour, or let them swell for bigger beans.
