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 (UK):
- Autumn (Oct–Nov): Sow hardy varieties like ‘Aquadulce Claudia’ for an early summer crop.
- Spring (Feb–April): Sow directly or in modules for transplanting.
- Under Cover: Sow from October to April, depending on your tunnel conditions.
Sowing Broad Beans – Step by Step:
- Sow seeds 5cm deep, 15–20cm apart in rows spaced 40–45cm.
- Sow broad beans with the black scar facing down — it’s the root end.
- Use root trainers or deep pots if starting in modules.
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?
Most varieties reach 90–120cm. Dwarf types (e.g. ‘The Sutton’) stay under 60cm and suit smaller tunnels or containers.
Can You Grow Broad Beans in Pots?
Absolutely. Choose a large, deep container and stake them well. Use multipurpose compost mixed with garden soil for structure.
Companion Plants for Broad Beans
Broad beans work well alongside:
- Salad leaves – make the most of early tunnel space
- Brassicas – share similar cool-season preferences
- Herbs like coriander or dill – attract beneficial insects
Avoid planting next to onions or garlic, which can stunt legume growth.
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 hoverflies.
- Chocolate spot: A fungal disease. Avoid overcrowding and overwatering. 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 to Harvest Broad Beans
- Broad bean harvest time: Usually 12–16 weeks after sowing.
- Pick when pods are well-filled but still tender — before they turn tough and mealy.
- When to pick broad beans: If you can feel the shape of individual beans through the pod but they’re not bulging, they’re just right.
- Harvest regularly to encourage more pod development.
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
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