Looking to bring pollinators into your polytunnel and add a splash of colour while you’re at it? Borage might just be your new best friend. With vivid blue flowers, edible leaves, and a tendency to thrive on neglect, this low-maintenance herb is one of the most rewarding additions to any tunnel setup. It’s tough, useful, and beautiful, and once you plant it, it often comes back year after year with no extra effort.
What is Borage?
Borage (Borago officinalis) is a fast-growing, annual herb native to the Mediterranean. Often grown for its striking star-shaped blue flowers and cucumber-scented leaves, it’s as attractive to beneficial insects as it is to the eye. While often found on the fringes of veg patches or flower borders, borage has huge value under cover too.
It’s also packed with uses. The flowers are edible and decorative, the young leaves can be used in salads or drinks, and the whole plant makes excellent compost fodder.
Why Borage Thrives in a Polytunnel
While borage is hardy and can grow outdoors easily, it excels in a polytunnel. The warmer microclimate encourages quicker growth and a longer flowering season, from early spring right into autumn. That extended bloom time means more visits from pollinators like bees and hoverflies, which in turn benefits your fruiting crops.
It’s also fairly drought-tolerant once established, and thanks to its deep taproots, it pulls nutrients from deeper soil layers, essentially mining goodness for neighbouring plants.
How to Grow Borage
- When to sow: From March to May direct into tunnel beds, or start under cover 4–6 weeks before the last frost.
- Germination: Quick! Usually 5 to 10 days in warm soil.
- Spacing: 30–40cm apart. Borage gets big, and it sprawls.
- Soil: Not picky, but does best in well-drained soil with moderate fertility.
- Watering: Moderate. Let it dry a little between waterings.
- Maintenance: Minimal. Pinch out the growing tips if you want bushier growth. Otherwise, just let it do its thing.
In fact, one of the easiest ways to grow borage is to let it self-seed. It will pop up each year with very little encouragement
Companion Plants for Borage
One of borage’s greatest strengths is its companionship. It attracts bees, parasitic wasps, and other beneficial insects that help pollinate and control pests.
It pairs particularly well with:
- Tomatoes – attracts pollinators, may help deter tomato hornworms
- Strawberries – traditionally thought to improve flavour and yield
- Squash & Courgettes – enhances pollination
- Cabbage family crops – helps distract pests
Common Pests & Problems
Borage is generally trouble-free. That said, under cover, keep an eye out for:
- Aphids – occasionally cluster on new growth but rarely become an issue thanks to predatory insects it attracts.
- Powdery mildew – if airflow is poor or watering is irregular. Thin out plants or space them well to avoid this.
- Self-seeding – which can be a blessing or a nuisance, depending on your view.
How to Use Borage
- Flowers: Use fresh in salads, freeze into ice cubes for drinks, or garnish cakes and cocktails. Their light cucumber flavour is subtle but refreshing.
- Leaves: Best harvested young. Add to salads, yoghurt sauces, or chilled drinks. (Note: leaves become hairy with age, which some people find unpalatable.)
- Green manure: Chop and drop older plants for nutrient-rich mulch. The plant is a dynamic accumulator, especially good for potassium and calcium.
- Bee-magnet: Let some plants flower freely to keep pollinators visiting your tunnel all season.
Final Tips
- Borage can get top-heavy. If you’re growing it near the edge of a bed, give it some support or plan to chop it back mid-season.
- Regularly deadhead if you want continuous blooms, but allow a few to go to seed if you want it to return next year.
- While young leaves are edible, they’re best used fresh and sparingly due to their slightly prickly texture.
- Bees love it, so position near crops that rely on insect pollination.
Further Reading
- Grow Your Own Herbs – RHS Advice
- EasyBuild Polytunnel – Ideal growing space for herbs and companion plants
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