How to Grow Garlic in a Greenhouse

How to Grow Your Own Garlic in a Greenhouse

Growing garlic in a greenhouse is a rewarding experience that can yield a bountiful harvest of this flavourful and versatile vegetable. Whether you're a seasoned gardener or just starting out, greenhouse garlic cultivation offers numerous advantages over traditional outdoor growing methods. In this guide, we'll explore the ins and outs of indoor garlic growing, from choosing the right varieties to harvesting and storing your crop.

Benefits of Growing Garlic in a Greenhouse

Extending the Growing Season

One of the primary advantages of greenhouse garlic cultivation is the ability to extend your growing season. In a greenhouse, you can start planting garlic earlier in the autumn and continue harvesting later into the spring. This extended season allows for multiple plantings and a more consistent supply of fresh garlic throughout the year. Additionally, the controlled environment of a greenhouse protects your garlic from unexpected frosts or harsh weather conditions that might damage outdoor crops.

Protection from Pests and Diseases

Greenhouse garlic growing provides a significant level of protection from common pests and diseases that often plague outdoor gardens. The enclosed space acts as a barrier against many insects and small animals that might otherwise feast on your garlic plants. Moreover, the controlled environment makes it easier to manage humidity levels and air circulation, reducing the risk of fungal diseases that can be problematic for garlic. This protection often results in healthier plants and higher yields compared to outdoor cultivation.

Choosing the Right Garlic Varieties

Hard neck vs. Soft neck Garlic

When it comes to selecting garlic varieties for your greenhouse, it's important to understand the difference between hard neck and soft neck types. Hard neck garlic typically produces fewer, larger cloves and is known for its complex flavours. It also develops a flowering stem called a scape, which can be harvested and used in cooking. Soft neck garlic, on the other hand, produces more cloves per bulb and is generally easier to braid for storage. Both types can be successfully grown in a greenhouse, but hard neck varieties often benefit more from the controlled climate, as they require a period of cold to develop properly.

Here's a chart showing some popular garlic varieties suitable for UK greenhouses:

Variety	When to Sow	When to Plant Out	When to Harvest
Early Purple Wight	September-November	October-November	May-June
Solent Wight	October-November	November-December	June-July
Germidour	October-December	November-January	June-July
Elephant Garlic	September-November	October-December	July-August
Chesnok Red	October-November	November-December	July-August

Preparing Your Greenhouse for Garlic Cultivation

Soil Preparation and Drainage

Proper soil preparation is crucial for successful greenhouse garlic cultivation. Garlic thrives in well-draining, fertile soil rich in organic matter. Before planting, work plenty of compost or well-rotted manure into your greenhouse beds or containers. This not only improves soil structure but also provides essential nutrients for your garlic plants. Ensure that your growing area has excellent drainage, as garlic doesn't tolerate waterlogged conditions. If you're using raised beds or containers in your greenhouse, this becomes even more important. Consider adding some coarse sand or perlite to your soil mix to improve drainage if needed.

Temperature and Humidity Control

Maintaining the right temperature and humidity levels is key to successful greenhouse garlic growing. Garlic prefers cool temperatures during its initial growth stages, ideally between 0°C and 10°C (32°F to 50°F). As the plants mature, they can tolerate warmer temperatures, but it's important to avoid excessive heat, which can stress the plants and reduce bulb size. Proper ventilation is crucial in regulating both temperature and humidity. Use vents, fans, or even a cold frame within your greenhouse to maintain optimal conditions. Aim for a humidity level around 60-70% to prevent fungal issues while providing enough moisture for healthy growth.

Planting Garlic in a Greenhouse

Planting Techniques for Greenhouse Garlic

When it comes to planting garlic in your greenhouse, timing and technique are everything. The best time for winter garlic planting is typically between September and November, allowing the cloves to establish roots before the coldest part of winter. Break apart the garlic bulbs into individual cloves just before planting, keeping the papery skin intact. Plant each clove about 5-10 cm (2-4 inches) deep, with the pointed end facing upwards. Space the cloves about 10-15 cm (4-6 inches) apart in rows, with 30 cm (12 inches) between rows. This spacing allows for good air circulation and gives the bulbs room to develop. After planting, water thoroughly and add a layer of mulch to help retain moisture and suppress weeds.

Caring for Greenhouse Garlic

Watering and Fertilizing Garlic Plants

Proper watering and fertilization are crucial for healthy greenhouse garlic cultivation. Garlic prefers consistent moisture but can't tolerate waterlogged soil. Water deeply but infrequently, allowing the top inch of soil to dry out between waterings. This encourages deeper root growth and helps prevent fungal diseases. In terms of fertilization, garlic is a heavy feeder. Start with a balanced, organic fertilizer at planting time. As the plants grow, switch to a high-nitrogen fertilizer in early spring to promote leaf growth. Once the bulbs begin to form, usually around May, switch to a fertilizer higher in phosphorus and potassium to encourage bulb development. Always water after fertilizing to help distribute nutrients evenly.

Pruning and Training Garlic in a Greenhouse

While garlic doesn't require extensive pruning, there are a few key practices that can improve your harvest. For hardneck varieties, remove the scapes (flower stalks) when they appear in late spring or early summer. This redirects the plant's energy into bulb formation rather than flower production. You can eat these scapes - they're delicious in stir-fries or pesto. As for training, garlic generally grows upright on its own, but you may need to provide some support if plants become top-heavy. Simple bamboo stakes or twine can be used to keep plants upright if needed. Regular removal of any yellowing or diseased leaves will help maintain plant health and improve air circulation.

Common Problems and Solutions

Pest Management in Greenhouse Garlic

While growing garlic in a greenhouse provides some protection from pests, it's not entirely immune. Common pests that can affect greenhouse garlic include thrips, onion flies, and nematodes. Regular inspection of your plants is key to early detection and management. For organic pest control, consider introducing beneficial insects like ladybirds or lacewings. Neem oil can be effective against many common pests. If you notice any plants with severe pest damage, it's best to remove them promptly to prevent the problem from spreading. Maintaining good hygiene in your greenhouse, such as removing plant debris and weeds, can also help reduce pest issues.

Harvesting and Storing Greenhouse Garlic

When and How to Harvest Greenhouse Garlic

Knowing when and how to harvest your greenhouse garlic is crucial for getting the best flavour and storage life. Generally, garlic is ready to harvest when the lower leaves start to yellow and die back, usually in early to midsummer. To check if your garlic is ready, carefully dig up a bulb and inspect it. The cloves should be well-formed and the outer skin papery. To harvest, gently loosen the soil around the bulbs with a garden fork and carefully lift them out. Avoid pulling them straight out of the ground as this can damage the stems. Once harvested, brush off excess soil but don't wash the bulbs. Tie the plants in bundles of 5-10 and hang them in a well-ventilated, shady spot to cure.

Curing and Storing Your Garlic Crop

Proper curing and storage are essential for preserving your garlic harvest. After harvesting, allow your garlic to cure for 2-3 weeks in a dry, well-ventilated area out of direct sunlight. This process helps dry out the outer layers of the bulb, improving storage life. Once cured, trim the roots and cut the stems about 2.5 cm (1 inch) above the bulb. For long-term storage, keep your garlic in a cool, dry place with good air circulation. A mesh bag or open basket works well. Avoid storing garlic in the refrigerator, as the cold and humidity can cause sprouting. Properly stored garlic can last for several months, allowing you to enjoy your homegrown harvest well into the winter.

Growing garlic in a greenhouse offers many advantages, from extended growing seasons to protection from pests and harsh weather. With the right techniques and care, you can enjoy a bountiful harvest of this flavourful and versatile vegetable. Whether you're using a traditional greenhouse or an aluminium greenhouse, these tips will help you successfully cultivate garlic year-round. Happy growing!

FAQ

Can garlic be grown in greenhouses?

Yes, garlic can be successfully grown in greenhouses. Greenhouse garlic cultivation offers several advantages, including protection from extreme weather and pests, and the ability to control growing conditions more precisely.

What is the best month to plant garlic?

The best time to plant garlic in a greenhouse is typically between September and November. This allows the cloves to establish roots before winter and ensures a good harvest the following summer.

Can I plant supermarket garlic?

While it's possible to plant supermarket garlic, it's not recommended. Supermarket garlic may be treated with growth inhibitors and might not be suited to UK growing conditions. It's better to use garlic bulbs specifically sold for planting, which are disease-free and adapted to local conditions.

Can you grow garlic outside in the UK?

Yes, garlic can be grown outside in the UK. However, growing garlic in a greenhouse offers more control over growing conditions and can result in a better harvest, especially in areas with harsh winters or wet springs.

If you're interested in growing other crops in your greenhouse, why not try growing strawberries in a greenhouse? Or for more ideas on what to grow, check out our beginner's guide to greenhouse growing. Remember, growing fruit at home can be a rewarding experience, whether it's garlic, strawberries, or other delicious crops.

If you liked this article and have any feedback or questions, please reach out to us at [email protected]