How to Grow Herbs in your Greenhouse

Growing Herbs in Your Greenhouse: A Complete Guide

Growing herbs in a greenhouse is a fantastic way to enjoy fresh flavours all year round. Whether you're a seasoned gardener or just starting out, this guide will help you make the most of your greenhouse for herb cultivation. I've been growing herbs in my greenhouse for years, and I'm excited to share my tips and tricks with you. Let's dig in and explore the wonderful world of greenhouse herbs together!

Greenhouse gardening offers unique advantages for herb enthusiasts. With the right setup, you can create an ideal environment for your plants, extending the growing season and protecting them from harsh weather. From basil to thyme, a wide variety of herbs can thrive in this controlled setting.

In this article, we'll explore the benefits of greenhouse herb growing, the best varieties to cultivate, and essential tips for success. We'll also cover sowing, propagation, and overwintering techniques to keep your herb garden thriving throughout the year. So, let's roll up our sleeves and get started on your greenhouse herb adventure!

Benefits of Growing Herbs in a Greenhouse

Year-Round Herb Production

One of the biggest perks of growing herbs in a greenhouse is the ability to harvest fresh herbs throughout the year. The controlled environment allows you to maintain ideal growing conditions, even when the weather outside is less than favourable. This means you can enjoy fresh basil in your winter soups or add a sprig of rosemary to your roast any time you fancy. I remember the first time I plucked fresh mint from my greenhouse in December - it felt like magic!

Protection from UK Weather

Let's face it, British weather can be a bit unpredictable. A greenhouse acts as a shield, protecting your delicate herbs from sudden downpours, frost, and strong winds. This protection is especially crucial for tender herbs like basil and coriander, which can quickly suffer in cold or wet conditions. I've seen my outdoor herbs struggle through a wet summer, while their greenhouse counterparts thrived. It's like giving your herbs a cosy jumper to wear all year round!

Pest Control for Healthier Herbs

Greenhouses provide a natural barrier against many common garden pests. This means fewer nibbled leaves and healthier plants overall. While some pests can still find their way in, it's much easier to spot and deal with issues in a contained environment. I've found that my greenhouse herbs are much less likely to fall victim to slugs and snails, which is a huge relief!

Best Herbs to Grow in a UK Greenhouse

Here's a table of the top 10 herbs that thrive in UK greenhouses:

Herb	When to Sow	When to Harvest	Used for Cooking
Basil	March-May	June-September	Italian dishes, pesto
Chives	March-April	May-September	Salads, soups, garnish
Coriander	March-August	May-September	Asian and Mexican cuisine
Dill	April-July	June-September	Fish dishes, pickles
Parsley	March-August	May-October	Garnish, sauces, soups
Oregano	March-May	July-October	Italian and Greek dishes
Rosemary	March-May	Year-round	Roasts, Mediterranean dishes
Sage	March-May	June-October	Poultry dishes, stuffing
Thyme	March-May	June-October	Soups, stews, meat dishes
Mint	March-May	April-September	Teas, desserts, cocktails

Essential Tips for Greenhouse Herb Growing

Proper Watering Techniques

Watering is crucial for healthy herb growth, but it's easy to overdo it in a greenhouse. Always check the soil moisture before watering. Most herbs prefer well-draining soil that's allowed to dry slightly between waterings. I water at the base of the plants to avoid wetting the leaves, which can lead to fungal issues. Remember, it's better to underwater than overwater - herbs are generally quite forgiving if you forget to water for a day or two.

Pruning and Pinching for Bushy Growth

Regular pruning encourages bushier, more productive herb plants. I pinch off the growing tips of herbs like basil and mint to promote branching. For woody herbs like rosemary and thyme, I trim back about one-third of the growth after flowering to keep them compact and healthy. Don't be afraid to be a bit ruthless - most herbs respond well to a good haircut!

Ventilation and Temperature Control

Proper airflow is essential in a greenhouse to prevent fungal diseases and regulate temperature. I open vents or doors on warm days to allow fresh air circulation. In summer, you might need to provide shade to prevent overheating. During colder months, consider using a small heater to maintain a minimum temperature for tender herbs. A mini greenhouse can be easier to manage in terms of temperature control.

Sowing and Propagating Herbs in Your Greenhouse

Starting Herbs from Seeds

Starting herbs from seeds is cost-effective and rewarding. I use seed trays filled with a good quality, peat-free compost. Most herb seeds are small, so I sow them thinly on the surface and cover lightly with vermiculite. Keep the soil moist but not waterlogged, and you'll see seedlings emerge in 1-3 weeks for most varieties. It's a bit like magic watching those first tiny leaves pop up!

Propagating Herbs from Cuttings

Many herbs can be propagated from cuttings, which is a great way to multiply your plants. I take 10-15cm cuttings from non-flowering stems, remove the lower leaves, and place them in a pot of well-draining compost. Keep them moist and in a warm, bright spot, but out of direct sunlight until roots develop. It's a fantastic way to get free plants and share with friends!

Overwintering Herbs in a UK Greenhouse

Protecting Tender Herbs from Frost

While a greenhouse offers good protection, extra measures may be needed during harsh winters. I use horticultural fleece to cover tender herbs on particularly cold nights. Grouping pots together can also help create a microclimate that's a bit warmer. For very tender herbs, consider bringing them into the house or using a heated propagator. You can also grow in an aluminium greenhouse for better insulation.

Preparing Perennial Herbs for Spring

As winter ends, it's time to prepare your perennial herbs for the new growing season. I prune away any dead or damaged growth and refresh the compost in pots. Gradually increase watering as daylight hours lengthen and temperatures rise. This is also a good time to divide and repot overgrown herbs to encourage fresh growth. It's like giving your herbs a spring clean!

Common Problems and Solutions for Greenhouse Herbs

Even in a greenhouse, herbs can face challenges. Overwatering is a common issue, leading to root rot. Ensure pots have good drainage and only water when the top inch of soil feels dry. Pest problems can still occur - keep an eye out for aphids and whitefly, which can be controlled with organic sprays or natural predators like ladybirds.

Fungal diseases can be problematic in the humid greenhouse environment. Prevent these by maintaining good air circulation and avoiding overhead watering. If you notice powdery mildew or other fungal issues, remove affected parts promptly and consider using an organic fungicide.

Nutrient deficiencies can show up as yellowing leaves or stunted growth. Use a balanced, organic fertiliser formulated for herbs every few weeks during the growing season. Remember, most herbs prefer lean soil, so don't overdo it with the feed.

Harvesting and Using Your Greenhouse-Grown Herbs

Harvesting herbs regularly encourages bushier growth and prevents flowering, which can alter the flavour. For most leafy herbs, I snip off the top few inches, just above a leaf joint. This encourages the plant to branch out. For woody herbs like rosemary, cut stems back by about one-third.

To preserve your harvest, you have several options. Air-drying works well for herbs like oregano and thyme - simply hang small bunches in a warm, dry place. Alternatively, freeze herbs in ice cube trays with a bit of water or oil for easy use in cooking. Fresh herbs can be kept in the fridge, wrapped in slightly damp kitchen paper and stored in a plastic bag.

Experiment with your fresh herbs in cooking. Try making herb-infused oils or vinegars, or create your own herb salt by blending dried herbs with sea salt. The possibilities are endless when you have a constant supply of fresh herbs at your fingertips! You can even grow using a raised bed in your greenhouse for a more abundant harvest.

FAQ

Which herbs grow well in a greenhouse?

Many herbs thrive in greenhouse conditions. Some of the best options include basil, coriander, parsley, chives, oregano, thyme, rosemary, and sage. These herbs benefit from the controlled environment and extended growing season that a greenhouse provides. For beginners, check out our What to grow in a Greenhouse Beginners Guide.

Can you grow herbs in a greenhouse all year?

Yes, with proper care and temperature control, you can grow herbs in a greenhouse throughout the year. Some hardy perennials like rosemary and thyme will continue growing even in cooler months. For more tender herbs like basil, you may need to provide additional heat during winter. A cold frame can be useful for hardening off plants before moving them outdoors.

How often should you water herbs in a greenhouse?

The watering frequency for greenhouse herbs depends on various factors including the type of herb, pot size, and current weather conditions. Generally, water when the top inch of soil feels dry. Most herbs prefer well-draining soil and don't like to be waterlogged. Always check the soil moisture before watering to avoid overwatering.

What herbs cannot be planted next to each other?

While most herbs are good companions, there are a few that don't play well together. Fennel is known to inhibit the growth of many other herbs and should be planted separately. Mint is also best kept in its own pot as it can quickly overtake other plants. Basil and rue are also said to have a negative effect on each other when planted close together.

Growing herbs in a greenhouse opens up a world of culinary possibilities. With the right care and attention, you can enjoy a year-round supply of fresh, flavourful herbs right at your fingertips. Happy herb growing!

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