Growing Basil and Aromatic Herbs: The Complete Guide!

By the AtmoSerre Team

🌿 Introduction

Basil in January, cilantro in November, fresh parsley in the middle of winter… Growing your own herbs all year round is every passionate cook's dream. And this dream is entirely achievable thanks to a polycarbonate garden greenhouse! Contrary to what one might think, herbs are among the easiest and most profitable crops to grow under cover.

In France, we consume an average of 150 to 200 euros worth of fresh herbs per year per household, herbs often grown on the other side of the world, transported by plane, and sprayed with pesticides. Growing your own herbs in a greenhouse is a step towards better health, saving money, and protecting the planet.

In this comprehensive guide, we will show you how to grow basil and all your herbs in a greenhouse productively and sustainably: from varieties to choose, to cultivation techniques, and tips to extend the season and maximize flavors.

🌟 Why Grow Your Herbs in a Greenhouse?

✅ The incomparable advantages of a greenhouse for herbs

📅 Year-round production This is the number one advantage! In open ground, most herbs disappear in autumn and return in spring. In a greenhouse, you maintain continuous production 12 months a year, with fresh basil in December and crisp parsley in January.

🌿 Enhanced aromas Herbs grown under cover develop more concentrated essential oils, and thus more intense aromas. Your greenhouse basil will be incomparably more fragrant than supermarket-bought basil, grown on the other side of the world in industrially gas-heated greenhouses.

💰 Substantial savings A bunch of fresh basil costs between 1.50 and 3€ in the supermarket. A basil plant costs 0.50€ in seeds and can produce for 4 to 6 months in a greenhouse. The annual savings are considerable.

🌡️ Protection of cold-sensitive species Basil dies at the first night below 10°C. Cilantro, Thai basil, lemongrass, and many tropical herbs do not survive the French winter. In a greenhouse, you protect them and grow them all year round.

🏠 An organized and accessible herb garden In a greenhouse, you create a truly organized herb garden, sheltered from rain, accessible in all weather. No more going out in the rain to pick thyme!

Discover our "L'Intemporelle" polycarbonate greenhouse to create your aromatic paradise under cover.

🌿 Ideal Herbs for the Greenhouse

Not all herbs behave the same way in a greenhouse. Here is an overview of the best species to grow under cover, classified by level of requirement.

🟢 Easy Herbs (ideal for beginners)

🌿 Basil (Ocimum basilicum) The king of greenhouse herbs! Basil loves heat and light, two conditions perfectly met in a greenhouse. It produces abundantly from May to November (and all year round if the greenhouse is heated). There are dozens of varieties: sweet basil (the classic), Neapolitan basil (large leaves), purple basil, Thai basil, lemon basil...

🌿 Parsley (Petroselinum crispum) Very easy to grow in a greenhouse, parsley is cold-hardy and can be grown almost all year round under cover. Flat-leaf varieties are more aromatic than curly varieties. In a greenhouse, flat-leaf parsley can reach an impressive size.

🌿 Chives (Allium schoenoprasum) Perennial and very hardy, chives are easily grown in pots in a greenhouse. They regrow indefinitely after each cut and can be divided every 2-3 years to multiply plants.

🌿 Mint (Mentha sp.) Beware, mint is very invasive! Always grow it in a pot to prevent it from colonizing the entire greenhouse. There are dozens of varieties: peppermint, Moroccan mint (for tea), chocolate mint, apple mint... In a greenhouse, it produces all year round.

🟡 Mediterranean Herbs (a little more demanding)

🌿 Thyme (Thymus vulgaris) Thyme is a Mediterranean plant that appreciates the warmth and sun of the greenhouse. It needs well-drained soil (add sand to your substrate) and low humidity. It does not tolerate excessive watering.

🌿 Rosemary (Rosmarinus officinalis) Can become a true shrub in a greenhouse! Rosemary grows slowly but becomes very productive after 2-3 years. It needs a lot of sun and a very well-draining substrate. It tolerates cold winters in unheated greenhouses.

🌿 Sage (Salvia officinalis) A very productive medicinal and culinary herb in a greenhouse. Sage tolerates drought well and prefers a slightly calcareous substrate. It can become a beautiful bush in a greenhouse after 2-3 years.

🌿 Tarragon (Artemisia dracunculus) French tarragon (the real one, not Russian) is essential in any self-respecting French kitchen. In a greenhouse, it produces tender and very aromatic shoots for 8 to 9 months of the year.

🔴 Exotic Herbs (for the more adventurous)

🌿 Cilantro (Coriandrum sativum) Difficult to grow in open ground in summer (it quickly bolts in hot weather), cilantro performs better in a greenhouse where the temperature can be better regulated. Sow in small quantities every 3-4 weeks for continuous production.

🌿 Thai Basil (Ocimum basilicum var. thyrsiflora) With anise-like and slightly peppery flavors, Thai basil is essential in Asian cuisine. It is grown exactly like common basil but grows faster and longer.

🌿 Lemongrass (Cymbopogon citratus) This large tropical grass can reach 1.5 m in a greenhouse! It needs a lot of heat and humidity. In an unheated greenhouse, bring it indoors in winter or protect it well.

🌿 Stevia (Stevia rebaudiana) The "natural sugar"! Stevia is 200 times sweeter than sugar with no calories. It is grown in a greenhouse like a geranium and will provide you with sweet leaves to naturally sweeten your drinks and desserts.

📊 Seasonal Summary

🏡 Preparing Your Greenhouse for Herbs

📐 Space organization

Herbs are compact plants that adapt very well to small spaces. In a 6 to 9 m² greenhouse, you can easily grow 15 to 20 different species of herbs while leaving room for other vegetables.

Organization tips:

• Group herbs by watering needs: on one side, Mediterranean herbs (thyme, rosemary, sage) that like dry conditions, on the other, herbs that like humidity (basil, cilantro, parsley).
• Use greenhouse shelves to create multiple growing levels and maximize vertical space.
• Place taller herbs (rosemary, lemongrass) on the north side to avoid shading others.

🪴 Suitable containers

Herbs adapt to many containers:

• Individual pots: ideal for mint (to keep isolated) and rosette species like parsley.
• Long planters: perfect for small herbs like chives, basil, or tarragon.
• Wooden raised garden beds: aesthetic and functional, they regulate humidity better than plastic pots.
• Hanging baskets: for trailing herbs like creeping thyme or mint.

🌱 The ideal substrate

Herbs generally prefer a light, well-draining, and not too rich substrate:

• 50% all-purpose potting mix
• 30% mature compost
• 20% sand or perlite

For Mediterranean herbs (thyme, rosemary, sage), add another 10% gravel or pumice to ensure perfect drainage. These plants hate having wet feet.

🌱 Sowing and Planting

🌿 Start from seeds or plants?

Seeds: cheaper and allow access to rare varieties not available as plants. Germination usually takes 1 to 3 weeks depending on the species. Ideal for: basil, parsley, cilantro, dill.

Plants: faster, allowing immediate production. Ideal for: thyme, rosemary, sage, mint (almost always available in garden centers).

Division: some perennial herbs (mint, chives, tarragon) can be divided from existing plants. Simply separate the clumps and replant them.

📅 Greenhouse sowing calendar

🌱 Basil Sowing Technique (most popular)

Basil is the star of aromatic herbs in the greenhouse. Here's how to successfully sow it:

1. Sow in trays or pots in February-March in the greenhouse
2. Place 3-4 seeds per pot, 0.5 cm deep
3. Water gently with a sprayer
4. Cover with plastic film, basil germination requires 22-25°C
5. Germination occurs in 7 to 14 days
6. Thin to 1-2 plants per pot when they have 2 true leaves
7. Transplant into a final container or pot when plants are 6-8 cm tall

💡 Basil tip: Sow basil every 4-6 weeks to always have productive young plants. A basil plant at the end of its cycle (when it goes to seed) becomes less aromatic; it's better to replace it.

💧 Care and Watering

💧 Watering according to species

The most common mistake with aromatic herbs is overwatering. Most Mediterranean herbs (thyme, rosemary, sage, oregano) tolerate and even appreciate a slight dryness between waterings.

Herbs that love humidity (water 2-3 times/week):

• Basil, parsley, coriander, chives, mint, tarragon

Herbs that prefer dry conditions (water once/week):

• Thyme, rosemary, sage, oregano, lavender

Universal rule: Always wait until the first inch of substrate is dry before watering. Insert your finger into the soil; if it's damp deep down, don't water yet.

✂️ Harvesting and Pruning

Contrary to what one might think, regularly trimming your herbs promotes their growth and production! The more you pick, the more they produce.

Basil harvesting technique:

• Always cut above a pair of leaves
• Never remove more than a third of the plant at once
• Remove flowers as soon as they appear to prolong leaf production (when basil flowers, it becomes less aromatic and weakens)

Thyme and rosemary harvesting technique:

• Cut stems 5 to 10 cm long, never taking old wood
• Regular pruning after flowering keeps plants compact and productive

🌡️ Temperature Management and Ventilation

Aromatic herbs need good ventilation to prevent fungal diseases. An automatic window opener system is ideal for maintaining good air circulation without constantly monitoring your greenhouse.

📅 The Aromatic Herb Calendar in the Greenhouse

❄️ Winter (December - February)

• Plant: parsley, chives, mint, thyme, rosemary (all cold-hardy)
• Maintain: a minimum temperature of 5-8°C (most herbs survive light frost)
• Harvest: parsley, chives, thyme, rosemary, sage
• Avoid: sowing basil (needs warmth)
• Tip: a P40 winter fleece placed directly on the plants can provide an additional 3-4°C

🌸 Spring (March - May)

The most dynamic season for aromatic herbs in the greenhouse!

• Sow: basil (under warm cover), parsley, coriander, dill, chives
• Plant: thyme, rosemary, sage, tarragon
• Harvest: parsley, chives, thyme, rosemary, sage
• Action: divide your clumps of chives and mint to multiply plants

☀️ Summer (June - August)

• Sow: coriander (quick rotation), basil (renewal), dill
• Harvest: all herbs at their peak production!
• Caution: ventilate abundantly; basil suffers above 35°C
• Install: a shade net to protect herbs most sensitive to intense heat

🍂 Autumn (September - November)

• Sow: parsley, coriander for winter production
• Harvest: still all herbs in large quantities
• Prepare: bring fragile herbs (lemongrass, Thai basil) into the greenhouse
• Store: dry or freeze excess herbs

🐛 Diseases and Pests

🦠 Main diseases of aromatic herbs in the greenhouse

Botrytis (gray mold) Gray fuzz on stems and leaves, favored by humidity and lack of ventilation. Very common on basil in greenhouses. Prevention: good ventilation, sufficient spacing, watering at the base.

Powdery mildew White fuzz on leaves, common on basil, mint, and sage in warm weather. Organic treatment: baking soda (1 tbsp/liter of water), milk diluted to 1/9.

Damping-off Young seedlings collapse at the collar. Caused by a fungus (Pythium) favored by excess moisture. Prevention: well-draining substrate, moderate watering, good aeration.

🐛 Common Pests

Aphids Very common on basil, mint, and parsley. Multiply rapidly in greenhouses. Treatment: diluted black soap (5-10 ml/liter), nettle manure, ladybug release.

Whiteflies Under leaves, cause general weakening. Treatment: yellow sticky traps, insecticidal soap.

Slugs and snails Less common in greenhouses but can get in. They love parsley and basil. Prevention: copper tape around trays, iron phosphate granules (organic-approved).

For a comprehensive crop protection strategy, consult our guide on How to protect your plants from diseases in a greenhouse.

🌿 Harvesting and Storage

🌿 How to harvest your aromatic herbs well

The golden rule: always harvest in the morning, after the dew has evaporated but before the midday heat. This is when essential oils are most concentrated and aromas are most intense.

Basil: pick leaves or stems one by one. Systematically remove flower stalks to prolong production.

Parsley: cut entire stems at the base, taking the outer ones first to allow the center to develop.

Thyme and rosemary: cut stems 5 to 10 cm long with clean scissors.

Mint: cut above a node to encourage branching.

📦 Storing fresh herbs

In the refrigerator: fresh herbs can be stored for 5 to 10 days by wrapping them in slightly damp absorbent paper.

In water: like a bouquet of flowers! Place the stems in a glass of water in the refrigerator. Parsley, coriander, and basil (at room temperature for the latter) can be stored this way for 1 to 2 weeks.

Freezing: chop your herbs, fill ice cube trays, and cover with water or olive oil. Freeze directly and unmold into cubes for easy use all year round. Works very well for: parsley, chives, basil, coriander.

Drying: tie small bouquets and hang them upside down in a dry, airy place. Ideal for: thyme, rosemary, sage, bay leaf, lavender. Dried herbs can be stored for 6 to 12 months in airtight jars.

Infusion in oil: infuse your fresh herbs in olive oil for 2-4 weeks in the sun (in a greenhouse, it's ideal!). You'll get a delicious aromatic oil for cooking and salads.

❓ FAQ - Your Questions about Aromatic Herbs in the Greenhouse

🌿 Can basil be grown in a greenhouse in winter without heating? It's difficult but not impossible. Basil tolerates temperatures below 10°C poorly and stops growing below 15°C. Without heating, it will survive in the greenhouse but will be unproductive in winter in most French regions. For winter basil production, a small auxiliary heater maintaining the greenhouse at a minimum of 15-18°C is necessary. However, parsley, chives, and Mediterranean herbs (thyme, rosemary) resist winter perfectly in an unheated greenhouse.

💧 How often should basil be watered in a greenhouse? Basil likes moist but never soggy substrate. In summer, water every 1 to 2 days. Check by inserting your finger into the soil; the first inch should be dry before watering again. Basil is very sensitive to excess water (damping-off, root rot) but also suffers from lack of water (falling leaves, bitter taste). Balance is key.

🌱 How many aromatic herb plants for a family? For a family of 4 people who cook regularly, plan for: 3-4 basil plants (renewed regularly), 2 flat-leaf parsley plants, 1 chive clump, 1 thyme plant, 1 rosemary plant, 1 sage plant, and 2 mint plants (in separate pots). Add according to your taste: coriander, tarragon, dill...

🔄 Can thyme and rosemary stay in the greenhouse all year round? Yes, thyme and rosemary are perennial Mediterranean plants that adapt very well to greenhouse life all year round. However, be careful: these plants need a relative winter dormancy (reduced watering, cooler temperatures) to remain productive in the long term. Do not keep your greenhouse too hot in winter for these species.

🌿 How to prevent my basil from going to seed too quickly? Basil bolting (going to seed) is accelerated by heat stress, lack of water, and long days. To delay this phenomenon: remove flowers as soon as they appear, maintain regular watering, ventilate the greenhouse to avoid heat stress, and sow new plants regularly to always have young and productive specimens. To learn more about managing your greenhouse and its ventilation throughout the seasons, consult our article on "Greenhouse Ventilation: Advantages and Mistakes to Avoid."

🪴 Can AtmoSerre grow beds be used for herbs? Absolutely! Our wooden grow beds and galvanized steel beds are perfectly suited for growing herbs. Wood naturally regulates humidity (it absorbs excess water and gradually releases it), which is ideal for herbs. Just ensure good drainage at the bottom of the bed (a 3-5 cm layer of gravel).

🎯 Conclusion

Growing your own herbs in a greenhouse is one of the simplest, fastest, and most rewarding experiences in sheltered gardening. In just a few weeks, you'll have fresh basil, crisp parsley, and fragrant cilantro at your fingertips, no matter the outdoor conditions.

A polycarbonate greenhouse creates an ideal microclimate for the vast majority of herbs: controlled warmth, protection from bad weather, and evenly diffused light. Combined with carefully selected grow beds and a suitable watering system, it becomes a truly productive herb garden all year round.

Get started! Begin with a few simple species (basil, parsley, chives, mint) and gradually expand your collection. Discover our range of AtmoSerre polycarbonate greenhouses now and transform your passion for plants into a sustainable and flavorful herb production. 🌿

Sources: INRAE, Société Nationale d'Horticulture de France (SNHF), Institut des Plantes à Parfum, Médicinales et Aromatiques (ITEIPMAI)