Rock shelter culture
Growing under cover allows extending the harvest seasons of vegetables, fruits, and flowering of flowers. Depending on the budget and available space, the shelter can range from a simple cloche to a heated greenhouse.
Protected cultivation does not necessarily require large technical and financial means. Heating, in particular, is not essential. This makes it accessible to everyone.
Advantages
Advancing planting dates
Many crops can be started earlier in the year, which allows, for example, increasing the number of vegetable harvests, or for flowers to bloom earlier.
Plants that are out of the ordinary
Without even considering profitability, one can use a shelter to sow somewhat rarer, even exotic plants, which require different growing conditions than those available in mainland France. For this, some equipment will be needed, whose common purpose will be to provide plants with higher heat.
Possible solutions
The cloche
Cloche covers (glass, plastic) are used to hasten the growth of the most frost-sensitive plants, whether vegetable or ornamental. They retain the sun's heat and also protect the crops from many "predators".
The cold frame
A simple glazed frame placed on the ground effectively protects fragile crops. Several frames can be heated by a single electric heating cable, simply laid between two layers of 5cm of sand. Seedlings can be started for transplanting as early as December, or even crops grown in place (carrots, turnips,...).
To best stabilize the temperature under the shelter, roll out a straw mat on the glass if cold nights are expected. Conversely, watch for sun rays and ventilate the frames to warm the seedlings.
The tunnel greenhouse
Tunnels reproduce on a large scale the principle of cloches.
Equipped with a galvanized steel structure that is resistant and stainless, it is the market gardening greenhouse par excellence! Although its appearance and insulation do not match those of polycarbonate greenhouses, the tunnel greenhouse offers very good value for money and excellent yields. The tunnel greenhouse is made by covering plastic or metal hoops with good quality plastic (or horticultural polyester). Bright, tunnel greenhouses also offer efficient ventilation systems. Greenhouses with hinged doors are excellent for creating real ventilation tunnels, while greenhouses with side windows continuously ventilate the greenhouse while protecting it from pests.
It allows for tall crops (tomato plants, eggplants, peppers,...).
The glass greenhouse
There are several types of greenhouses made of glass.
Classic glass or horticultural glass greenhouse
One of the most aesthetic greenhouses on the market but not without some drawbacks. Generally, the glass thickness ranges between 3 and 4mm. The thicker the glass, the better insulated the greenhouse. These are expensive greenhouses. While the material is noble and perfectly lets light in, it carries risks unlike polycarbonate or tempered glass. Horticultural glass can break into sharp pieces.
Tempered glass garden greenhouse
Tempered glass greenhouses are 7 times stronger than horticultural glass. In case of impact, tempered glass does not cut as it breaks into small pieces. It is also a very expensive material but has the advantages of horticultural glass without its drawbacks.
The polycarbonate greenhouse
Solid polycarbonate
Very aesthetic, a polycarbonate greenhouse is made of a transparent and unbreakable material. In panel form, it closely imitates glass and can therefore receive maximum sunlight but has poorer insulation than cellular polycarbonate. In temperate or warm regions, this greenhouse is suitable provided ventilation is controlled to avoid overheating.
Its double-pitched roof shape is practical for cleaning and draining the greenhouse roof. Its gutters allow easy rainwater collection.
Cellular polycarbonate
Also called double-wall polycarbonate, it is undoubtedly the most insulating material. Translucent, it captures slightly less heat than transparent polycarbonate but its double wall traps air to make a very good insulator. It is suitable for all types of climates if sunlight is sufficient. At an affordable price, this greenhouse is suitable for frost-sensitive plants, seedling cultivation, or even tall plants thanks to its vertical walls.
Cold, temperate, or warm greenhouse?
What are the differences between a cold greenhouse, a temperate greenhouse, and a warm greenhouse? It is the ability to retain heat that will classify a greenhouse into one category or another. Insulation and the materials composing it thus play an important role.
Cold greenhouse
The temperature of a cold greenhouse varies between 10° and 15°C. Without heating, the temperature can drop below zero depending on the climate. Not suitable for frost-sensitive plants, hardier vegetables and plants thrive there. It can be used to start crops up to 4 weeks in advance.
Temperate greenhouse
The temperature of the temperate greenhouse ranges between 10° and 18°C and does not drop below 5°C thanks to its heating system. It is suitable for sensitive and exotic plants.
Warm greenhouse
Also called tropical greenhouse, the warm greenhouse does not drop below 18°C. Insulated and heated, it is suitable for tropical plants.
What type of crops to grow under greenhouse?
- Tunnel greenhouses are better suited for market gardening of fruits and vegetables thanks to efficient ventilation systems.
- Polycarbonate greenhouses are more insulating, ideal for horticultural cultivation. Frost-sensitive plants and ornamental flowers thrive there thanks to constant temperatures inside the greenhouse. Their vertical walls also allow the cultivation of tall plants such as tomatoes, for example.
- Growing under greenhouse allows good growth of leafy vegetables (lettuces, spinachs…), legumes (beans, peas…), root vegetables (carrots, radish, celery…) and all aromatic herbs.
- Among the crops most comfortable under greenhouse are obviously tomatoes, melons, peppers, eggplants, lettuces, cucumbers, etc.
