DIY tunnel greenhouse for your cannabis plants

In some climates, summer sets in late and/or autumn comes early with lots of wind and rain. The cannabis plants have a hard time maturing and developing their full potential under these conditions. Maybe that's why you've thought about building a greenhouse yourself. This can solve some of the growing problems of outdoor growing and significantly extend the growing period. Growing in a greenhouse is an effective way to grow high quality and high yielding cannabis. In mild climates, you can even grow in a greenhouse all year round.

Before you get started, there are a few things to consider:

Choose the right cannabis strain

Choosing the right cannabis strain is an important part of any cultivation. Decide whether you want to grow a cannabis strain with a lot of CBD or a lot of THC, whether it should be an autoflowering strain, an indica dominant or sativa dominant strain. The expected growth height of a strain as well as the resistance to fungal diseases and pests also play an important role. Some cannabis strains can grow amazingly tall outdoors and quickly outgrow you. Huge plants will of course produce huge yields, but if you decide to grow a monster plant, you should plan for the necessary space in advance and design the greenhouse accordingly. For example, a growing area of 3 x 3 m and a height of 3 m may well be too small if you want to grow the really big plants. However, if you keep the cannabis plants in a medium size and choose appropriate strains or autoflowering strains, a smaller greenhouse is quite sufficient.
The plants should not be planted too close to the foil of the greenhouse, so that sufficient ventilation is ensured and there is no moisture build-up. This could cause the spread of harmful fungi. Consider this additional space needed and include it in the calculation.
Even if it sounds premature, think about where you can dry the (abundant) yields later. The greenhouse itself is not suitable for this.

Building a tunnel greenhouse

Tunnel greenhouses are inexpensive, easy to assemble and very effective. A series of tubes are bent into arches and placed at a set distance to form semicircles and attached to a frame of base boards for stability. Plastic sheeting is then placed over the bent tubes to protect the inside from the weather while still letting in sunlight. You can build tunnel greenhouses yourself or buy them ready-made with all the necessary components.

Tunnel greenhouses for cannabis plants can be built in different sizes and designs.

What you should look out for in a foil tunnel:

For hobby gardeners who only have limited space available, a tunnel greenhouse can be just the right thing and a good alternative to fixed greenhouses. Choose the right film for the tunnel greenhouse: UV-impermeable PE film is suitable, as it is more durable than non-UV-resistant film and does not start to crumble after a short time. Special garden films that are UV-resistant are more expensive, but last much longer (several years).
Good ventilation plays an important role in every greenhouse. Condensation forms easily and quickly here. Design the tunnel greenhouse so that you can open the sides and the front without any problems.

1. Foil tunnels can be made from iron pipes, plastic pipes, bamboo or even fibreglass rods. Before building the tunnel, you should loosen the soil on which you want to place it and remove weeds. Then add humus and compost.
2. Then stick the tubes or sticks into the ground at even intervals of 50 cm, approx. 20 cm deep. The round arches are then fastened with string and, if necessary, with a wooden strip.

Or like this: Attach pipes to the floor

The tubes can be additionally stabilised with vertical slats or rods. Then the foil is pulled tightly over the scaffolding and fastened well to the ground with stones and pegs. For ventilation, one side can simply be pushed up.

A special garden fleece as a substrate prevents weeds and unwanted plants from spreading.

If you want to build an effective greenhouse, it's not just about putting up a structure. It is also important to create a healthy ecosystem. To do this, you need to ensure that there is good and sufficient ventilation and that temperatures and humidity do not get too high. Open the sides of the tunnel greenhouse when the sun is shining and the temperatures are high. To prevent mildew and other fungal diseases, constant air movement is crucial. You can further improve air circulation by installing a fan.

Use a hygrothermometer to keep track of the temperature in the greenhouse and the humidity. Ideally, the temperature should be between 20° and 25° degrees. Especially flowering plants should be in an environment with a humidity that is not too high (40%-50%).