Mini greenhouse buying guide

The stand-out feature of mini greenhouses is their size. These structures are so compact that you usually won't be able to fit inside, but they can be used for a wide range of purposes such as:

• seed germination;

• planting;

• overwintering protection for plants or crops.

While there are plenty of options out there, your choice should mainly be driven by:

• what you want to do with the structure:

• the amount of space you have;

• the type of material you need.

Sowing seeds

Seed propagators are really handy for sowing annual vegetable or flower seeds indoors. They can be put to use from February or March which will allow you to put your plants in the ground by May.

These mini greenhouses are basically trays covered with a clear condensation-proof or ventilated cover. The base is nothing more than a seed tray designed to be filled with potting soil. Alternatively, you can use the tray to hold fibre seedling pots. This type of tool is also suitable for plant cuttings.

If you want to grow heat-loving crops like melons, aubergines or tomatoes, go for a heated mini greenhouse. These models are equipped with a heating element or heated mat to keep the soil at a constant temperature.

Planting

Cold frames are designed to be set up outdoors but are lightweight enough to be installed on a balcony. The roof of a cold frame is slanted to allow as much sunlight in as possible.

These structures usually measure about 50 cm to a metre squared and are mainly used to start plants early either through direct sowing or using young shop-bought plants. They can also be used to hold propagators or pots (to transplant young tomato plants, for example).

A cold frame is very handy for growing spring vegetables that don't take up a lot of room such as radishes or lettuces.

The main advantage of a mini greenhouse is that it can be moved around to follow the position of the sun, or set up on a balcony, patio or even indoors.

It's essential to choose the right size of the greenhouse (in terms of surface area and height) whether you have a roomy balcony or just a window sill to play with. While most mini greenhouses come in fairly standard shapes, some may feature shelves to make the most of any vertical space you have.

Mini polytunnels

Mini polytunnels are very practical and easy to move around. Some hard plastic models are modular meaning you can line up the components to create a tunnel that is just the right length for your space. These flexible structures are best for protecting plants or seedlings in a garden.

Upright mini greenhouses

If you're hoping to store your potted plants for winter, an upright mini greenhouse won't take up a lot of floor space. The most basic models are made up of a series of shelves covered by a transparent cover with a zip opening. However, a lean-to greenhouse will also work well.

Flexible plastic: polythylene or PVC

Polythylene and PVC are the cheapest options. They are perfect for very lightweight greenhouses but they do have a limited service life as they will eventually be damaged by UV rays. Go for the thickest plastic possible for more durability.

Polycarbonate

Lightweight, hardwearing and less expensive than glass, polycarbonate offers good thermal insulation and UV protection. Twin wall polycarbonate will block about 99% of UV rays and provide good insulation.

Glass

Greenhouse glass is the most transparent material. It lets in about 90% of sunlight while blocking UV rays. It is, however, very fragile and will break into sharp pieces. Tempered glass, or safety glass, boasts the same light and UV properties as greenhouse glass but is much stronger. Glass is the most expensive option.

Mini greenhouse material comparison

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Greenhouse structure materials 

The structural material of a mini greenhouse is in part dictated by the shape of the structure. PVC and steel are best for round shapes while aluminium and wood are used for straight structures. The structure material of a mini greenhouse is not as important as the outer material. However, it's worth noting that each material offers different properties:

• PVC is sensitive but also lightweight and inexpensive;

• steel is the strongest material but will eventually oxidise (with the exception of stainless steel); 

• aluminium is weather-resistant but more expensive;

• wood will need to be treated over the years.