Gardening under Glass

Gardening under glass allows the gardener to maximise growing space in the garden and to extend the growing season. Greenhouses, cloches and cold-frames are all useful additions to the garden and can increase the variety of things you grow. The following will take a look at the structures you can choose.

Greenhouses

The greenhouse is the most easily recognised growing structure. It is the perfect all-weather place to cultivate plants, allowing you to extend the range of plants you grow. It will also provide the right conditions to propagate and overwinter less hardy plants or grow tender ones.

Greenhouses minimise the damage caused by low temperatures and penetrating winds and heated greenhouses will protect against frosts. They are especially useful to grow half-hardy annuals and vegetables.

There are many different styles of structure to choose. Greenhouses are either built from wood, metal or PVC. Wooden structures are more aesthetically pleasing than metal and is also slightly warmer, easier to repair and better for fitting shelves. However, it is heavy to work with when building and will need staining or painting, which can be time consuming and costly. Steel and aluminium ones are light and easy to handle and can take larger panes of glass than wooden constructions and therefore let in more light to plants.

Greenhouses also come with the option of using glass or plastic panes. Glass maintains a more stable environment than plastic and also retains heat better. Plastic is less attractive than glass, will lose transparency over time and can become brittle. Condensation is also more problematic in plastic greenhouses - water droplets on plastic and not transparent and this an reduce light entry to the structure and also encourage mould and mildew. However, plastic is cheaper to repair than glass - glass obviously breaks more easily than plastic and it can be costly and time consuming to install new panes. Plastic also has the benefit of being lighter and easier to handle than glass.

When siting a greenhouse one needs to ensure that the maximum light will enter. Avoid placing near overhanging trees as this will create too many shadows. Avoid windy and exposed sites and ensure that you have good access to and from the greenhouse.

Greenhouses can become very warm during the summer months so ventilation is important. It may also be necessary to invest in shading blinds or paint to prevent scorching.

Cold Frames

Cold frames are low level structures that are best used to raise and harden off plants. They can be heated, however, with electric warming cables, so can be used to raise tender plants. They are best sited so that they do not get too much direct sunshine.

The traditional style of cold frame has brick sides with glass lights. The lights can, however, be heavy and cumbersome to move around. Modern frames are more portable and are made of wood, plastic or aluminium.

Cloches

Cloches come in a variety of shapes and sizes. They can be used to cover single plants or cover larger groupings of plants. Glass cloches are the most expensive but are the most durable. They also give the best light transmission, but are heavy to handle and can break. Plastic cloches consist of double layered corrugated propylene, which provides good growing conditions.

Cloches need to be anchored down to prevent them blowing away. Open ended cloches can be a problem in windy conditions as the wind can tunnel down and damage plants - therefore, close off the ends with a pane of glass or plastic.

As with all growing structures, ventilation is vital in warm and humid weather. Tilt cloches upwards using a wedge to allow air to circulate.

Maintenance of Glass Structures

It is always important to keep everything clean to prevent build up of disease and pests. At the end of every growing season clean everything thoroughly. Throughout the growing season ensure the removal of dead or diseased plant matter to prevent contamination. Always repair broken parts to ensure the correct workings of the structure and also to prevent any injuries.