The equipment you'll need

The beauty of a glasshouse is that it enables you to completely control the environment in which your plants will grow. We’ve listed below some of the equipment you may need for your greenhouse, sorted by the type of environmental control they give you:


Controlling humidity enables you to reduce the moisture plants lose through transpiration (the higher the humidity the less moisture loss) and cools cell tissues within the plant. However,  high or low humidity can encourage particular pests and diseases, so it’s important to get the balance right.

High humidity is often required for the propagation of plants by cuttings and is managed by fog or misting benches; enclosed environments where an overhead applicator sprays out a fine fog or mist. A mist consists of droplets which are larger than 10 micrometres and achieves 85-90% humidity. Fogging involves smaller droplets (less than 10 micrometres) and provides 95-100% humidity. The smaller droplet size formed by fogging uses less water than misting and can cause fewer disease problems (eg fungal infections) as they don’t get the leaf surface as wet. The level of humidity required depends on what you need it for (eg fogging is better than misting for cuttings which are larger or were taken earlier in the year).

A simpler (though less effective) way of increasing humidity is to ‘damp down’ the greenhouse by pouring water on the floor within the greenhouse. The water then evaporates into the atmosphere around the plants, raising the humidity level. It’s particularly important to do this on hot days. In a small structure you can hand spray water over the plants or simply leave a bowl of water topped up in there which can gradually evaporate into the air.

Individual plants (such as cuttings) can be provided with additional humidity by being grown in propagators (which have clear plastic lids to cover the plants) or by putting a clear plastic bag (eg a freezer bag) over the pot, ensuring that it doesn’t touch any leaves as the condensing water can cause rot.

To reduce humidity, increase the ventilation of the structure so that the air in the glasshouse moves around more and pulls moisture away from the plants.


You should aim to have as much light as possible to maximise photosynthesis, without causing scorching of plants. Different types of structures bring in more or less light. However, you can take steps yourself to manage light. Shading paint, blinds or screens can help to shelter plants (particularly vulnerable seedlings) from the intense light of a summer’s midday. If you want to increase levels (and this is generally only done on a professional level,  but you may wish to use lighting to improve plant growth or increase the day length for photoperiodic responses) you can purchase high pressure sodium, metal halide or mercury lights to provide additional lighting.


The required temperature within your glasshouse will vary greatly depending on what you want the glasshouse for. For photosynthesis the ideal temperature is between 25 and 36°C, but photosynthesis will take place within the wider range of 10 to 45°C. For propagating you generally need a temperature around 18°C. Often, particularly if you’re propagating plants by cuttings, you will want the air temperature to be 5 to 10°C cooler than the temperature of the roots. If you’re just using the glasshouse to overwinter tender plants then you simply need it to remain above the minimum temperature for that plant. So you really need to know what you want to grow before you invest in temperature controls!

Keeping a thermometer in the greenhouse will help you control the temperature. Thermometers which record the minimum and maximum temperature will enable you to track the temperature over the course of the day and ensure it isn’t getting too hot or too cold. Wireless thermometers can enable you to track the temperature without going outside; you place a probe in the glasshouse and keep the receiver (which tells you the temperature) in your home.

These are some of the ways in which you can control temperature:

  • Increasing or reducing ventilation levels will reduce or increase temperature respectively. This can be done by vents in the roof, louvre vents in the sides of the structure, extractor fans and/or by opening the door on hot days (don’t keep the door open on windy days). Automatic vent openers can be used to control the ventilation depending on the ambient temperature.
  • Shading (with blinds on the roof, shade cloths hung as a ‘false’ ceiling or shading paint) can help to reduce temperatures.
  • Watering, misting or fogging with cold water can help to reduce the temperature around the plant’s rooting area.
  • Heating devices can warm the air, some (eg electric heaters) have thermostatic controls so they turn on and off when required, others (such as paraffin or propane gas heaters) are on all the time (albeit that you can control the heat levels to some extent) and are often only used for nighttime heating. Electric fan heaters are particularly useful as they are thermostatically controlled to provide heat when you need it, plus the fan motion helps to move the air throughout the structure. In larger greenhouses a piping system can be run along the walls through which warm air or water is pumped.
  • Heated propagators, soil warming cables or an organic ‘hot bed‘ (if the structure has soil borders) can provide the bottom heat to the rooting area that cuttings require.
  • Frost alarms can be fitted, which will sound an alarm (which is usually within your house) when temperatures are dropping so you can go and protect the plants.
  • Insulation can be provided to retain heat, such as bubble wrap (double or triple skins of polythene with air trapped between them) used to add a secondary glaze or thermal screens drawn across the width of the greenhouse to prevent the hot air rising up and escaping through the roof.


There are many different ways in which water can be supplied to plants. Be aware that many plants don’t like to have wet foliage, so they should only be watered from below. These are some ways of providing water to plants in glasshouses:

  • Watering can and rose.
  • Capillary matting (a felt like material that sits under pots and absorbs water while still making it available to be drawn up by the plant)
  • Spray system (providing overhead watering)
  • Drip feed (individual drippers provide water to specific spots)
  • Seep hose (a good option for a border)
  • Ebb and flow (more often used on a professional scale, this floods the bench where the plants are standing for 20 minutes and then drains)
  • Fogging and misting systems (see humidity) also provide water.

These can either be controlled manually or by automated systems. The automated systems generally work on a timing basis (ie providing x minutes of watering x times a week) but more expensive devices can also be used which are based upon maintaining a certain soil moisture and/or humidity levels.

Don’t forget to collect rainwater from the greenhouse’s gutter, this can provide a very convenient source of water for watering.

Carbon dioxide

Plants require CO2 to carry out photosynthesis, so it’s important that you maintain levels of this gas within your structure. In professional situations this is done by piping in CO2, but this isn’t necessary on an amateur scale. Ensuring sufficient ventilation (through roof vents, louvres, extractor fans and/or opening the door occasionally) should allow enough CO2 to move into the glasshouse. A propane gas heater will produce CO2 as a by-product.

Positioning your plants

The principle use of the glasshouse will dictate the way in which you will position your plants. If you wish to simply grow plants in the borders of the greenhouse, or in growbags/large containers sat on the floor, then you will need no additional equipment. However, if you are using the space for propagation and/or for overwintering a large number of plants you will need tables to keep them on. In greenhouse-speak these tables are called ’staging’.

Staging comes in two main forms, either permanent, built-in staging which is fixed to the structure, or free-standing staging which can be moved around according to your need. Staging is usually between 75 and 90cm tall, to allow you to work at it (eg as a potting bench), though lower staging would be needed if you will be working sitting down. Plants are then place both on and under the staging.

The staging may have a solid surface (which is useful for placing capillary matting on) or can be slatted/mesh to allow for greater air flow.

Shelving can usually be fitted to the walls of greenhouses (with specialist fixings for aluminium and steel framed structures) to provide additional space for plants or equipment.