Prepare your greenhouse for spring

With fewer outdoor gardening tasks to be done, winter is the ideal time to reorganise your greenhouse, in preparation for spring. By de-cluttering, having a thorough clean and adding a few items of kit, you can create the optimum growing conditions for your crops.

Choose a full day and start by having a good clear out, evicting all the things that shouldn’t be there. Next, gather together all the useful kit you have and give it a clean.

Once you've cleared and cleaned, you can take stock of what you need for the growing season ahead. Discover how to ventilate, shade and heat your greenhouse, below.

Add greenhouse vents

Insufficient ventilation is one of the main reasons why greenhouse plants suffer from fungal diseases. To combat this, you need to ensure there are enough openings, and that they’re positioned correctly to allow good air circulation through the greenhouse. Ideally this would include two slatted vents located low down on either side, and two roof vents at the top.

If you can, invest in an automatic vent-opener. On hot days it could be a life-saver for your plants. If you forget to open the vents for any reason, the automatic opener will ensure that hot air can still escape, preventing plants from shrivelling.

Use shade netting

In summer, you need to protect plants from harsh sun, so invest in shade netting to throw over each side of the greenhouse. You can also fit indoor blinds, but these are expensive and may knock into pots and growing bags.

Install electricity

Installing electricity in a greenhouse is expensive, but is well worth it as it opens up so many possibilities. Not only will it allow you to have a good light source to work by in the evenings, but you can also plug in a propagator or heated mat, which means no more trays of seedlings cluttering up the house. It also allows you to run an electric heater with a thermostat, which only uses power when you need it.

The high cost is due to the fact that you need a qualified electrician to install power. Don’t do it yourself – not only is it illegal, it’s also very dangerous.

Generate heat

A source of heat will extend your growing season and increase the range of plants you can grow. If you have a power supply, a heater with an automatic thermostat will do the work for you. To keep the greenhouse frost free in winter, aim for 4°C or above. If you don’t have power, you can use a greenhouse paraffin heater, although these need attending to usually twice a day. You can also use a propagator as a 'greenhouse within a greenhouse', providing added protection.

Maximum-minimum thermometers are invaluable – but buy two so you can monitor temperatures at either end of the greenhouse, and then position your heater where it will be most effective.

Store water

Plants in greenhouses need much more water than those outside, so be prepared. Most also prefer rainwater to tap water, so a water butt (or two) connected to the downpipes is a good idea. They’re easy to install, along with gutter kits that fit a wide range of greenhouses.

Keep a bucket filled with ambient-temperature water – chilly water from outdoors can give plants a shock. It’ll also boost humidity on hot days.

If your outdoor tap is some distance from your greenhouse, run a hose to it, fitted to a post. It’ll save you carrying lots of heavy watering cans.

Buy growing bags

In a greenhouse you have three main options on where to grow your plants – in pots, growing bags or border soil. Border soil needs regular replenishing or sterilising to prevent pests and diseases building up, so using growing bags and pots is often more sensible. Once you’ve harvested the crops, you simply add the spent compost to the compost heap and start again, with no worries about soil-borne diseases lingering into following years.

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Talkback: Prepare your greenhouse for spring
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trigger20 07/01/2012 at 19:56

I got my first green house last year and grew tomatoes which unfortunately got blight. It was mentioned that i should have used tap water instead of rain water. Is there a possibility this disease will carry through into this year if I grow a tomato crop again. Thank you

Lulu3 06/03/2012 at 19:24

In relation to automatic vent openers, be aware that on a windy day, with sun, the windows will open automatically and the force of the wind can whip out the glass - as happened to me!

nmcbride 02/02/2015 at 16:06

The max/min thermometers with some type of alarm are key. Our greenhouse is just in the backyard so I use this system - -.

The chime just keeps going off until the temperature problem is resolved.