16:43 - 06 April 2011
The very best way to water a greenhouse is to attend to its needs daily and employ the help of a neighbour during absences. Ideally install an outside tap outside the greenhouse and also inside to provide a mains supply for use on your plants, this avoids the need to carry heavy loads of water around the garden and makes watering quicker and more efficient. While it is far more sustainable and eco friendly to collect rainwater from the greenhouse roof via gutters and waterbutts, this water is not suitable for watering seeds and seedlings as it can contain fungal and pest spores and eggs that may affect your plants. A waterbutt and a mains supply is the ideal combination as the rainwater is good for watering mature plants and also ideal for watering plants growing around the periphery of the greenhouse, outside.
Remember that your mains water supply needs draining and disconnecting for the winter and your outdoor tap and pipes need protecting from freezing conditions even if you think they have been drained.
Once you have water on tap at your greenhouse it makes watering so much easier, but it also probably makes you a little complacent. Don’t take the water supply for granted, every drop is precious and needs to be used with care and respect. During the early months of the year your greenhouse will require gentle watering as it is important not to over water seeds, seedlings and young plants that can become waterlogged and will rot. You can usually achieve this using a watering can or bottle fitted with a watering rose. As the plants start to grow in earnest they require more and more water and as summer approaches and the greenhouse gardener it tempted to a weekend or even a week away, the problems start. Fortunately it is easy to install an automated watering system and by using micro irrigation you can tailor the watering to suit exactly what you are growing in the greenhouse, from large pots, planters or growing bags of tomatoes to small trays of seedlings and more. These kits are completely versatile and are designed to deliver exactly the right amount of water to where it is needed the most, i.e. at plant root level.
For greenhouse beds and borders a perforated hose can be installed either under the soil surface or around your plants and then connected to the greenhouse tap.
By adding an automatic timer you can arrange for the greenhouse to be watered before dawn or after dusk so that the plants are not in bright sunlight and there is less risk of scorching the leaves. You need to remember to switch the tap on before you leave and it’s always a good idea to do a dummy run, especially if you are going to be away for more than a few days. You can even buy moisture sensors that switch off the system if the compost is too wet, this is especially useful if you plan for hot weather but in fact it is dull and overcast during your absence.
By planting mature plants into large tubs and planters you reduce the need for regular watering and remove the stresses caused by your plants drying out. Terracotta pots dry out faster in hot weather than plastic ones as the water can evaporate at the pot surface (unless they are glazed). You can also add water retaining gel or crystals to your planting compost that help hold moisture in the soil and release this to your plants as the compost dries out. A mulch over the top of the compost surface such as gravel will also help to prevent water evaporation at the surface and keep the compost moist for longer.
For large pots and planters use water trays that will catch any run off from the pots and allow the compost to draw it back up into the pots. If you are going to be away for a few days watering trays can hold a fair amount of water and make a good short-term alternative to micro irrigation. Self-watering trays with a water reservoir that is fed to the compost via capillary matting is also a useful way to water plants for short term absences and in hot weather.
