Turn off the water works

Water meters are on the way, so it's especially relevant to know how to use water responsibly in the water, writes JANE POWERS.

THE OTHER DAY when I was out walking I saw someone watering a patch of bearded irises, waving the hose around so that it made a big lazy arc. There were two things wrong with this scene: one, bearded irises don’t need watering, and two, swirling the hose about is not an effective way of delivering moisture to where it is needed – at the roots of plants. I resisted sharing these facts with the hose man, because I am wary, as I enter middle age, of the increasing possibility of appearing like the neighbourhood nutter.

So, instead, I’d like to devote this column to some thoughts on water-wise gardening. A few years ago, if you mentioned saving water in Ireland, where in certain parts, rain is a bit like outdoor wallpaper, you’d be met with incredulous looks. But now, most of us are aware that the stuff that comes out of our taps is a precious commodity. This is especially true in areas such as Dublin, where development has put pressure on our reservoirs. The recent dry spring has further depleted water supplies and dried out the soil.

There are loads of different ways of conserving moisture in the garden, and reducing our dependence on tap water. They include collecting water, improving and minding the soil, choosing the right plants, and watering strategically.

Free water

If you have a roof, you can collect water. An average house, for instance (with a footprint of 50 square metres), can supply over 20,000 litres per year of rainwater. Because most of this falls in winter, you may need a large storage tank, but even a water butt will save your turning on the hose quite as often. Greenhouses, garages and outbuildings can also be fitted with water butts. You can also re-use cleanish water from the house, such as that used for salad and vegetable washing. Catch it in a basin, instead of letting it run down the plug hole. If you’re really dedicated, you can siphon bath water out of a window (this is quite fun – once in a while). And if you are building a new house, do consider fitting it with a grey water and rainwater recycling system.

Mind that soil

The way you look after your soil can make a difference in the amount of water it can store. Town gardens often have dry, light soil that dries out quickly. And some soil surfaces are susceptible to panning, where a top layer of fine particles forms an impenetrable crust, so that water rolls off it. The ideal soil acts as a sponge, absorbing a great volume of moisture when it rains, and then gradually releasing it over a long period. The key to creating this kind of structure is organic matter, usually in the form of compost or well-rotted manure. Regarding manure – never use fresh stuff, as this can harbour E. coli or other pathogens. Composting in a hot heap – 60 degrees Centigrade for up to two weeks – is supposed to sterilise manure. However, just to be sure, many growers (including me) no longer use manure on food crops. When using it in flower borders, or to mulch roses and clematis, be sure to wash your hands well afterwards.

I add garden compost to my soil by layering it on the surface, and letting the worms dig it in, and by incorporating it when planting. If you are keen on annual digging (I’m not), then be sure to add bulky organic matter as you go. The humus makes the soil more water-retentive, and more lively and healthy. Mulching the soil after watering or after rain helps to lock the moisture in. Organic mulches – such as grass clippings, leaf mould, straw and composted wood chippings – rot down in time, and condition and feed the soil. Inert mulches such as gravel, grit or pebble are more ornamental and look well in Mediterranean-type gardens.

Right plants

Plants from arid regions or from habitats with drying winds and sunshine (including the seaside), rarely need watering. Their leaves and stems are modified to prevent moisture loss. They may be grey or silvery, as in seakale; waxy or leathery (bergenia); hairy or furry (Phlomis); swollen (succulents such as sedums); or fine-foliaged (thyme and rosemary). Verdant, velvety lawns are fierce water hogs, but grass, in fact, does not need watering – unless it is in its first season. True, an unwatered lawn may go brown, but it greens up again when rain falls. Very short grass allows the soil to dry off underneath, so if you’ve been scalping your lawn, raise the blades of the mower.

Watering well

Water all plants really well when you plant them, apply a mulch, and keep an eye on them while they establish (trees and shrubs may need monitoring for two years or more). When you water, be generous: water deeply and infrequently, instead of little and often, as the latter promotes shallow roots, which are unable to resist drought.

Sprinklers are the least efficient way of delivering water, unless they are set low, and near to where the moisture is needed. A so-called “leaky hose” (which has perforations) is much better. Food crops require regular watering, so don’t skimp there – but be sure to mulch the soil.