On average, the amount of water we use in our gardens is a relatively small proportion of overall household water consumption. However, this usage tends to be at the hottest, driest times of year - when water supplies are at their lowest ebb. On a summer evening, as much as 70% (over two-thirds) of all water being used is going into gardens - from hosepipes, sprinklers and so on. Using drinking-quality water on plants and lawns is rather a waste of the effort taken to clean and filter our mains water anyway, but it is especially so at times when that supply is stretched.
As we start to feel the effects of climate change, droughts are expected to become more common - particularly in eastern parts of the UK. Sudden, short periods of high rainfall are also expected, but if the soil is parched these are more likely to damage than replenish. There are a number of actions you can take to help reduce the amount of water used in your garden whilst still protecting your garden in dry weather:
Keeping water in the soil
Soil that contains a high proportion of organic matter will retain moisture better, so use an organic fertiliser such as horse manure or make your own compost. Mulching reduces the rate of evaporation from the surface, encourages good root growth and will help prevent water being stolen by any weeds. You can use bark or gravel (at least 5cm / 2in thick), or reuse hessian-backed carpet or cardboard, or use plastic mulching sheets.
Heavy soils that can hold more water can be watered more heavily and infrequently but remember that if water penetrates more than 60cm (2 feet) into any type of soil it will be wasted. If the soil at a spade’s depth is moist then there is no need to water, but clay soils will tend to feel wetter than they are and sandy soils will feel dryer.
Collecting and storing rainwater
The simplest method is to use a water butt connected to the down-pipe that comes off your roof. It should be covered to prevent anything falling in. A diverter pipe channels rainwater from your roof and will prevent overflowing.
Reusing waste water
The water from sinks, baths and washing machines is termed ‘grey water’ and can usually be put into the garden with no problems. However, it is not possible to store this water without chemical treatment, so direct irrigation is the best course of action.
Simple diversion kits allow shower and bath water to be channelled from the down-pipe into the garden. If you want to use water from the washing machine low-sodium detergents without phosphate should be used as sodium degrades soil and phosphate can cause algal problems in any ponds or watercourses it may enter. Kitchen water is generally too dirty for reuse. If free from grease and too much food residue, cold dishwater can be used for watering larger and more established plants, but not for anything that you plan to eat.
If you water too sparingly, you can encourage shallow rooting and lose water to evaporation rather than getting it to where it is needed. Use a watering can to focus the water around the base of the stems underneath the leaves. Hoses are extremely water intensive and may even damage soil structure. If you need an automatic system try a drip or trickle system, to distribute fine droplets and so waste less. Do not use rain or grey water in a sprinkler spray, as the airborne water droplets could pose a health risk if breathed in.
To make things easier, place thirstier plants close to the water butt. Prioritise young plants and seedlings that would quickly die if neglected, and water in the morning or evening to give the plants a chance to soak up the moisture in cooler conditions. Edible leaves need to be kept watered, but established trees and shrubs should be practically drought-proof.
Hanging baskets tend to be a nightmare to keep moist. Choose ones with a built-in reservoir and don’t allow to completely dry out - as hardened compost makes it difficult for water to infiltrate. Remember that larger containers are better than smaller ones.
Lawns are greedy creatures, but if left under-watered will usually be forgiving when the rain returns. Spiking your lawn will reduce run-off by mitigating compaction of the soil and improving drainage. Longer grass is less likely to scorch, and reduces water lost from the ground - an excellent excuse for not mowing the lawn so often!
In naturally dry soil try planting Mediterranean plants such as lavenders, cistus and oleander, or oriental grasses and succulents. Perennials that will cope with dry conditions include artemisia, brachyglottis, dianthus, echinacea, purpurea, iris and papaver orientale. Pelargoniums and petunias are also pretty drought-resistant, or if you want to avoid any worry about watering why not plant a wild flower meadow or leave an area of rough grass as a wildlife haven.
On the vegetable patch, French beans, beetroot, chard, carrots, parsnips and cabbages are more resistant to drought, and if you choose sweetcorn and pumpkin you can get away with not watering at all. You may wish to avoid green leafy vegetables that need more water, such as lettuces, peas, cauliflowers and broad or runner beans. Good root growth means that plants can more fully explore the soil for the water available in it. During flowering roots stop growing, so plant before flowering. Plant in autumn or spring so that the soil isn't being disturbed during the dry season.