When to quench a plant's thirst Despite childhood memories of running through sprinklers on lush turf, the days of indiscriminate water use are over. Conservation is the gardener's watchword, and by following a few easy guidelines, you can maximize the value of the water you do use.        The best time to quench your plants' thirst is early in the morning, when plants are turgid and best able to take in more water; in fact, the morning dew that moistens the top few millimetres of soil makes it easier for water to penetrate deeply. Irrigating at midday is wasteful, as much of the moisture is lost to evaporation, while watering in the evening isn't ideal because leaves stay wet all night long, which can lead to disease.Although traditional wisdom dictates that the average garden needs about 2.5 centimetres of water per week, variables such as soil type (for example, sandy soils dry out more quickly than clay), weather and the moisture requirements of individual plant species mean gardeners must tailor their watering to specific conditions. Specimens that look limp or wilted in the early morning or evening should be watered immediately-these are signs of stress and cellular collapse, a stage at which rehydration is difficult. Plants consistently deprived of moisture for too long will become more vulnerable to attack by disease and insect pests.As a general rule, it's best to water less frequently but deeply; a light sprinkling will evaporate quickly and therefore fail to reach plant roots. (Test moisture depth by digging out a divot-15 centimetres or more is ideal.) A thorough watering also encourages plants to send their roots down into the soil where moisture is stored, rather than relying on surface water, which can be irregular.The most efficient way to deliver moisture is by applying it at ground level. A porous soaker hose laid around the base of plants allows water to seep slowly down to the root zones without moisture loss due to evaporation or runoff. Once the hose is positioned, mulch can be added overtop to hide it and keep moisture from the evaporating rays of the sun. Drip irrigation systems are another option, but they are more costly to install and the tubes sometimes have a tendency to clog. For large gardens, it may be more practical to use overhead watering systems, with either in-ground or hose-end sprinklers. Quick facts Quick fact 1Most plants need more hydration at critical times in their life cycles, such as when they are young and growing quickly, after transplanting, while setting buds and when fruit or seeds are developing. Note that shallow-rooted plants need closer monitoring for signs of dehydration than deep-rooted specimens, which are better able to tap into groundwater.Quick fact 2It's a myth that water droplets act as lenses on plant tissue, causing scorching; if it were true, plants would be reduced to smouldering heaps when the sun comes out after a rain shower! Be a water miser Be a water miser1 Install a rain barrel to capture water fromeavestroughs.2 Control weeds, which compete with garden plants for moisture.3 Mulch to slow evaporation from the soil, cool the surface and discourage weeds.4 Repair any leaks in couplings, hoses and sprinklers.5 Grow drought-tolerant plants native to your region, and group those with similar watering requirements.6 Recycle water from dehumidifiers, air conditioners and household grey water.7 Position sprinkler heads to reach target plants and avoid paved areas.8 Add organic matter such as compost and shredded leaves to improve texture and the water-holding capacity of all soils.9 Stop watering when runoff occurs.10 Invest in rain sensors and moisture meters for watering systems.