Plants and Water

• Most established landscape plants need about 1 inch of water per week to remain healthy, according to the University of Illinois Extension Service. The 1-inch total is rainfall and irrigation combined. Supply this moisture through deep, infrequent watering for a couple of reasons: deep watering promotes deeper root growth and thus, stronger plants; and it curbs the loss of a significant amount of moisture to evaporation.
  
  

Timing is Everything

• Most plant and conservation experts recommend early morning watering for outdoor plants. This allows the deep penetration of water without the evaporation that comes with mid-day heat. This also is the time of day when winds are less prevalent, further discouraging evaporation. As a result, your plants receive what they need, using less water overall. If early morning watering is not possible, late afternoon is the next best choice. Water early enough for the foliage to dry out before dark, as wet foliage promotes the growth of some fungi.
  
  

Avoiding Leaf Sunburn

• A 2010 study published in the New Phytologist showed that certain plants can suffer sunburn when watered at mid-day. Water droplets left on leaves exposed to direct sun can magnify the sun's rays and cause damage to the leaves. Smooth leaves are less affected by this phenomenon than leaves that have microscopic hairs.