This is the time of year that you can damage your landscape by watering too much.
Water comprises 80 to 90 percent of the fresh weight of grass and it also plays a fundamental role in the plant metabolism. Only one percent of water absorbed by plants is utilized for metabolic activity. The majority of water absorbed is used for transpiration. This is a plant process in which water is absorbed by the roots, passed through the vascular system, and exited from the plant via the stomata into the atmosphere. Transpiration helps maintain plant temperatures by cooling through the latent heat of vaporization. This process helps to warm plants during freezing temperatures as the water evaporates around them. The water absorbed by the plants in the transpiration process also brings nutrients from the soil into the plant. This is one of the reasons the plants look so much healthier after a good rain.
The amount of water transferred into the atmosphere by evapotranspiration from turf surfaces is governed by a number of environmental factors. Sunlight, relative humidity, temperature, wind and available soil moisture are all elements. Minimal ET rates occur when there are dark, cloudy days with high relative humidity, low temperatures and no wind. These are the usual fall and winter weather conditions. Maximum ET rates occur on bright sunny days with low humidity, high temperatures and high winds.
According to a table computed by the United States Department of Agricultural Soil Conservation Service June through September have the highest evapotranspiration rates. These are months which also have the highest irrigation requirements if we don't have adequate rains. The cooler temperatures of winter cause plants to become somewhat dormant. This affects the rate of water use by plants with decreased transpiration as well as lower evaporation from the soil. A general rule used in Florida is to apply 3/4 to 1 inch of water one to two times a week in summer and once a week or once every two weeks in winter.
It is true that too much water can cause damage just like too little water. Excess water symptoms are similar to symptoms of not enough water. Under conditions of excess water the soil lacks the oxygen needed for root survival. As the root system deteriorates, the plant takes up less water leading to brown grass blades. Often the decline of the root system is followed by invasion of root diseases. If plants with adequate moisture in the soil show what appears to be water stress symptoms, the root system should be examined for rot and disease.
Prevention with good horticultural practices is the best method of disease control in the landscape. Just like humans plants will become sick and diseased if they aren't properly cared for and nourished. If you suspect disease, you should send a sample of the grass to the University of Florida Plant Disease Clinic to identify the proper diagnosis and recommendations. Second identify the conditions that might be promoting disease development like areas previously stressed by lack of water or improper use of insecticides or herbicides which can burn turf. Mowing too short or infrequent mowing can stress the grass when you cut off too much of the blade at one time. Inadequate fertilizer will also leave a lawn with little defense to fight infection. Then when water is present for too many hours the disease begins to multiply and spread. Over watering in the winter and heavy rains in the summer can both be a trigger for disease out break.
The months of November, December, January and February are almost always cool enough to really cut down on those water bills. A web site you might find helpful is http://edis.ifas.ufl.edu/LH079.http://turf.ufl.edu.Eileen Ward and her husband Peter have owned and operated Greensward of Marco, Inc., a lawn maintenance and landscaping company since 1981.