Improper watering is the leading cause of plant fatalities.
Proper watering of a newly installed plant or landscape is critical to their successful establishment and future growth. Though watering may seem like a simple task, it is a complex subject that does not easily offer a "one size fits all" guideline for the quantity and frequency of watering.
Roots need water to survive, and to supply needed moisture above ground for photosynthesis. However, it is critical to understand that roots also need oxygen in order to function. Never allow the soil around the roots of new plantings to be too dry, and likewise, never too wet. Oxygen is not available in waterlogged soil as it occupies the same pore space as water.
How Often to Water
Plant material must be watered thoroughly at planting time. Subsequent watering will depend upon whether the plant was balled & burlapped or in a container, weather conditions, soil type, etc. Irrigation systems do not provide the appropriate amount of water at the required times for newly installed plants. A rain gauge is a wise investment if you do not have one, as 1" of rain water per week is recommended for established plants.
How to Water
This is best accomplished by setting your garden hose at the base of the plant with the nozzle removed. Let the water slowly trickle to completely saturate the soil. Root masses may be 12 to 24 inches deep or deeper; the water must penetrate that deeply. You may need to allow the first soaking to penetrate and repeat if runoff is a problem. An alternative method for large bedded areas is using a sprinkler and a rain gauge, making sure the amount of water used adds up to 1 to 2 inches.
Weather and Other Factors
Weather affects plants in ways such as evaporation and transpiration. These two processes combined are called evapotranspiration. The faster the rate of water loss, the sooner the plants will need to be watered.
Site Exposure - Shade vs. sun; north exposure vs. south exposure; high ground vs. low; and flat vs. sloped can all impact how water is retained or lost.
Hot, Dry, or Windy Weather -Plants transpire at a faster rate. Water evaporates faster. Plants in full sun transpire faster than plants in shady locations.
Day Length - Plants transpire only during the daylight. June is usually the month with the greatest water demand because it has the longest days, even though it may not be the hottest month of the summer.
Mulching - A thick layer of mulch keeps the soil cool and reduces evaporation, which reduces water needed.
Soil Type - An understanding of soil types helps in guiding you in proper watering frequency. Determining how water is retained in the soil and how the plant roots are able to take up water is critical. Essentially, sandy, well-drained soils demand a more frequent watering schedule. Plants in heavy clay soils, the most common in our area, have to be watered less frequently or the soil will become saturated, greatly limiting oxygen and thus suffocating the roots and killing the plant.
Checking Soil Moisture
Damp Soil - Feels cool and wet, but does not muddy your fingers. When squeezed, water will not run out.
Moist Soil - Feels cool and moist, but does not dampen your finers. The soil is crumbly, but not dry and dusty.
Completely Dry Soil - Dry and no longer cooler to the touch.
Plants can be divided into three broad groups based on moisture requirements:
Moisture Loving - Plant thrives in soil that is moist, but not wet. they cannot tolerate drought. Water these plants when the soil is damp.
Typical - Plant that requires an average amount of water. Water these plants when the soil is just barely moist.
Drought Tolerant - Plant can usually withstand long periods of drought, but they can grow better when watered periodically. Water these plants as soon as the soil in the root zone feels completely dry. These plants are drought tolerant after they are well-rooted (usually takes one or two growing seasons), until then, treat these plants as typical. These plants cannot tolerate wet soil.
Watch Your Plants
Learn to watch for signs and identify symptoms that your plants need water. In most cases the following obsvervations denote a lack of water, but if properly ateended, the plant should recover.
Curling leaves are usually the first indication of stress. Here, the surface area is reduced to cut down on transpiration.
Shiny leaves becoming dull. Bright green leaves taking on a blue or gray-green appearance.
New growth wilting or drooping. Older leaves turning brown, drying up and falling off.