Watering: A Goldilocks Dilemma
Proper watering is just about the most difficult challenge that gardeners face; especially this year with summer weather bringing record breaking heat and arid conditions that has lasted several weeks.
How a rain event works!
When asked how often to water, or how much, I always tell customers to emulate Nature; “when it rains, it pours” and usually (outside periods of drought) She provides enough rain to saturate the soil many inches down. During a normal rain event, water is absorbed, filling the tiny gaps (pore space) in between soil particles. The amount of organic matter and percentage of pore space within the soil profile determines the soil’s ability to hold water.
After a rain event concludes, in relatively short time, the absorbed water is pulled down through the soil profile by gravity, emptying the pore spaces of most of their water. Some water remains clinging to the interior of the “Pore Spaces” and exterior surfaces of the soil particles, a process known as adsorption.
With the resulting drainage, a vacuum forms pulling fresh air in from the atmosphere. It is almost as if the soil is actually breathing; exhaling the carbon dioxide and other respired gasses that have accumulated; taking in oxygen rich air, just like we do!
If the rain event continues and water can no longer be absorbed, it runs off as surface water. This is what is responsible for erosion and flooding. Areas with lush vegetative growth and deep soil can absorb tremendous volumes of water; conversely areas with compressed compacted soils or those with concrete or macadam coverings cannot absorb rain water. It’s important to understand how water penetrates the soil supporting your plants. If Mother Nature isn’t providing enough rain, then you have to supplement making up the difference.
How much water?
Established plants, those that have been there for a full year or more, generally need an inch or more of water per week during the warmer growing months. This may be accomplished with one or two waterings. The actual amount required is dependent upon the maturity, size, and type of plant material. The older the plant, the more expansive its root structure and the greater area it can access for moisture. Therefore, mature plants require more water to adequately moisten their root zone.
Younger specimens require less water than established plants per application, because of their limited root mass. They require less water more frequently. This will assure that they develop a healthy root structure that “knits” into the surrounding soil. It is important to apply sufficient water to thoroughly moisten the entire root area and surrounding soil. Because new plants have smaller root zones they require less water to sufficiently water them than established ones.
It is important to allow them to dry out slightly before watering again; allowing oxygen to penetrate down throughout the entire root zone.
A general rule of thumb for a mature tree is 10 gallons of water per inch of trunk diameter measured at knee height, once a week around the “drip-line” (circle around the plant under the outer tips of its canopy where the preponderance of the feeding roots are located).
Younger trees and smaller ornamentals will require proportionately fewer gallons per inch of trunk diameter; all the way down to 2 gallons. Newly planted perennials, annuals, vegetables and the like may require anywhere from a quart to a gallon to saturate their root zones and surrounding soil.
How are your plants doing?
Drilling (utilizing an earth auger) or digging (using a trowel) test holes around the “drip-line” of ornamentals and trees to check the soil consistency and moisture content is important in determining how well water is getting to the roots and how much is there. Smaller plants, perennials, roses, annuals, and vegetables should be checked 2 to 4 inches deep; larger trees and ornamentals 6 to 8 inches deep.
If the soil is still moist, don’t water, if dry irrigate around the drip-line area with sufficient water to moisten the soil to the level you checked and slightly deeper. You always want to drive water deeper than the roots penetrate. This assures a deep well established root structure. Drilling additional holes to the correct depth will assure water gets down to the roots where it is needed. Leave the holes open to increase oxygenation of the root zone. Remember plant roots and the soil mycorrhiza and beneficial bacteria need moisture and oxygen to thrive. The secret to successful gardening is to balance the two.
Too much water creates anaerobic conditions depriving the soil of oxygen and causes a buildup of carbon dioxide and other harmful gasses. This brings about plant stress, disease, and other maladies that contribute to unhappy plants.
How best to deliver water?
As I mentioned earlier, emulating Nature is the best way to approach anything related to horticulture.
“Slow and steady wins the race” is an excellent way to look at watering. Watering Wands with breaker heads deliver a gentle yet high volume of water. Soaker hoses, drip irrigation tubes, sprinkler hoses, soaker heads, and other like devices deliver water to root zone in a controlled adjustable manner. Avoid sprinklers that wet the foliage or canopy of plants. This wastes water and may encourage disease causing organisms to gain a foothold. Use timers to regulate the amount of water being delivered. You can’t over water in a single application, but you can waste water or conversely not deliver enough water to thoroughly saturate the plant’s root zone. Use overhead sprinklers, oscillators and impulse types, for lawn areas only. Time them to deliver enough water to penetrate the soil deeper than the roots go once or twice a week depending upon temperatures. Newly seeded areas will require very frequent shallow watering to maintain adequate moisture for grass seedlings.
What time of day is best to water?
Plants utilize water for many things; nutrient absorption, uptake, and transportation, turgor pressure (keeps plants upright), photosynthesis and related activities, evaporative transpiration (cooling system), and many other metabolic processes. The majority of all of this activity occurs during the day when the photosynthesis is taking place, so early morning is the best time to water. Avoid watering in the evening or at night if at all possible. This prevents the roots from sitting in waterlogged soil overnight. Do not wet foliage overnight which would encourage fungal disease problems. Also try to avoid water droplets on foliage during the strong daylight to prevent leaf scalding due to sunlight magnification.
As with many things in life, timing is everything! Proper watering techniques, frequency and duration along with other good gardening practices will assure success in your yard.
Success with your gardening, Naturally.
Written by Rick Stecher
Garden Center Manager