Watering

Proper Watering

“He who controls the water controls his landscape!” Dr. Jason Grabosky, Rutgers University

If you don’t read any further than this; most of your trees need 1 inch of water, halfway out to the drip-line, once a week, during the growing season.

Our Upstate trees can be some of the most challenging to properly water in South Carolina. While our State (on average) receives 49.8 inches of annual rainfall, ranking us 11th in the Nation, because of elevation changes, the Upstate varies greatly. While the Piedmont receives 45 to 50 inches a year, and the Foothills, 60 to 70, the Mountains receive 70 to 80 inches a year (rainforest amount).

We also can experience mild to severe droughts (nothing like a desert, though). During one day this spring, while downtown Greenville recorded no rainfall, an area north of Easley received 8 ½ inches! Rainfall can even vary within a few blocks. This is one good reason to invest in a rain gauge (the gauge above can be purchased in most any hardware stores for about $3).

You should not rely on weather broadcasts (before or after the rain). You really don’t know how much water your trees have received unless you measure rainfall & irrigation for yourself.

While healthy, established trees, with an adequate mulch bed, can usually survive all but the severest of droughts, few urban trees are properly mulched, and therefore healthy. New installations require proper watering to become established, and stressed trees, scheduled for fertilization, Root Collar Extraction and Root Zone Therapy, require adequate soil moisture to be effective.

New Transplants

Transplanting will likely be the most traumatic event in your tree’s life. About 90% of installed tree deaths in the first year are due to water mismanagement; not enough or too much (often poor drainage). New installations most often require irrigation until they become established in the landscape.

This will likely take 1 to 3 years. Some trees and plants may even require ongoing irrigation. Nursery stock are likely watered several times a day. To adjust to their new environ, they must be slowly weaned off excessive watering.

For most trees, water every other day for the first few months, and then twice a week for the first year. Once a week the next year. During moist, winter and early spring conditions, evergreens will probably not require watering. Deciduous trees will likely not require irrigation once they drop their leaves in the fall.

Drip and soaker hoses rarely work. Either you have too little water, that does not reach the bottom of the root-ball (1 to 4 feet deep), or the root-ball is kept wet, wilting the leaves, rotting the roots, and eventually killing your trees.

Overhead irrigation works better. In-ground sprinkler heads, usually geared towards turf-grass, often water too frequently (15 to 20 minutes, once or twice a day) and too shallow (rarely deeper than a few inches). Your trees need water to sink all the way to the bottom of the planting hole (especially the first year) without remaining saturated all week.

The above oscillating sprinkler can be adjusted to meet most any landscape need (it can be purchased in most hardware stores for about $10). You can even stick your garden hose alongside the edge of the root-ball and run it at about ¼ the volume, until the planting hole floods.

Established Trees

Almost all established trees in the Upstate will flourish with 1 inch of water once a week (rainfall/irrigation). From the base, out; 4 to 6 feet for small trees (like dogwoods), 6 to 10 feet out for medium trees (like maples), and 10 to 15 feet for large trees (like oaks). More water less frequently is better, because the water will sink deeper to the roots, and as it dries during the week, it will help kill soil pathogens. Very few trees tolerate wet feet.

Don’t assume your trees are sufficiently watered because the grass is green. Many large shade trees die with in-ground sprinklers watering everyday. The 20 minutes once or twice a day rarely sinks past the mulch.

Besides using a rain gauge, you should also occasionally dig (with a trowel) down at least 6 inches, and physically examine the soil in the palm of your hand. Often, the soil of stressed trees have one extreme or the other. If you can make a mud pie; it’s too wet (likely, poor drainage). If you let it sift out of your closed hand, and it blows away before dropping to the ground; it’s too dry.

Almost all urban trees are stressed (if not, declining), due to topsoil stripping, grading, trenching, changes in the natural watering patterns, turf-grass & ground cover competition and soil compaction. Once your trees have an adequate, established mulch bed (1 to 2 years), and become healthy, you may not have to water (unless you have a moderate to severe drought).

Fertilization, Root Collar Excavation & Root Zone Therapy

If your established trees are stressed, fertilization will be far more effective if there is sufficient moisture in the soil. There will be little movement from the soil to the roots, and from the roots to the crown, if the soil is too dry. When it does rain, much of your fertilizer may runoff.

Since most installed trees are planted too deeply, and/or have volcano mulching, the mulch and soil can more easily be removed when there is sufficient soil moisture immediately around the base. This area should be flooded a day to two before treatment. Flooding for most root-balls will require about 2 inches of water applied immediately at the base.

Compacted soil of stressed or (early) declining, established trees can be aerated and/or air-tilled more effectively when there is adequate soil moisture. If your trees are scheduled for Root Zone Therapy, please water liberally from the base, out; 4 feet for small trees (like dogwoods), 6 to 8 feet out for medium trees (like maples), and 10 to 12 feet for large trees (like oaks), at least 1 full inch of water, a day or two before treatment is scheduled.