By Marilyn Loser: 2012 May 9
Vince Urbina, Colorado Community Forrester, recently gave a presentation on tree care during drought. “Drought is a deficiency of rainfall over a period of time resulting in a water shortage for some activity, group, or environmental sector,” stated Urbina.
Tuesday’s storm dumped .64 inches of precipitation according to the Wunderground website, the highest daily amount in the past year. In fact, we’ve only had 5.16 inches of precipitation in the last year and 12% of that came Tuesday. Sounds like drought to me. Most trees in Alamosa need supplemental water to keep them healthy.
Urbina asked the audience how much water a tree needs: 2 gallons? 10 gallons? 20 gallons? He then explained it was a trick question. Each tree’s situation is different. “Water it until it’s happy!” Urbina exclaimed.
How do you do that? Before answering that question it’s important to understand the anatomy of a tree. Most tree roots are in the top 2 feet of soil and, in a nature situation, extend well beyond the leaf canopy. The roots need water and air. He shoots for 6” of new growth each year.
Urbina suggests watering deeply (14” – 24” down) and infrequently. Water around the entire drip line (the line under the outer edge of a tree’s branches where water would drip to the ground in a rainstorm).
He outlined 3 watering methods. Drip irrigation and micro sprinklers both conserve water by putting it only where it is needed. Typically fertilizer can be applied through either of these methods. Drawbacks include the need to filter ditch water (chunks can clog tubing) and control weeds.
Using a Ross root feeder is Urbina’s preferred method. The root feeder is a T-shaped metal device about 2 feet long. You hook up the hose to one end of the T top and water comes out the bottom. You plunge the device into the soil at the drip line. If the soil is dry and/or compacted, it might not go in very far at first.
I’m now the proud owner of a root feeder and found after a couple of minutes I could push the root feeder in 16” or so. For my smaller trees, I watered at 4-6 places along the drip line for about 5 minutes each trying to soak the top 16” – 20”. For larger trees I watered at 8 places for about 10 minutes each. Was this enough? I’m not sure. I’ll check the soil moisture in a couple of weeks.
This works for established trees. But, what if you’re designing your yard landscape? Urbina strongly suggests planting trees with trees and turf with turf rather than planting trees and turf together. People often water their grass 3 times per week for about 20 minutes. This is NOT good for trees. The grass, with its shallow roots, absorbs the water and very little percolates down to the tree roots.
Most people buy container trees. Urbina likes #15 size containers that typically hold 1 ½” to 1 ¼” diameter trees (measured 6” from the ground). It’s easy for 2 people to handle a tree of this size. These smaller trees are less expensive than larger caliper trees and recover faster.
Balled and burlapped trees are another popular choice. Urbina notes, “For every inch of caliper at 6” above the soil, it takes that many years for the tree to reclaim roots lost [in the ball/burlap process]. A 2” diameter tree takes 2 years to recover.”
Plant the top of the root ball 1” – 2” above the surrounding soil, especially in clay. It’s a good idea to create water basins around the trees for the first year. About 75% of trees and shrubs sold are in containers and given daily water at the nursery.
Once you’ve planted a container tree, water it at least weekly until it is established. Then back off on the frequency – it takes some time for the tree to adjust to a new watering regime. Mulching under the tree canopy conserves water by reducing evaporation.
A future article will discuss the trees Urbina suggests for Alamosa. Meanwhile, visit AlamosaTrees.net for ideas.
6th Street tree planting – Saturday, May 12, 10 am: Join the Alamosa Tree Board and Department of Parks and Recreation to plant trees on the south side of 6th Street between San Juan and Ross. We were unable to plant trees along 6th Street during Alamosa Arbor Week due to utility line conflicts. The utility lines have been marked and planting locations worked out.
“We may not be able to clean up our cities overnight, be we can start to make a difference by making them greener places. Planting a tree may be the simplest, most immediate, and most effective way to make a personal commitment to the environment.” Graham Nash