Sunday, September 11, 2011

Watering Trees in The Woodlands, especially during a drought

One stand of  trees die in the forest among others that survive

How to water trees in Southeast Texas applies to more than the Woodlands, but tests were run here, and I have had good enough success and failure to bring recommended methods forward and proclaim some best practices. I did this because of the generalities published elsewhere and the usual assumption that a tree stands by itself. I contend that life in our forests has some trees depending on others and all trees competing for moisture. Some trees are more resilient than others when it comes to no available water supply. This article is not only about watering a tree; it is about watering a forest. The photo above shows a stand of trees that died due to beetles and drought. Drought weakens the trees so that the beetle can attack it. Disease is often the result of drought. Healthy watered trees will have a 200% water content but a drought stressed tree will have half that.

This summer has been especially extreme through high heat, little rainfall and at times extremely low humidity. That combination causes fire danger AND threatens the lives of our trees, bushes and plants that normally can survive normal drought. During my experimentation this summer, I lost considerable turf in my yard trying to see where the threshold is on watering my trees. We have been under water conservation measures, confined to one inch of water per week, with two specific watering days allowed. Ours has been Thursdays and Sundays. You are allowed to hand water at other times, to keep your garden flowers from withering away and to care for special areas that may not survive the twice-a-week schedule. With these constraints, I worked out various ways to keep the trees alive.    

I have lost no large trees that were healthy before this summer dry season, but lost most of the trees planted on Arbor Day this year, half of the trees I planted last year and even a few trees planted three years ago on Arbor Day. I have planted and cared for trees in public areas as well and believe I lost some of those this summer. So why do I start with the trees I lost? Finding the balance between conservation of water and conservation of species is difficult, but my issue was mostly with trees already suffering from disease and past droughts, not necessarily my practices, except for one tree I never dreamed I would lose.  

Of utmost importance have been the 20+-year-old trees in my yard. These have been a priority. They are not replaceable without considerable expense. The 40-50 year old pines are huge. I would really hate to see them go! To cut one dead tree down of this size would cost nearly $1000.

So, here are the methods I have tested and proven to work. I can tell that these methods and strategies work by comparing with my neighbors who do not have such strategies. My neighbors had less loss than the surrounding green areas of forest, but they lost healthy big trees - mostly Oak and Pine. I did not.

Bucket Method

The bucket method  
I went to a local general store to purchase 12 5-gallon buckets. For me, I chose Home Depot because I happened to be there for some other reason and saw exactly what I wanted for sale. Spending about $30, I took them home and tested one with three small holes drilled in the bottom.
That turned out to be too much of an outlet, so I drilled one small hole in the bottom of each of the other buckets (about 1/8 in. drill bit) near one side of the bucket, not in the center. You need the flexibility of placing the hole near a small tree, so the hole was placed on the perimeter of the bottom, not the center. Water is pulled by gravity into the ground, so the area directly beneath the hole is place where the water will go.
Bucket configuration for one tree
     So I started using this method to water my Magnolia tree. Both of my neighbors lost their Magnolias. After I started this technique, mine became much healthier and now the larger one flourishes. The buckets are placed at the drip line of the tree. Note how uneven the configuration is above - that represents the outline of the limbs on that tree. Typically, an established tree will have roots branching out in the mirror image of the tree, under the ground about 4-6 inches. Many times we train our trees to root just one-two inches under the ground and even on the surface itself. That will dry out in three days under normal summer conditions. Where the tree can normally find water, that is where its roots go. Such a broad statement has it's exceptions as you might imagine. Hard clay soils tend to push roots to the surface and soft sandy soils lends itself to deeper rooting, but the rule still applies. I personally have both  situations in my yard. If watered frequently and shallow, the roots will depend on water being available all the time in shallow soil. The general recommendation by noted experts is to water every 10 days. I agree with that in times of severe drought. In times of exceptionally high temperatures, low humidity, and wind, smaller trees really need more frequent deep watering, as often as every 5 days. I normally do not water for two weeks or more if we get an inch of rain. This summer that has not happened one time! Before I left on vacation, just before the 100+ degree temps, low humidity and wind arrived from Tropical Storm Lee, I watered all my trees using the bucket method. Nine days later when I returned, there was no damage except my 15-foot Bald Cypress went brown like it does each late summer. It always comes back when the temperature is more moderate and the rain begins. By watering it when I returned, the browning immediately ceased and the tips of the branches remain green to this day.        
Using buckets for a random forest configuration of trees - canopy intersections

The bucket method is also good for forest areas, although a forest floor is best is it is generally with an inch of water soaked once every month, it will survive with the buckets every 10 days. Where the canopy of one tree intersects with another is a good place to place a bucket.

Remember that some trees are more  resistant to drought than others. My small 3-year-old Magnolia in the green area behind my home died from lack of water, because I did not water it before I left on vacation. It did not survive a 20-day fast; neither did four small pines in the same general location. Lesson? Water the trees thoroughly before you leave on vacation and have someone else do it if you are gone more than 10 days. If the situation is normal and there are accumulations of rain that exceeds 1/2 inch, my strategy is to not water the trees at all, except if the temp is 100+ and/or I have trees that have been in the ground less than 3 years. In those cases some of the trees get watered every 5 days. Sometimes, they have to be watered just like the flowers. Just keep an eye on them and the soil.
Measuring water delivered to the trees

 General area watering method
This method is always preferred but will not allow you to conform to watering regulations. You just program a watering system to deliver one inch of water at one time to your yard. That will get sufficient water to your tree roots every ten days. I have found that a cat foot container works well to measure the amount of water delivered.  Just dip a ruler in it and see where the water line come to the ruler marks. Using a uniform delivery sprinkler works well to get sufficient water to your trees. I have used an automatic shutoff timer for this method, and it works well. This is laborious but less so than the bucket method. The full inch must be delivered in one watering, you cannot deliver 1/2 in twice a week and get down far enough for many trees. There is a way to tell if you are getting sufficient dirt wet  in one watering. I test the ground with a long screwdriver. If it won't easily go into the ground 8 inches, it is not watered enough. But again, there are exceptions. If you have a heavy clay over your tree roots, You may not be able to get sufficient water that deep. Exceptional situations warrant exceptional processes. Just use common sense, but stay within the governing laws of the community.
Helical configuration of a soaker hose

Soaker Hose Method
I use this sometimes when I want a general area soaked down for a special tree. Lay out the hose beginning at the drip line and start a helical configuration towards the trunk. Never go to the trunk because a mature or aged tree is not effectively watered next to the trunk. Its roots stretch out where from where the leaves begin to the outer leaves vertically. You want the outer perimeter drip line of the tree to get the most water. This method can get expensive and cause you to use more water than permitted under neighborhood conservation measures. You can also measure delivery by placing the food can under the soaker hose.

So in general - I recommend the bucket method to conserve water and the general water method every 10-20 days if there are no constraints. I use the soaker hose for one special tree. All my pines get the buckets except for an occasional general thorough deep application by sprinkler or hose. This summer I applied of these general watering applications for the trees.

References - I have read many articles and seen several videos on this subject, as well as heard the experiences of others. I have no specific sources for you to access. These are my conclusions from the experience I have personally acquired, added to my own [past experiences and observations. Read related articles in the Commentary for additional insights and observations. If these methods do not work for you, I am sorry. I am only sharing what I have experienced and know works for me and my yard and has for over ten years.

Post publishing note: A question was asked me on email about the beetles. Apparently I have not identified the primary species of beetle that kill sour trees in Southeast Texas in prior articles. It is the IPS beetle, not the Southern Pine Beetle but we do have Southern Pine Beetles here and they do damage our trees.
Reference: University of Florida article on beetles, 1997 

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