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Tree Basics - updated 9-7-11 SPECIAL TEXAS DROUGHT INFORMATION: It has finally cooled down so now is a good time to water thoroughly and then just leave the tree alone, Every 4-5 days between irrigation is better than more often. If you did not soak all the roots past the dripline this year you probably had some leaf burn. Trees are amazing complex living things that can live for hundreds of years, all in the same spot. Trees need sunlight, water, carbon, oxygen, and 13 minerals from the earth. Sunlight is captured by the leaves and the photosynthesis process then manufactures sugars and starches, which is the food for sustaining life and growth. Water is mostly absorbed through tiny root hairs and is used throughout the tree. Carbon is used in photosynthesis and comes into the plant as carbon dioxide only through tiny holes in the leaf and stems. Oxygen is taken in through the roots and is also used in the conversion of sunlight into energy. Ideal temperatures for all this chemistry is 70 to 85 degrees Fahrenheit. (Trees are not as quick as humans so a better gauge of ideal weather would be a 14-day moving average of ideal temperatures and less than 2 weeks since a rain, moderate to high humidity, and light winds). The minerals needed for growth are found in the soil and are dissolved with water and enter through the tiny root hairs and then transported up the tree to the leaves. Trees also transport food from the leaves back down the tree to the roots. Tree cells, like the photosynthesis molecule and root hairs, do not last forever and replacement cells are constantly being created. Added fertilizers requires the tree to use energy to convert the added minerals, thus temporarily weakening the tree. Texas Heat 1. When it is too hot the tiny holes in the leaves will close to save water but this also prohibits the capturing of carbon dioxide. Further, when the leaf holes are open and water vapor is escaping this helps to cool the leaf. So while the leaf holes are closed, temperatures get much hotter inside the leaf and photosynthesis is in jeopardy without carbon intake. Leaf temperatures in the sun are much hotter than the reported temperatures in the shade. Texas weather is brutal but it is usually still possible to get some growth in the mornings before it gets too hot. Newly planted trees will suffer the most so keep them wet. 2. Besides the detrimental effect of hot daytime temperatures is the nighttime temperature which controls the timing of another process, the converting of the photosynthesis foods into energy molecules like enzymes and proteins that the tree needs. When nighttime temperatures are above eighty degrees Fahrenheit the tree's reaction is to put the conversion process into overdrive, so the tree is then either wasting its effort or slowly starving. High temperatures thus leads to not having the food or energy to produce new root hairs, replacement photosynthesis cells, etc. and can slowly starve plants to death. Texas Drought 1. Roots that are without water for extended periods of time will die. New roots hairs will not be made in constantly dry soil. 2. Trees can deal with extreme drought by closing their leaf holes to save water. They will then use their stored food reserves to stay alive. Texas Wind and Humidity 1. Wind is bad in that it forces the closing of the leaf holes to prevent drying out. This limits their cooling effect and carbon intake which slowly weakens them. Photosynthesis can stop after 4 days of strong hot winds and then is difficult to get it restarted, especially under less than ideal conditions. 2. Humidity is good for trees as they will dry out slower. Sudden Texas Weather Changes 1. Trees constantly monitor their conditions and make adjustments but sudden changes in temperatures, wind, humidity, or water levels will occur much faster in Texas than trees can adjust too. It is beneficial to adjust your irrigation to help your tree adjust to sudden changes in weather. Trees will adjust to cold better if they are not too dry. Trees will adjust to sudden increases in temperatures or wind when watered soon after the weather change. Sometimes Texas can be very wet for several weeks then suddenly hot and dry but your tree may need additional water to help it adjust to its new conditions. Maples adapt faster than almost all trees but the Texas weather can change even faster. Solutions 1. Consistent deep watering is the best plan to deal with heat. Once a week watering should be enough. In extreme drought and hot conditions make sure that the whole root system is watered. On any established mature tree the root system extends past the drip line. 2. Use caution with fertilizers when temperatures are consistently out of the ideal range and do not apply to a damaged or heat stressed tree. Trees with heat stroke should not be fertilized until after full leaf expansion the following spring.. |
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