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Diagnosing Root Death in Woody Ornamentals

Root Death is an important cause of poor plant health in woody plants. When roots are killed, the plant is not able to take up sufficient water or nutrients to support the development of branches, leaves, flowers, or fruit. Usually, the above-ground symptoms appear long after root death has been occurring. As a result, it is difficult to treat the plant so that it recovers fully. It is worth the effort to determine the reason roots were killed, particularly if the plant will be replaced. Although this can be a very difficult process, it is sometimes possible to identify the cause of root death by carefully observing signs of the problem. Below are some of the symptoms of root death, the signs that should be sought, and the questions that need to be answered in order to successfully diagnose the cause.

 


Symptoms Typically Occurring when Roots are Dead:

  1. Plant growth slows as compared to healthy plants.
  2. Leaves wilt or yellow and fall prematurely
  3. Margins of leaves die in the Summer
  4. Roots appear dark brown or black and few or no white roots or root tips can be found when the roots are washed free of soil. *NOTE* Some healthy plants (i.e. Azaleas, Rhododendron) naturally have dark colored roots.
  5. Roots are limp and not brittle and crisp as is found in healthy plants of all types.
  6. The plant has few small side branches or side branches are dead and only main branches are alive
  7. The canopy of the plant is very uneven because major branches are dead.
  8. During the Winter, there is an extensive cankering and dieback of small twigs and branches


Some of the Above Symptoms can be caused by:

  1. Root rotting fungi. Look for shelf-fungi, mushrooms, and 'deadman's fingers' growing on the butt, root flares, or main roots, particularly in late Summer and early Autumn. Fibrous roots may be black. A fungus may form a sheath, a white or black covering, just under the bark. The fungus may form dark brown shoestrings on or just under the bark. Or, the wood of the main roots and lower trunk may be black, black and resin soaked or brown to reddish brown. In elms, the wood just under the bark may be butterscotch-yellow and have the odor of oil of wintergreen. The wood of the root may be soft and decayed Apply ZeroTol Fungicide & Bactericide to prevent Fungus and Bacteria from forming on woody ornamentals.

  2. Over-fertilization. Be sure to determine what has been done around the plant over the years. A tissue analysis may indicate excessive chloride or toxicity problems.
  3. Flooding or drought. Check drainage patterns in the vicinity and any recent changes made in the drainage pattern.
  4. Root exposure to chilling or freezing temperatures or to excessive high temperatures.
  5. Toxicity due to insecticides, herbicides, and fungicides applied to the soil in the root zone. Damage from certain herbicides may become obvious 1 or 2 year after treatment.
  6. Girdling roots or ropes. Look for roots, ropes or wires encircling the trunk. If the trunk is abnormally flat on one side at the soil line, dig below the soil line to look for girdling root. Look for wires or ropes that were not removed at transplant but which now may be girdling the trunk.
  7. Planting or back filling too deeply. If there is no flare at the base of the tree it was planted too deep.
  8. J-rooting conifers. Excavating the root system will reveal that the main root is in a J-shape and is not growing downward properly.
  9. Roots were unable to penetrate the soil from the original transplant hole. Excavating the root system will reveal that the roots have not exited the original transplant hole significantly. The hole has acted like a flower pot possibly because; A) the equipment used to create the transplant hole compacted the wall of the hole, or (B) the soil is compacted or very difficult for the roots to penetrate clay soil.
  10. The plastic burlap material was not removed and roots were unable to exit into the surrounding soil.
  11. Insect feeding can kill root tips or girdle larger roots. Excavating the roots will reveal chewing or tunneling damage from various insects or the larvae of insects will be found on or in roots.

 


Before any action is taken, a diagnosis must be made of the actual cause of the symptoms. If the damage is due to the activity of fungi, fungicides are available which can check the fungus and allow the plant to grow. However, fungi are not completely killed by fungicides. Some spores will remain alive. Therefore, repeated applications of fungicides are necessary. ZeroTol Fungicide/Bactericide is a great preventative & curative measure. This organic product is very effective and safe for the environment, pets, and children.

 

Remove soil. If soil is piled up on the crown, carefully remove it to expose the root flare. Below is a picture of how a root flare should look.

How the Root Flare should Look
Rhododendron suffering from Root Rot
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