Healthy Trees Part 2 – Root Systems

The most important part of a healthy tree is its root system.  If the roots aren’t happy, there is nothing you can do for the rest of the tree.

Most problems with root systems are related to poorly drained or overwatered soils.  Improper planting, maintenance issues, extreme weather conditions, and environmental situations then contribute to the trees decline.  Root diseases usually get started beause of one or more of these problems, then the tree goes into decline, and finally pests or weather conditions will finally kill the tree.

Signs of an Unhealthy Root System –

• Dieback of the crown, a section of the top, or main limbs
• Rounding of the crown (terminal growth has slowed) mainly in evergreens.  Stunting or poor growth may also be evident.
• Cone production on evergreen tree increases dramatically but smaller in size and of poor quality.
• Leaf or needle color is dull or starting to yellow.  With hardwoods, fall color may show up early, especially on a limb or section of the tree.  Early leaf drop.
• Thinning of leaves on deciduous trees.  Leaf size may be reduced.  With evergreens, older needles drop off early leaving only 1 or 2 years of growth, contrary to 3-4 years of growth on healthy trees.
• Discolored wood at the base of the trunk.

  

• White fan-shaped mold or dark brown shoestring-like threads (rhizomorphs) under bark near base of on roots.  Possibly honey-colored mushrooms growing at the base of the trunk.
• Evergreen trees turn uniformly reddish-brown suddenly, specifically if bark beetles are not evident.
• Root diseases can grow up from the root system to the inner bark causing cankers or sunken dead areas.

Root Diseases –

Though there are many diseases that cause root rot, only a few stand out to be the most prevalent.  Many of the other diseases act similarly, and the results and recommendations are usually the same.  These most common root diseases are:

Armillaria Root Rot – best identified by signs of mushrooms or white patches of fungal growth at the base of the tree.  If bark is loose, dark brown thread-like strands will be visible, known as rhizomorphs.  Watch for signs of decline.

Phytophthora – Leaves appear to be drought stressed, discolored or dull.  A red-brown color on the wood underneath the bark near the ground can be seen. Fungal patches are not visible with this disease.

 

Solutions for Root Diseases –

Essentially, there is no cure for these common root diseases.  The fungus stays in the soil for years and will infect future plantings until the conditions causing the problem are changed.  They will attack trees of any species and any size.  Only a healthy tree can resist these diseases, and that includes proper planting, care, and maintenance.

Once disease is detected and conditions remain unchanged, it will only be a matter of time before the tree dies.  The problem must be corrected before planting the same type of tree back in the same spot.

A few chemicals may slow down the progress of root diseases but should be used only by an arborist.

Steps to Prevent Root Diseases –

Only a healthy tree can resist fungal attack.  In order to keep a tree as healthy as possible, follow these practices:

• Proper planting of the tree, ensuring good drainage and that the root flare is at or slightly higher than ground level.  Thorough watering on a weekly schedule for the first year will reduce stress while the root system is becoming established.
• Raise the planting site or create a drainage channel to improve drainage.
• Remove soil if it has been piled up over the root ball.  The root flare must be visible.
• Proper watering during dry spells or droughts, even in winter.
• Apply and maintain a layer of mulch over the root system will reduce moisture stress.  Keep mulch away from the trunk at all times.
• Avoid wounding the tree.  If a tree is using valuable energy to heal excessive or damaging pruning cuts, lawn mower or weed eater damage to the trunk, or environmental causes affecting the bark, any of these can stress the tree to the point that it becomes more susceptible to root diseases.
• Watch for changes in soil drainage that allows for water to pool in the root zone area.  Avoid planting near drain spouts.
• Avoid excavation or soil compaction in the root zone area.  Keep in mind that roots grow much further from the trunk than expected, definitely well beyond the branches.

Resilient Trees for Replacement –

The Missouri Dept of Conservation recommends these native trees as resistant to Armillaria Root Rot and possibly other root diseases:

• American Sweet Gum
• Bald Cypress
• Black Cherry
• Cucumber Magnolia
• Hackberry
• Kentucky Coffee Tree
• Pawpaw
• Pecan
• Sycamore
• Thornless Honeylocust
• Tulip Tree (yellow poplar)

Surface and Exposed Roots –

Some trees tend to have a shallow root system.  In some cases, the soil may have eroded away from older roots.  As long as the tree is not suffering from poorly drained or standing water, the bulk of it’s root system will sufficiently support the tree.

However, just like the bark of the tree, roots that are damaged from mowers, sunscald, or vehicle/pedestrian traffic can be susceptible to bacteria, fungus, and insects entering the tree.  Care should be taken to protect exposed roots through mulching or planting a ground cover that does not need to be mowed.