Cultural Problems
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VOLCANO MULCH For some reason there has been a recent increase in the practice called volcano mulch. This is where mulch is piled up around the trunk of a tree. Some people like the way it looks, some people do not. Regardless of how you feel it looks, it is not good for trees. Before we talk about why volcano mulch is bad, let’s talk about proper mulching and its benefits. Much of this information is also available in the brochure “Proper Mulching Techniques” which is printed by the Trees Are Good division of the International Society of Arboriculture (ISA). This is a great source for information about tree care. Benefits of proper mulching: Holds in soil moisture. Evaporation is reduced, therefore reducing the need for watering. Helps keep weeds from germinating. Improves soil aeration, structure and drainage. Can inhibit certain plant diseases. Keeps power tools such as weed whackers and mowers away from trunk thereby avoiding damage. Properly maintained mulch can give beds a uniform, well cared for look.
THIS IS A PROPERLY MULCHED TREE Trees growing in a natural settings such as a forest preserve are growing in rich, well aerated soil full of nutrients. The soil is full of leaves and organic materials that recycle nutrients and provide an ideal environment for root growth and mineral uptake. This is the idea behind mulching trees with organic mulch such as wood chips or shredded bark. Problems with improper mulching: Piling mulch against trunk can hold in moisture and cause rotting. It can also lead to disease and insect problems. This can also create habitats for rodents that chew the bark and can girdle the trees. Too much mulch over the roots causes them to be buried too deep and deprives them of oxygen.
THIS IS THE WAY A TRUNK FLARE SHOULD LOOK Proper mulching: Do not place mulch against trunk. Never cover up the trunk flare (more on this later). Whenever possible, extend mulch out to drip line or beyond. This is the point where a line is drawn to the ground from the ends of the branches. We use the drip line as a guide for where the ends of the roots are even though they usually extend farther than this. The mulch should only be 2-4 inches thick, thinner if the drainage is poor. Don’t add mulch if there is a sufficient layer in place. Rake the old mulch to break up matted layers and refresh appearance. On every tree the trunk goes down to a point where the roots start and flares out. This is the trunk flare. Another problem that is quite common is when the trunk flare of a tree is not exposed. Sometimes this happens when a tree is planted too deep to begin with or soil or mulch is piled on after the tree is planted. The end result is the same, the trunk flare is buried which means the roots are too deep. This is one of the reasons for girdling roots. The best way to avoid this situation is to plant the tree properly to begin with; that is, with the trunk flare above the ground. If it’s too late for that you need to physically remove the excess soil/mulch to expose the trunk flare. This can be a lot of work so you might want to consider hiring a company that will use an air spade to excavate the trunk flare. The air spade removes the soil/mulch without damaging the root system.
THERE IS NO TRUNK FLARE SHOWING ON THIS TREE! OR IS IT A UTILITY POLE? THIS IS NOT GOOD! |
GIRDLING ROOTS  Girdling roots grow in a circular or spiral pattern. They may form in root bound container grown plants, begin when a tree is transplanted, or develop as a tree grows. Poor planting techniques, deep mulch, or compacted soil seem to encourage the development of girdling roots at the base of the trunk. Any tree can develop girdling roots but certain trees are more prone to this problem than others. The most common in Chicagoland is Maples, especially Red Maples, followed by Birches, Lindens, and Hawthorns. As roots circle the trunk, they can slow and eventually cut off the flow of sap in the tree. Carbohydrates produced by the leaves, through photosynthesis, are unable to move through the phloem to the roots. Weakened roots are unable to provide adequate water and nutrients to the leaves. Trees with girdling roots tend to decline over a 5-10 year period. Symptoms associated with girdling roots are caused by a weakened root system. The crown of the tree may be thin, with stunted growth. If you compare the tree crown to a clock, damage may first occur in the upper portion, between 10 and 12 o’clock. Leaves may be lighter green, scorched, show early fall color, and early leaf drop. Twig or large branch dieback can occur. When one side of the trunk is straight (flat), with no natural flare, this usually indicates a girdling root below the soil surface. Trees with severe girdling roots may lean or completely break off. Reduced sap flow makes the tree more susceptible to insects, disease and environmental stress. Once a tree reaches maturity, it is very hard to fix girdling roots. This involves excavating the root system and physically cutting the girdling roots. In most cases, this can do more harm than good. Mycorrhizae fungi treatments are used to help the tree to compensate for girdling roots. The mycorrhizae fungi will put on a secondary root system and allow the tree to more efficiently take in the nutrients in the soil. This allows the tree to live longer then it would if nothing was done. The best way to treat girdling roots is to avoid them in the first place with proper planting and cultural techniques.
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