Tree roots actually live on the top 10-15 inches of the soil so they can access oxygen and water. They do not go deep into the soil. This graphic shows how tree roots spread. The feeder roots are found at and beyond the drip line (the area outside the canopy).
You can still help save your tree by removing the excess mulch from the base of the tree. Having mulch around the base of the tree is like you trying to live with a pillow over your face. Not easy! You need to remove the mulch until you see the flare at the base of the tree. You will probably encounter small sucker roots in the mulch. These sucker roots have been generated by the tree to try and get some oxygen to breathe. Trim the roots out. Removing them will not hurt the tree if you remove the mulch at the same time.
Mulch can be beneficial for a tree. Research has shown that trees grown in a proper mulch bed will grow twice as fast and be twice as healthy as trees grown in grass. Grass sends out a chemical to kill tree roots, so placing a wide mulch bed around your tree will help the tree. Make sure the mulch is no deeper than 2-3 inches and at least 3-6 inches away from the flare of the tree. If possible, the mulch should go all the way out to the drip line of the tree, where the feeder roots of the tree are found. Here is a picture of a perfect mulch bed around a tree.
You are only required to remove the excess mulch from the city owned trees (those located between the sidewalk and the curb). Going forward you are required to reapply the mulch correctly. We encourage all residents to do the same for the trees and shrubs in your yard. Landscaping is a big investment and this will save you money in the long run because your trees and shrubs will live longer and be healthier.
We attend many tree conferences over the years, and mulch volcanoes are always discussed as a huge problem. The consensus is – over-mulching kills trees. Tree Fredericksburg and the City are here to give professional unbiased advice that is best for your trees.
Trees do take in carbon dioxide through their leaves (photosynthesis), but trees also take in oxygen through their roots. All living things need oxygen. The flare of the tree is located at the base of the trunk and looks like this photo. The flare is often referred to as the lungs of the tree. If the tree is planted too deep or mulch is pile up around the base of the tree, then the tree is not able to take in enough oxygen. We need to keep mulch completely off of the tree flare.
The tree will grow slowly, and eventually decline and die. Without oxygen, the tree is stressed and insects can invade the bark and eventually kill the tree. Trees that do not have enough oxygen also have branches that die back and the crown of the tree will be sparse. Here are two pictures from the same neighborhood. Both are maples, and were planted at the same time. One had mulch piled up around the base and one did not. Can you guess which one had the mulch volcano?
The City of Fredericksburg guidelines for mulching require pine bark mini nuggets to be used. The mini nuggets do not break down as fast as shredded hardwood mulch and allow oxygen and moisture to reach the tree roots. Shredded hardwood mulch forms a thick mat and repels water and can smother your tree and deprive the tree of water. Shredded hardwood also leaches magnesium out of the soil and this prevents trees and plants from being able to uptake iron from the soil causing disease and decline in the trees. With pine bark nugget you should only have to apply fresh mulch every 3-5 years. If you want fresh mulch you can remove the old mulch and put down new mulch, or you can spray the mulch with vegetable dye to recolor it every year.
The practice of over mulching is driven by a number of factors. Some thought it “pretty” and started to apply mulch this way. Others followed because they saw commercial landscapers applying mulch this way and thought it was the correct way. Many quality landscapers now know they are damaging the trees and shrubs but homeowners still insist on having it done this way because they see it done at commercial establishments.
Don’t plant your trees and shrubs too deep, you will smother them. Place the flare at soil level. During dry periods water slowly along the drip line and don’t overwater – plants can drown.
Don’t Smother your Trees this Spring – Learn How to Properly Mulch Your Trees!
⇒ Mulch: Mulch must not exceed 3 inches in depth and must be a minimum of 4 feet diameter around the bases. Too much mulch can be deadly to trees!
⇒ Edging: Edging must not exceed 1 inch depth around mulch beds.
⇒ Soil: After planting, do not add any extra soil on top of root balls or tree roots.
For much more mulch information, read the Fredericksburg Department of Public Works’ Mulch Standards Fact Sheet