growing plants around a gum tree

Question

My partner wants to grow plants (agapanthus) around the base of our very old 80ft tall gum tree. He has dug down about half a foot and out about 2 foot and wants to build the soil up around the base of the tree and put in an edge of rocks. Will this cause any damage, such as rot, to the base of the gum tree?

Answer 1

Yes, building up soil around the base of an established tree can cause issues, ranging from crown rot (where the bark rots around the top of the roots) to suffocation of the root system. I would not recommend adding any more than 2 additional inches of soil over the roots of an established tree. It sounds like he has dug down and may have done some root damage to the upper root system of the tree in the process. But he may not have. Just keep an eye on the tree and give it some phosphorous for good measure. Instead of building up the soil, a better solution might be to build a series of containers or a contained bed around the tree that will keep the soil from touching the trunk and would limit the spread of the additional soil to a small area so that the risk of root suffocation is reduced.