What are Tree Berms For?
A berm is a sort of basin constructed of soil or mulch. It serves to keep water in the right place to drip down to the tree’s roots. Planting trees on berms makes it easier for the trees to get the water they need. If you are wondering how to make a berm, it isn’t difficult. To build a berm, you construct a circular wall of soil that goes all around the tree trunk. Don’t put it too close to the tree, or only the inside of the root ball will get water. Instead, build the berm at least 12 inches (31 cm.) from the trunk. How to make a berm wide enough? Use soil or mulch to construct the wall. Make it about 3 or 4 inches (8-10 cm.) high and twice that wide.
Do Trees Need Berms?
Lots of trees grow perfectly well in fields and forests without berms, and most trees in the backyard may not have berms either. Any tree that is easy to irrigate may do just as well without a berm. Planting trees on berms is a good idea though when the trees are isolated on the far corner of your property or located somewhere that is difficult to irrigate. Trees in remote locations require the same amount of water they would if planted nearby. Berms are great for trees on flat land you intend to water with a hose. All you have to do is fill up the basin and allow the water to drip slowly down to the tree roots. If you have a tree on a hill, create a berm in a semi-circle on the downhill side of the tree to stop rainwater from flowing away.
When to Build a Berm
In theory, you can build a berm around a tree whenever you think of doing it and have the time. Practically, it’s a lot easier to get it done at the same time you plant the tree. Building a berm is easy when you are planting a tree. For one thing, you have lots of loose soil to work with. For another, you want to be sure that berm construction doesn’t pile extra soil on top of the root ball. This can make it more difficult for nutrients and water to sink through to the roots. The berm should start at the outer edge of the root ball. This too is easier to gage at planting time. Also, the period the tree will need extra water starts at the time of planting.
