Pruning branches is an essential part of horticulture but what about pruning tree roots? While trees are still saplings this is an easy procedure but once the tree takes root it can be a tricky process as pruning the roots can loosen the anchor your tree has or it can cut off the tree’s water supply. Despite this, sometimes it is needed if tree roots have spread out into your lawn or it has filled the container. To make sure you don’t kill your tree, there are a few simple things to take into account; the size and location of the root, the time of the year and how much of the root system you should cut.
To start with, trimming roots on transplant trees or saplings that haven’t taken root isn’t a problem, it just has to be done in a certain way. This is best to do before a sapling takes root as it becomes much more difficult once it does but this can all be prevented through methods that don’t take any effort at all beyond buying certain pots. Roots tend to not grow above ground because they are sensitive to light and air so by utilizing these mechanisms, the tree will prune itself. To air prune, buying fabric pots will allow the roots to grow and pass through the fabric wall but as soon as the root pokes beyond the fabric, it will stop growing. The same goes for light pruning which uses white grow bags instead of black lined pots. The white bag allows light through it so that any root that grows to the edge of the bag will stop as soon as the light hits them.
While these are good methods, sometimes the roots grow too large for the container and you will need to prune it by hand. To do this you first need to determine if your plant is root bound. If it is then this needs to be done but should only be done every two or three years as it causes shock and can kill the tree. The first step is to turn the plant upside down and remove it from the pot without using too much force. If it is stuck, simply use a knife to ease tension in the pot until it comes out. Next, using pruning shears you need to cut out the out bit of root and soil and prune the feeder roots, not any corm, bulb or taproot. If it is especially bad it can be good to prune the interior feeder roots but you need to be especially careful doing this. You also only want to prune, at most, two thirds of the roots but unless it is especially bad, shouldn’t be that much. Then simply repot with new soil and nutrients. This can be very traumatic to the plant so keeping it out of direct sunlight and watering it regularly is needed to help with the recovery process.
If it is a larger tree, this can be even trickier and needs a completely new set of rules to follow. This should only be done in early spring or winter as this is the time when it either isn’t growing, or is just starting growth again and won’t stunt the trees seasonal growth. You also shouldn’t cut any roots that are over two inches in diameter as removing large tree roots can cause the tree to become unstable or stunt its growth later on. You should also never touch any roots that are part of the trunk because these can cause huge structural damage that the tree will not recover from in most cases. On top of this, you should never cut more than 20% of above ground tree roots and like before, should only be done every two or three years. You should also never cut tree roots for aesthetic reasons, only if it is damaging a nearby structure or competing with grass or other plants. The best option is to ask a local arborist or horticulturist who is experienced in dealing with tree roots to prune it for you. Despite this, tree root pruning is always going to be detrimental to the tree and will always have a chance of killing or stunting the tree permanently. It should be the last thing that you try but if you feel you have to, it is always best to ask a local professional first.
If you do want to do it yourself, you should follow these steps and hope for the best as there are no guarantees in this procedure. First, you need to find the trouble root and follow it to the tree in question, making sure that it is not a larger root which you would need to consult with a professional about cutting. If it is a smaller root, measure the trees diameter about four feet from the base of the trunk and divide that number by pi. Usually, you can trim smaller roots that are at least three to five times the diameter of the trees length away from the base so if the diameter of your tree is 5 feet, don’t cut anything closer than 15-25 feet away. Next, cut a hole around the offending root and remove all the soil to expose it to the air, enough that you can get a saw into the hole to cut the root. Lastly, just saw the root so you can pull the cut off end of the root away from the tree and replace the hole and any disturbed area with the same soil. After doing this, it is important to keep a close eye on the tree as any sign of problems with the tree needs an arborists attention as soon as possible.
While doing pruning roots yourself can be rewarding and cost effective, it is always a good idea to have a professional do this procedure instead of attempting it yourself if you are unsure of your ability. If you do feel the need to do it, it is important to be extremely careful and if you are unsure at any point, ask questions of professionals as there is a high chance of messing up and killing the tree.