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How have you used root pruning?

For those not familiar with it, root pruning is when roots are reduced to encourage new root growth and/or to create a clean cut in what would otherwise be a mangling of the roots due to trenching or some other random destructive root practice. We are curious when, how, and why you have root pruned?  What type of tools have you used and what sort of preparation is necessary? Have you root pruned a large tree?

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  • Yes, don't buy a pig in a poke, as they say; find the flare!

    I found this on the web.  It's the last chapter in a book that's full of good research.  Also check the new ANSI A300 Part 8 root management standard, hot off the presses!.

  • That was some good perspective, Brian. I agree that it starts in the greenhouse and takes effort. Some people just start them in one pot and walk away for a few years. Thanks for sharing.

  • Sorry I'm joining this conversation a little late, but does anyone have any thoughts on grow bag trees.  First off, I'm not trying to pitch a certain product or sell trees but we are trying to find the best ways to grow trees and eliminate the circling problem.  We are a small nursery in Nebraska and after two years of growing in smooth sided containers we started looking for a better system.  We have found that going through the Rootmaker system and ending in either their RootTrapper bag or knit fabric in-ground containers, there is little work at planting time and the trees seem to establish quickly.

    We have found that it all starts in the greenhouse with seed that we collect locally to our area and germinate in air root pruning trays.  We then shift the tree twice and end in either a 7 or 15 gal bag that then uses constriction of the roots to create a more fibrous root system with very little if any circling.  When it comes time to plant in the landscape you simply roll the bag off or make a few cuts in the bag and tear off. Does anyone have any thoughts on pruning containers as a way to combat the circling problem?  As a young nursery we are always looking to improve our growing method and any suggestions form the industry/tree planters are always welcomed. 

  • Arlington county considers it to be some relief for construction damage to roots, where limits of disturbance go within the critical root zone. It's not always appropriate, so it's very hard to create legislation around root pruning. It's perhaps used too liberally, and people think it removes their liability, which it merely reduces. I'm learning more about the impacts of root pruning, and some trees take it better than others.
  • GREAT INFO!  Thanks Kevin, Lawrence, James, and Scott!

  • Root pruning is a really good tool for very young trees to increase RGP (root growth potential.) If done properly it allows exponential growth of roots which in turn gets the root-shoot ratios more to appropriate levels.  Once the roots are pruned, the lateral, secondary and fiberous roots really take off and grow.  If you take care of the roots, the tops or shoots will be fine.  We like to prune in late Fall, when they are not under a lot of stress.  And yes, a sharp, clean cut is recommended.      

  • It is almost a requirement for container trees, as pointed out above. Improves survivability and growth for pot-bound and root girdling trees.

    For old trees on construction sites, it may be lesser of two evils. Clean pruning with air spade or by hand in the trench may be necessary.Better than mangled roots from bulldozers and excavators.

  • Root pruning is most always needed when you have purchased container grown plants. Usually the plants have been left in the containers for far too long and have numerous circling and crossing roots. To remedy these you can use seceteurs and hand saws.

    I have root pruned many large trees over the past fourty some years using handsaws and also stump grinders.When using stump grinders be sure the cuts are clean, not ripped and torn. Many times to keep the roots contained in certain areas such as away from sidewalks,driveways etc. it is necessary to prune them.


  • Neil,

    I'm glad you shared the U of Florida information. We just had Dr. Gilman speak at our Northern Rockies Tree School Conference in Montana and he talked a little about roots and pruning prior to planting. What I took from his talk was that it is important to closely examine and assess the root ball first. We bought a small containerized tree from a local nursery and did a demonstration in front of the group.  When looking at the root ball he identified several places where it was apparent that the roots were beginning to circle, but nothing extreme. Gilman explained that the best action was to cut away the sides of the root ball to eliminate those circling roots, even though they were small. The end product looked basically like a root cube rather than a root ball. It was a good example, and I'm sure the tree would thrive after planting. 

    However, I have tried to root prune an arborvitae and dwarf spruce that had severe circling roots, and in just a few months the trees died. I fear the trees were already too stressed (bought at a box store - lesson learned!) and cutting at the roots made things worse.

    So after these couple of experiences, I think it comes back to inspecting for good quality stock at a reputable nursery. Even a tree with some circling roots might be ok if the nursery is caring for them and watering them enough. You get what you pay for!  

    Administrator said:

    Here is a great resource from University of Florida:

    Root pruning guidelines

    Trenching and digging in the soil near trees can cut roots, and this can damage the tree resulting in tree decline or the tree falling over (See: fallen tree from cutting roots). This can cause liability and safety concerns. Root pruning is more injurious to old mature trees than it is for younger more vigorous trees. Cutting roots greater than about one inch diameter during trenching and digging can mean problems for the tree. In some cases roots of one to three inches diameter represent the major structural roots holding the tree upright.  SEE MORE

  • Roots must be exposed using an air spade and then pruned using a hand saw or chain saw.  Of course many issues with root pruning potentially harming the health and stability.  I have seen recommended not removing roots within 3x-5x diameter of tree. One other source says 5-8 inches per DBH inch away from root collar. Structural roots are typically in tension during wind so one must give careful consideration to removal of any structural roots. Recovery can take years. Root pruning on container trees can be done much more generously and is recommended by root expert Ed Gilman of the University of Florida, particularly in removing girdling roots.  He has written several articles on how root pruning on container trees can increase long term health of tree as new roots grow quickly from where pruned as as the tree is young is not depending upon them too much for structure. 

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