To Root Prune or Not to Root Prune? That Is the Question

Posted on: October 22, 2014

One of the most frequently asked questions at Ruppert Nurseries is, “How often do you root prune?”  This is a tricky question and one for which I wish there were a more clear cut (No pun intended!) answer. First; let’s dispel a myth.  Ready? Ok, here it is.. We do NOT root prune every tree in the nursery.  (Take a minute and digest that one, sit down if you need to).  Now that you are over the shock, I’ll tell you why we don’t.

Let’s talk for a moment about what exactly root pruning is.  Root pruning is just what it sounds like- it’s a pruning of the roots just as we would prune the branches only we do it with a tree spade, a shovel, or a trenching machine. Some of the reasons we might choose to root prune a tree are as follows:

  • A customer might need to have trees dug in a less than preferable season.  For example, oaks typically do not dig especially well at any other time than when they are dormant. But let’s say that the customer knows their job is not going until July.  We would then choose to root prune the trees during dormancy to help prepare the trees for digging outside of their optimal season.
  • Root pruning a tree will often slow down the growth of the tree.  I often like to say that trees are not multi-taskers. Most trees are only capable of doing one thing at a time.  They can either put out new roots or put out new leaves, but not both at the same time.  By severing their roots, it forces the tree to put energy into regeneration of new roots rather than primary and secondary growth (getting taller and putting on caliper).  And more roots are good, right?  RIGHT!
  • Because a root pruned tree will have a higher concentration of roots in a closer proximity to the trunk of the tree, we are often able to put a root pruned tree in a smaller root ball.  This turns into a win-win for many customers whose projects cannot accommodate a larger ball size or a large piece of equipment.  This ties in nicely to #2 above about purposefully slowing down the growth of a tree.
  • The benefits of root pruning are realized for more than just one season. A tree that was root pruned in 2013 will be more easily dug in an off season for likely 2-3 years beyond the date of the root pruning.

In a recent demonstration at Ruppert Nurseries, we root pruned a red maple in early spring.   We had actually root pruned it for a demonstration on bare-rooting that was rescheduled for a later date.  The preparation work we did for this demonstration however provided an excellent study in just how effective root pruning can be at creating new roots! In the photo below- you can see how many new fibrous roots were generated in about 4 months time.

Root Pruning Pic

Will you just look at those gorgeous roots!  You can’t have lustrous hair without a trim every now and again, the same may hold true for the roots of many species of trees!

We should circle back around to the original thought which was;  knowing what we do about the many great benefits that root pruning can realize, why would we not root prune each and every tree in our nursery?  If you remember, I mentioned that root pruning will often slow down the growth of a tree?  It certainly is a  great way to control growth in fast growing species such as Liriodendron (tulip poplar) and Prunus (cherries).  But what about Fagus (beech) or Gingko?  Slowing down these already slow growing species would result in longer than average growth times resulting in less trees available for sale.  Not really what we aim for in the nursery business.

The other truly honest reason for not root pruning is time,  or more specifically,  the lack thereof.  Root pruning is time consuming.  Each year we root prune (or plan to root prune) a certain number of trees so that we can extend our sales season throughout the less than desirable digging months of summer.  We mark these trees with a special color of ribbon and a silver tag with their root prune date on them so that we can track the history and progress of these trees.  Our plan is to increase the number of transplanted and root pruned trees so that we can offer more high value trees to our customers throughout the entire year instead of just a handful of ideal months.

As landscape professionals it is important for you to know when your projects will be installed so that we can prepare your trees months or perhaps years in advance.  Ruppert Nurseries is committed to making the best horticultural decisions possible with regard to proper digging and handling of trees.  We are happy to provide this service to you!


Written By Ronda Roemmelt