We have all heard that some trees cannot be dug in the fall right? So which trees and why not? Seems like everyone has a different opinion. Yet there seems to be very little actual research and or concrete data. Here at Ruppert Nurseries we have been studying the issue for several years and have reached out to many of our fellow growers and other professionals for input. Here are my thoughts on why some trees are more difficult than others to transplant in the fall.
Some evergreens can struggle with fall planting if they have not completely “re-rooted” into new locations. This lack of new and establishing roots can cause the evergreens to desiccate quickly during cold windy winter periods. A time when very little watering is thought to be needed. Ilex opaca and Magnolia grandiflora are example of evergreens which can have problems.
Thin barked and very “twiggy” trees can also suffer a similar problem when transplanted in the fall. Thin bark does not do a good job of retaining moisture and abundant twigs will allow trees to dry out quickly. So like the evergreens, slow to re-generate root systems, in cold winter soil temperatures do not keep up with the rapid loss of moisture. Quercus phellos and Salix babylonica are examples of trees that fall into this category.
Trees with very coarse root systems also are very slow to regenerate and establish new roots. So when these trees are harvested in the fall (especially late fall) they simply do not have enough of a root system to keep up with the water needs of the tree. Quercus velutina and Nyssa sylvatica are examples of coarsely rooted trees.
We can even see substantial differences on seemingly similar trees whose root systems do not regenerate roots at the same rate. Studies have shown that the root system of Quercus palustris (Pin Oak) regenerated roots 3-4 times faster than Quercus coccinea (Scarlet oaks). This along with the fact that Pin Oak have a fibrous root systems explain why the Pin Oak is not a fall dig hazard and Scarlet oak is a fall dig hazard.
So if we know the “why” about fall digging hazards what can we do to minimize the risk when job site limitations demand fall digging? Here are several steps we have found to improve survivability.
1.) When possible substitute for a tree which does not fall into one of the above categories.
2.) Have the tree root-pruned during the spring or summer which will allow new root generation prior to the actual transplanting.
3.) Over-size the root ball. This brings more of the root system with the tree which combats many some of the issues.
4.) Use anti-desiccants to slow the loss of moisture from winter winds.
5.) Increase watering before the trees are dug and after planting through the winter months when possible.
As with most things, there is rarely a simple or even a single answer to problems with many components. There are many factors which impact all tree digging and site survival of trees. Many thoughts and ideas have changed over time. 30 years ago I would have never thought deciduous trees would have been summer dug at the rate and with the high success we have today. I am sure many of you that have planted some of these trees in the fall with great success as I have. However time and experience has shown us that these factors do impact survivability. Some jobs and customers leave us few options, but hopefully our experiences with fall digging hazards will help your jobs be more successful. Some of the information above was shared by Bill Flemer III of the former Princeton Nurseries one of the great nurserymen of our industry.
Written by Kelly Lewis