Ever since the early days of the landscape business, it has been known that some species of shade and flowering trees are easy to transplant in the fall, whereas others are extremely difficult or even impossible to get to survive. The difficult species are successful if they were dug the previous spring and held over the summer or if they were grown in containers during the previous summer as we are now doing on a much larger scale. However, even if they are dug “B&B” for immediate fall moving, survival is a very chancy affair. Just why some species of trees are safe to move in the fall while others, which appear to be quite similar, are very difficult remains an intriguing question, which has never been the subject of serious research or received a definite answer.  There will probably never be a single reason for fall losses of all difficult shade trees, but rather several reasons that apply to different species or groups of species with similar characteristics. The most important of these causes are detailed as follows.  1. Evergreen Foliage:  Broadleaf evergreens in general are notoriously difficult to transplant in the fall because if they have not rooted fast into their new location they can rapidly desiccate during cold windy periods in the winter. The same problems apply to broadleaf evergreen trees, especially in the northerly portions of their hardiness zones. Examples are: Ilex opaca, aquifolium, pendunculosa, etc.; Magnolia grandiflora.  2. Thin Barked Trees With Abundant Twigs:  These trees are especially prone to water loss in winter months, particularly when the ground is frozen and there are high winds. Just as laundry will rapidly dry on a windy, sub-zero day, even though it freezes solid when first hung out, so trees of this group dry out beyond the survival point even when they have no leaves. Thin bark is a very poor moisture barrier and abundant twigs, like abundant foliage, also make heavy drains upon the trees’ internal moisture supplies. Trees with abundant twigs are usually those with very small leaves such as Willow Oaks and birches. In contrast, trees with large, compound leave like Fraxinus, Gleditsia, and Gymnocladus have relatively fewer branches and are safe to transplant in the fall. Problem trees are: Quercus phellos (really difficult); Betula alba and papyrifera, etc.; Salix babylonica.  3. Trees With Coarse Roots Which Regenerate Slowly:  Here the problem is that, especially in B&B trees, the trees do not have enough roots to replace water loss during the cold dry periods during the winter. To compound the problem, trees included in the group have roots that are very slow to heal and push out new branch roots whenever they are severed. Research done at Rutgers University on the quite closely related Scarlet and Pin Oaks (both in the black oak section of the genus) showed that severed Scarlet Oak roots required three to four times more time to regenerate than Pin Oak roots needed to heal the cuts and thrust out new branch roots. The ideal time to dig and transplant trees of this type is just as they are breaking dormancy in the spring. At that point there is no large crown of foliage to support and the approaching flush of growth makes healing a much more rapid process than in the fall when the growth process are slowing down with the approach of dormancy. If transplanting cannot be accomplished at this ideal period because of construction delays, trees of this class benefit from being pre-dug at the best period and then being carefully maintained above ground as we do in our wholesale yards. The new mechanical balling machine methods with tightly fitting wire baskets encasing the root balls are especially well adapted to pre-digging for late season planting because the wires securing the balls do not rot as does rope. Examples are: Quercus coccinea, rubra and velutina; Nyssa sylvatica.  4. Trees Which Harden Up Late In The Fall:  There are a few species which grow late in the summer and which harden up very late in the fall. They retain their leaves very late and the abscission layer, which causes the leaves to drop, is especially tardy in developing. Thus, while early ripening trees like Fraxinus pennsylvanica can be dug quite early and will quickly ripen and drop their leaves, late ripeners like the Bradford Callery Pear dug at the same time will promptly dry up without dropping a single leaf. Then it is absolutely necessary to transplant late ripening trees in this group in the fall, it is essential to dig them as late as possible. The later they are dug in the fall or early winter, the better the chance of survival. Severe pruning at transplanting time, whenever possible, is also helpful in improving survival. Examples are: Pyrus calleryana Bradford, Aristocrat, etc.; Liquidambar styraciflua; Prunus subhirtella pendula, etc.; Prunus serrulata varieties; Prunus cerasifera varieties; Crataegus species; Tilia tomentosa; Quercus robur and fastigiata.  Of course deadlines for landscape planting jobs cannot always wait for ideal planting items. Losses can be minimized by changing varieties from hazardous to safe species of trees, digging the risky ones with larger than normal earth balls, and by planting trees re-established in containers. Thinning out or cutting back tree crowns and wrapping the trunks with tree wrap paper also help to reduce winter drying and losses on the planting site.

Courtesy of Bill Flemer III, Princeton Nurseries