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www.arborage.com ARBOR AGE FALL 2015 13 INDUSTRY INSIGHTS PHOTO BY MATTHEW STEPHENS in parentheses — include tulip tree (Liriodendron tulipifera) (Erb found it needs to be transplanted earlier in the fall), black gum (Nyssa sylvatica) (similar survival rate to spring-planted trees), and Kentucky coffeetree (Gymnocladus dioicus) (when transplanted at 2- to 2.5-inch caliper). On the other side of the ledger, Tree Pittsburgh has tried fall planting of river birch (Betula nigra), flowering cherry (Prunus spp.), goldenrain tree (Koelreuteria paniculata), and sweetgum (Liquidambar styraciflua) — but has had mostly failures with those species. Hence, these are some of the few species they avoid planting in the fall. Upper Arlington, Ohio, Superintendent of Parks and Forestry, Steve Cothrel, has learned to give credence to his local nursery's advice in light of when his fall planting program takes place. Cothrel said that his fall B&B trees are typically dug and shipped in October. "Digging stock of certain species later in the fall — when plants are more fully dormant — might help with the 'fall hazards' from what I've heard," he said. "But that would not work with our installation schedule. It's all we can do as it is to get trees planted before serious winter arrives." Based on this installation schedule and his many years of observation, Cothrel avoids fall planting of oaks (except swamp white oak), magnolias (Magnolia spp.) (including tulip tree), river birch, black gum, beeches (Fagus spp.), hawthorns (Crataegus spp.), horsechestnut (Aesculus spp.), and baldcypress (Taxodium distichum). However, he says that he has observed no readily apparent survival differential between fall- and spring-planted 1.5-inch- caliper trees that some consider touchy in the fall, including lindens (Tilia spp.), zelkova (Zelkova serrata), goldenraintree, callery pear (Pyrus calleryana), and elms (Ulmus spp). FIVE BRANCHES OF TRANSPLANTING SUCCESS In her work in her home city of Ithaca, N.Y., and with dozens of other municipalities, Bassuk has found that for bare root trees under 2-inch caliper, it has been easy to successfully fall- transplant many of the trees frequently appearing on fall hazard lists — including London planetrees, goldenraintrees, crabapples (Malus spp.), zelkovas, cherry trees, pear trees, oaks, and elms. This tells us that season plus species isn't the only key interaction in the fall hazard picture; production method comes into play as well. Bassuk said that the five major interacting factors influencing transplanting success are season, species, production method, size and aftercare. Season is best understood in its interactions with the other factors, while the essential nature of good aftercare (watering, weeding, mulching, avoiding damage to bark, etc.) is obvious. Species: Bassuk and colleagues are currently investigating why some tree species are more difficult to transplant than others. It has to do with the ability of a given species to maintain hydraulic conductivity by avoiding cavitation (obstructing bubbles in the xylem) after its roots are severed. Why is bur oak (Q. macrocarpa) so difficult to transplant while its close relative, swamp white oak, is relatively easy? Said Bassuk, "Our early results show that bur oak isn't able to These hedge maples (Acer campestre) were dug too early.