Dipping bare root trees
in hydrogel at the nursery
right after harvest affords
more storage time before
fine oots desiccate
and has been shown to
improve transplanting
success over trees whose
roots were not dipped in
hydrogel. Bassuk speaks
about this research in
her Tree Fund webinar.
Photo Courtesy UHI
How does studying water uptake add to the conver-
sation around fall planting? "There's this pervasive
idea that certain species are inherently fall trans-
planting hazards," Bassuk says. "Nurseries post lists of
"fall hazards," but these lists don't take into account
variables like tree production method, handling of
fall-harvested trees, tree caliper size, and care of the
trees after planting. We can also ask, how many of
the species on 'Fall Hazard' lists fail because they are
prone to cavitation and drought stress regardless of
production method, and what can we do to over-
come that? In our quest for tree biodiversity, we don't
want to rule out a long list of species that could, with
due consideration, be successfully planted in fall."
In a June 2021 Tree Fund webinar, Why Do Some Trees
Transplant Better Than Others? A Look at Some New
Research on Water Uptake, Bassuk first lays out the
advantages and disadvantages of the three main pro-
duction methods, then presents on several extended
research studies that have implications for trans-
planting success and for the notion of "fall hazards."
The studies measure shoot extension, leaf area, and
hydraulic conductivity—three important indicators of
successful establishment of trees. The latter is mea-
sured by a hydraulic conductance flow meter.
In the early 2010s, Bassuk and team transplanted con-
tainerized 2.5 inch (64 mm) caliper swamp white oak
(Quercus bicolor, a famously easy to transplant oak) and
bur oak (Q. macrocarpa, a notably difficult to trans-
plant oak) in spring and fall. They measured hydraulic
conductance of the fine roots before, and six months
after, transplanting to see how well water was moving
through the xylem. Both spring and fall transplanted Q.
bicolor showed robust hydraulic conductance, but Q.
macrocarpa's water uptake declined significantly after
six months, regardless of season. These findings cor-
respond with field observations by Bassuk and urban
foresters of the extreme ease (Q. bicolor) or difficulty
(Q. macrocarpa) of transplanting these two species.
In a subsequent study, Bassuk and team experi-
mented with small (3 gallon/11.4 liter) and large (10
gallon/38.9 liter) containerized Q. bicolor and Q. mac-
rocarpa trees. Because pot-bound circling roots can
be a disadvantage of the container growing method,
the team introduced root pruning to compare with
non-root-pruned controls. They found that, with
root pruning, the 3-gallon trees showed a significant
increase in water uptake, while the 10-gallon trees
did not. This finding speaks to the observed ability
of smaller trees to regenerate roots more readily
than larger trees, take up water more readily, and
therefore better establish after transplanting. It also
speaks to the benefit of root pruning (please see Dr.
Bassuk's Tree Fund lecture for details about the spe-
cific root pruning technique used in this study.) >>
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