Growth and water relations of Kentucky coffee tree [Gymnocladus dioica
(L.) K. Koch] whips in translucent tubelike shelters were investigate
d. In a container study, 1.2-m-high shelters were placed over whips fo
llowing transplanting, then diurnal microclimate, water relations, and
water use were measured. Shelter air temperature and vapor pressure w
ere substantially higher, and solar radiation was 70% lower, than ambi
ent conditions. Sheltered trees responded with nearly three-times high
er stomatal conductance than nonsheltered trees. However, due to subst
antially lower boundary layer conductance created by the shelter, norm
alized water use was 40% lower. In a second experiment, same-sized she
lters were placed on whips following spring transplanting in the field
. Predawn and midday leaf water potentials and midday stomatal conduct
ance (g(s)) were monitored periodically through the season, and growth
was measured in late summer. Midday g(s) was also much higher in fiel
d-grown trees with shelters than in those without. Sheltered trees in
the field had four times greater terminal shoot elongation but 40% les
s stem diameter growth. Attenuated radiation in the shelters and lower
specific leaf area of sheltered trees indicated shade acclimation. Sh
elters can improve height and reduce water loss during establishment i
n a field nursery, but they do not allow for sufficient trunk growth.