urban-forestry.com 39
Dave goes on to explain the other characteristics of
Compton oak that can be intermediate and variable,
such as leaf shape. He says, "Q. lyrata has rather dra-
matic lobes and sinuses, while Q. virginiana has its
basic oval or paddle shape leaf. The offspring can exist
anywhere along the continuum. Then there's growth
habit. Q. lyrata is an upright, apically dominant species,
while Q. virginiana is anything but. The offspring, once
again, express traits in a range between the two."
Dave and colleagues observe interesting correlations
in the field. "Most of the deciduous expressions of
Compton oak are also upright in habit and have leaves
more reminiscent of Q. lyrata. On the other hand, the
semi-evergreen ones tend to have the wide-spreading
growth habit of Q. virginiana, along with simpler leaves."
Tolerance of alkaline soil also expresses along a con-
tinuum. "As with virtually all of the deciduous oaks
of the southeastern United States, we see some
chlorosis on Q. lyrata in California, whereas I don't
think I've ever seen chlorosis on any of the thou-
sands of Q. virginiana I've seen in the state," Dave
says. "So far we haven't seen chlorosis on any of the
Compton oaks I've seen in the landscape. And the
types closer to Q. virginiana predictably will have
somewhat better tolerance for alkalinity, while the
types closer to Q. lyrata show less tolerance."
Dave has observed that soil moisture comes into play
with tolerance to high pH. "I suspect that if you try
to plant Q. × comptoniae in California with a strong
Q. lyrata component, and the site is really dry/com-
pacted, you will likely see some chlorosis," he says.
"However, if grown on alluvial sites throughout
most of the state, any of the types will thrive."
Compton oak is starting to come into nursery production
and street tree use in hot, dry climates such as that of
Visalia, California in the Central Valley. ("For nursery pro-
duction in California, we tend to cull the semi-evergreen
ones, and keep the upright deciduous types," he says.)
Dave works with nurseries in the state to
encourage production of Compton oak, and he
advises private arborists, municipalities, and insti-
tutions on planting these trees on a trial basis.
He then collaborates with these partners to
monitor how these trees do in the urban environ-
ment in the short, medium, and long term. >>
Compton oak elevated for clearance. Compton oak trunk.
