Through her ongoing UHI research, Nina
is looking forward to more time to pursue
her propagation-related research interests;
this has been an abiding passion since she
earned her doctorate from the University
of London in 1980 in Plant Propagation.
Readers may be familiar with
Nina's 25-year
hybrid oak propagation work, and some
readers even have UHI hybrid oaks planted
out for trialing in their communities.
"Out of the numerous hybrid oaks that
were developed in 2004-2006, we have
found about three or four particularly good
ones that we have started to propagate
via tissue culture," Nina says. "However,
the 'recipe' for success with these hybrids
tends to be genotype specific; each hybrid
needs slightly different conditions to mul-
tiply and root. Micropropagation of oaks
has never been consistently successful, but
after many years and the efforts of many
students and technicians, we're seeing
some light at the end of the tunnel."
Nina says she really enjoys the challenge of
working out techniques to propagate species
that aren't freely available in the trade
because people have found them so hard to
propagate. Like hickories, for instance. The
same process that she and her team devel-
oped for the hybrid oaks,
they're now applying
to hickories. "They have great potential for
urban use because they tolerate heat and
both wet and dry extremes, so they have
resilience to climate change," Nina says.
"They have food value for people and wild-
life, and they have beautiful fall color. But
right now, you can't get them in nurseries
because of the propagation barriers."
Nina and recent doctoral candidate Brandon
Miller have started with shagbark hickory
(Carya ovata), but once they "crack the code"
for that species, they want to apply what they
learn to propagating other useful and beautiful
hickories, like pignut hickory (C. glabra), mock-
ernut (C. tomentosa), bitternut (C. cordiformis),
true pecans (C. illinoinensis), and a species that
Nina in particularly fond of, shellbark hickory
(C. laciniosa), also known as kingnut. "Shellbark
hickory is such a beautiful tree, with sweet
nuts, shaggy bark, and the ability to tolerate
periodic flooding and drought," she says. "In
its native range, it's usually found in wetlands."
When Nina and Brandon used
layering, eti-
olation,
and rooting hormones to propagate
shagbark hickory by cuttings, they were
surprised and delighted that tweaking the
amount of IBA (indole-butyric acid) provoked
the plant to develop fibrous root systems.
(Hickories famously have a strong tap root
system, which can make transplanting a
challenge, so that if nurseries sell hickory
at all, they sell small, rooted seedlings.)
"We went into that first phase of research
thinking some individual shagbark hickory
individuals might be easier than others to
propagate, but producing fibrous roots—
that was totally unexpected," Nina says.
Overcoming tap root formation to produce
fibrous roots could be the key to successful
propagation, which means getting sale-
able-size hickories into the trade. The next
step for Nina and Brandon is to compare seed-
ling (sexually propagated by nuts) hickories
to layered (asexually propagated by layering)
hickories to see if the latter have better water
uptake and better transplanting success. >>
Three hybrid oaks developed by Nina and team; all are currently being trialed
in communities through New York State. Top-left: Quercus warei × comptoniae,
top-right: Q. macrocarpa × turbinella, and bottom-left: Q. bicolor × aliena.
Bottom-right: Shellbark hickory (Carya laciniosa) is one of the hickory
species for which Nina is most excited to develop successful propagation
techniques. Wikimedia, Douglas Goldman, USDA
CC BY-NC 4.0
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