Nina is also looking forward to continuing her own work
on propagating unusual shrubs, ones that you don't
often see in nurseries because they are hard to propa-
gate. She's working on white forsythia (Abeliophyllum
distichum), which blooms two weeks before forsythia
and is quite fragrant. She's also working on Chinese
fringetree (Chionanthus retusus) and white fringetree
(C. virginicus), both extremely difficult to propagate.
She would also like to find a way to successfully prop-
agate spicebush (Lindera benzoin). "My graduate
student, Caroline Stokes, has had good success rooting
spicebush," Nina says. "My goal is to propagate desir-
able plants for greater availability in the trade."
As much as plant propagation and tree selection for
stress tolerance has been a major feature of Nina's
work, the issue of soil remediation is equally if not
more important to her. Urban soils are commonly
degraded and compacted so that no tree, no matter how
tough, will grow well without intervention. Moreover,
soils under pavement require compaction to bear the
weight of pavement. To meet this challenge, she and
colleagues developed
CU-Structural Soil, a soil that
is made to be placed under pavement to meet engi-
neering specification for load-bearing—while allowing
tree roots to grow through it. CU-Soil has been used
by about 2500 communities all over North America,
according to Nina. There is still more research to do on
the potential addition of biochar to CU-Soil to increase
its water holding capacity; this work is ongoing.
A technique Nina and colleagues developed for reme-
diating compacted soil wherever soil doesn't have
to support pavement, called "Scoop
and Dump" or
"Amend Soil in Place," has proven itself in research
and application. "After urban development, soils are
generally trashed," Nina says. "We've found that by
adding about a third by volume of compost and incor-
porating it to a depth of about 18 inches (46 cm),
soil compaction is eliminated and soil texture con-
tinues to improve over time. We've used 'Scoop
and Dump' on the Cornell campus for the last 20
years, and the long-term results are impressive."
Nina hopes to carve out time to write a guide to this
technique for practitioners and communities. >>
"White fringetree (Chionanthus virginicus) (left) is exceedingly difficult to propagate," Nina says. "I would really like
to figure this one and Chinese fringetree (Chionanthus retusus) (right) out so they can be more readily available
in the trade." Photo of white fringetree by Michelle Sutton; photo of Chinese fringetree by Bill Haws.
32 CityTREES
