Flowering Colvillea racemosa fronting St.
John Plant Science Laboratory.
The right tree for the right place: this is
horticulturalist Richard Criley’s focus. Both the location—away from utility
lines, not too close to a sidewalk or drainage lines, positioned to provide
shade where needed or to enhance a landscape with its beauty—and the tree
choice itself—size, canopy density, flowering, fruiting, amenability to
pruning—can influence the decision to plant a tree, and which tree to plant.
Some of the most appropriate, and loveliest, of the available trees are rarely
planted, however. Hawai‘i’s landscape architects tend to select from the same
relatively small group, explains Dr. Criley, emeritus professor in the
department of Tropical Plant and Soil Sciences, because these have worked for
them in the past. Adventuring into new trees is often frowned upon by landscape
firms, in case they may not work out and the firms are blamed.
Dr. Criley poses with an Erythrina abyssinica,
which he propagated from seed. The tree, a relative of the native wiliwili, was
planted in 2012 to commemorate the 150th anniversary of the establishment of
the land-grant university system and the USDA.
There are many reasons to
choose alternate trees, however. One is the growing interest in utilizing
native plants, which not only may have cultural significance but tend to be
better suited to the climate and other conditions than imports, requiring less
water, fertilizers, and pest-control measures. Another important reason to
diversify has been the impact of invasive insects on popular trees. For
instance, the Islands have been affected by the monkeypod defoliator, lobate
lac scale, Erythrina gall wasp, and a similar pest affecting Chinese banyans.
When a common type of tree has to be removed due to insect damage, it’s
noticeable in a landscape without a wide variety. Most recently, the rhinoceros
beetle that attacks coconut palms has become a concern. Hawai‘i is fortunate
that coconut yellowing, which has decimated coconut palms across the southern
part of Texas and Florida, has not yet been found in the state, as it would
hugely impact the landscape and would also affect the native loulu palms.
For these reasons, Dr. Criley initiated a
project to identify tree species that could be used to diversify local
landscapes. He and his collaborators have developed more than twenty information
resources, available through CTAHR’s free publications, to help landscape
architects and homeowners choose alternatives to some of the most commonly
planted trees. These include the gorgeously flowering Colvillea
racemosa, the fragrantly scented lechoso, and
look-alike alternatives to popular choices, such as the native alahe‘e rather
than the imported mock orange. With such a range to choose from, consider
planting a new tree today!