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CRANBERRIES
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Highbush Cranberry
Viburnum trilobum, also known as Viburnum
opulus var. americanum L. Ait
Some Other Common
Names: American cranberrybush, guelder rose, dog rowan, *European cranberry
tree, marsh alder, rose elder, red elder, water elder, dog elder, gatten
tree, whitten tree, ople tree, snowball tree, crampbark
Introduction: The highbush cranberry is actually not a cranberry
at all, though its fruit, or “drupes” as they are known taxonomically,
strongly resemble cranberries in both appearance and taste. They also mature
in the fall, as cranberries do. The two plants are quite different, however.
Both are native to North America, but the highbush cranberry is a Viburnum,
a member of the Caprifoliaceae, or Honeysuckle family, in contrast to the
‘true,’ or ‘lowbush’ cranberry, which is a Vaccinium, a member of
the Ericaceae—Heather or Heath—family. The Honeysuckle family is comprised
of about 400 species, with 11 tree species—and numerous shrub species—that
are native to North America. They are located mostly in north temperate
regions and in tropical mountains. In North America, the highbush
cranberry stretches from British Columbia east to Newfoundland, south to
Washington state and east to northern Virginia, with an isolated population
in New Mexico. According to the Natural Resources Conservation Service,
the highbush cranberry is listed as ‘endangered’ in Indiana, ‘threatened’
in Ohio, and ‘rare’ in Pennsylvania.
Plant Description: Considered a large and hardy deciduous shrub
with a moderate growth rate of up to 3 ft. per year, the plant is typically
8 to 15 feet tall by 8 to 10 feet wide, with arching stems and a very dense,
rounded form, making it a popular landscaping choice for use as a screening
hedge [For a solid screen, plants should be spaced 2 to 3 ft. apart.].
It is noted for attracting wildlife, especially birds which benefit greatly
from the fruit, which can remain on the branches well into mid winter.
It is tolerant of frost, likes sun or semi-shade, and is successful in
most soil types but does best in well-drained, moist soil that is rich
and loamy. Established plants can tolerate drought, but they are
helped by supplemental watering during such periods.
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Leaves: Opposite, simple, 3-lobed and 2 to 4 inches long. They are
superficially similar to many maple leaves, but have a somewhat wrinkled
surface and impressed venation. They are glossy dark green in the
summer but often change to yellow-red or red-purple in the fall. The petiole
is grooved and has round, raised glands near the base.
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Flowers: It produces flat-top clusters of showy white flowers in
June. The clusters are 2 to 3 inches across, with an outer ring of larger,
sterile flowers. Although the flowers are hermaphrodite (having both male
and female organs) and are presumably self-fertile, there is some debate
about that so it is probably best to grow at least two different cultivars
in order to ensure fruit and fertile seed production. The flowers
are also pollinated by insects.
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Fruit: Nearly round drupe (drupe: a fleshy fruit with a central
stonelike core containing 1 or more seeds) about 1/3 inch diameter with
a single large seed, bright red, juicy and quite acid, like a cranberry.
The seeds ripen from August to September. It does not begin to produce
fruit until approximately five years of age.
Edible Qualities: The fruits/drupes can be eaten raw or cooked,
and like cranberries, they are rich in vitamin C and so have a tart, acid
taste (the taste is best after a frost and when picked slightly under-ripe).
They are an excellent substitute for cranberries and are likewise used
in preserves, jams, sauces, etc., which make delicious condiments for meat
and game. The jam is said to have a very pleasant flavor.
Insects: Reported to have very few insect problems in general,
but one insect in particular—the Viburnum Leaf Beetle (Pyrrhalta viburni
P.)—is capable of completely defoliating highbush cranberry stands (complete
defoliation has been witnessed in Maine). Both the larvae and adults of
the beetle feed on the leaves, severely skeletonizing them. The trees can
survive this injury, however, and go on to leaf out normally again the
following year. Severe damage inflicted yearly, however, will kill the
tree. The Viburnum leaf beetle was introduced from Europe, and in
fact the first North American populations of the beetle were discovered
on European highbush cranberry plantings in the Ottawa/Hull region of Canada.
There are several fact sheets about the Viburnum leaf beetle on the web,
including these by Cornell Cooperative Extension and UMass Extension:
http://www.entomology.cornell.edu/public/IthacaCampus/ExtOutreach/DiagnosticLab/Factsheets/VLBfactsheet2003.html
http://www.umassgreeninfo.org/fact_sheets/defoliators/viburnum_leaf_beetle.html
NOTE: *There is also a European variety of highbush cranberry
(Viburnum opulus) that is said to produce inedible fruit.
LEFT: Highbush cranberry shrubs in central Maine defoliated
by Viburnum leaf beetle larvae.
RIGHT: Four Viburnum leaf beetle larvae feeding on a branch
of one of the highbush cranberry shrubs shown
at left. With all of the leaves already consumed, these larvae were
feeding on the bark and inner branch tissues!
If you have comments or questions about this page,
contact Charles Armstrong at: charlesa@umext.maine.edu
Putting
knowledge to work with the people of Maine
