University of Vermont Extension 
Department of Plant and Soil Science

Winter News Article


CARY AWARD WINNERS FOR 2009
 
Dr. Leonard Perry, Extension Professor
University of Vermont
 
 
In New England, several choice trees and shrubs are given the Cary Award each year.  Winners for this year include a tree and a group of shrubs you don't usually think of for the north.
           
The Black Gum or Tupelo (Nyssa sylvatica) is a deciduous (loses its leaves in winter) tree reaching 40 to 60 feet tall, and half as wide.  Hardy to USDA zone 5, its attractive but non-distinct dark green leaves are one of this plant's main attributes with their brilliant fall colors.  The common name of this native tree to the eastern U.S. is from the Creek language meaning "tree of the swamp."  Although another related species grows in wet areas (hence the genus name too, for the Greek water nymph Nyssa), particularly in the south, this one grows on drier soils as its species name indicates ("sylvatica" means "of the woods").  When I was growing up in the South, this was one of my favorite trees.
           
A group of shrubs, generally thought of for southern gardens, but winning the Cary award this year are the Boxwoods.  Most of the more hardy selections for northern gardens (zone 4) are selections of the Korean boxwood (Buxus sinica var. insularis), formerly known by a different scientific name (Buxus microphylla var. koreana), or hybrids of this and the southern Common Boxwood (B. sempervirens).  'Green Gem is perhaps the lowest, slowly reaching two feet tall and wide.  Forming a slightly taller globe shape (three feet) is 'Green Velvet'.  Taller yet is 'Green Mountain', forming a pyramid five feet or more tall, and half as wide. 
           
'Verdant Hills' is a slow-growing introduction from the University of Vermont about 30 years ago.  It is quite hardy (zone 3), and reaches three feet tall and about twice as wide. 
           
Similar to 'Green Velvet' is a faster growing introduction from the Chicagoland Grows program of the Chicago Botanic Garden.  Chicagoland Green®, also know as the cultivar 'Glencoe', has excellent dark green winter color.  Another cultivar of the Korean boxwood with good green winter leaf color is aptly named 'Wintergreen'.  Good winter leaf color is important when choosing plants, as some selections of hardy boxwoods "bronze" or turn unattractive brownish yellow from winter sun and winds.
           
In the north, these hardy boxwoods grow in full sun to part shade.  New plantings may benefit from shade until established.   To keep leaves from bronzing in winter, plant in protected sites or use burlap screens.  Boxwood prefer moist, well-drained soils.  Mulch to keep soil cool.  
           
Although flowers are insignificant aesthetically in the landscape, they are significant to bees.  Watch for cupping leaves, which is often a symptom of insect damage by the boxwood psyllid.  When pruning, some people may have an allergic skin reaction to the sap.
           
Boxwood are adapted to pruning, or more commonly shearing (uniformly cutting back all branches such as with hedge shears).  If starting with new plantings, choose cultivars for the shape you desire to avoid having to shear.  Low boxwoods form hedges along walks, taller ones form a background in borders or along foundations of homes. 
           
To learn more about boxwoods, visit the website of the Boxwood Society (www.boxwoodsociety.org).  Also see past Cary winners online (www.caryaward.org).
            

Return to Perry's Perennial Pages, Articles uvmext logo