Judging from recent e-mail, many of you share an interest in the best choice of plants for informal hedges, in creating an evergreen wall to define the boundaries of the landscape or a tall screen to hide behind. Any plant that I recommend to fill these needs will have to deal with two hazards: desiccating winter winds and pruning shears. Only one species comes to mind: our native arborvitae (Thuja occidentalis), often called Northern White Cedar or just plain “cedar” by the locals.

First I should clear up the nomenclature. An arborvitae is not a cedar. True cedars belong to the genus Cedrus in which there are no species tolerant of Maine winters.

The common name “arborvitae” is steeped in history. A tea made from the needles was used to treat scurvy, a discovery made by Jacques Cartier’s sailors on their voyage to Canada in the 1530s. In Latin “arbor” is tree and “vitae” means life; the combination of these two words originated with the cured seamen who called the tree “l’arbre de vie.”

The growth habit of white cedar in Maine is influenced significantly by its environment. Plants growing on rocky upland sites are often stunted, resembling bonsai forms with twisted, forked and gnarly crowns. Plants growing in lowland areas are slender erect trees that typically reach about 60 feet in height.

The “needles” of white cedar are small overlapping scales arranged in flattened sprays. The apple-scented summer foliage is typically a soft yellow-green. In winter, however, the leaves of most trees turn more yellow, an evolved defense against excessive winter sunlight that otherwise could damage the light-sensitive photosynthetic system. What serves the tree, however, does not serve those people who desire dark green conifers in the winter landscape. Luckily there are a number of cultivars with darker green winter foliage (see sidebar).

Winter winds suck the moisture out of winter leaves while the roots lie encased in ice. This is the reason why there are so few broadleaf evergreen choices for Maine landscapes. And many of the needle-leaf conifers also suffer winter desiccation or “winter burn.” White cedar, however, takes Maine winters in stride, always meeting spring with all its limbs fully clothed.

For good reason, white cedar has become the best choice for hedging, both formal and informal. Even when shaped into flat-topped hedges that grow broader across the top than at the bottom, a result of misguided pruning shears, arborvitae struggles successfully to keep the lower light-starved leaves. Other species, subjected to such abuse, abandon the effort to produce leaves in the deep shade; the result is a “hedge on stilts.”

No doubt, our native white cedar is the plant of choice for hedging in landscapes characterized by hard winters and abusive pruners. Across the spectrum of hedging needs, from formal hedge defining a walkway to informal screen of tall trees, there is no better choice.

Send queries to Gardening Questions, P.O. Box 418, Ellsworth 04605, or to reesermanley@shead.org. Include name, address and telephone number.

Cultivars of Northern White Cedar for hedging and screening

Several cultivated varieties exist, selected for their growth habit and healthy green winter foliage color.

. Thuja occidentalis “Nigra” – upright columnar form with dark green winter foliage, to 20 feet tall by 4 feet wide

. Thuja occidentalis “Pyramidalis” – narrow pyramidal form that is very subject to winter burn, to 15 feet tall by 4 feet wide

. Thuja occidentalis “Smaragd” (also known as ‘Emerald’ or “Emerald Green”) – a relatively new introduction with emerald green foliage that retains its vibrant green color throughout the winter, narrowly pyramidal to columnar in growth habit, to 12 feet tall by 3 feet wide

. Thuja occidentalis “Techny” (also known as “Mission”) – a traditional cultivar with dark green winter foliage, to 12 feet tall by 4 feet wide, broadly pyramidal or upright oval in shape