January 2010 Plant of the Month —
American Arborvitae

Some Arborvitae selections are valued for their striking colors,
for example the bright gold foliage of ‘Sunkist’.
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Submitted by Dr. Susan Hamilton   

The American Arborvitae (Thuja occidentalis) is an easy and adaptable evergreen that can thrive in almost any landscape situation. Hundreds of cultivars have been introduced which allow this native, northeastern U.S. plant to fill almost any landscape niche.

From miniature selections like ‘Mossy’ growing to just one foot tall and ‘Hetz Midget’ growing to two feet to ‘Green Giant’ growing up to 30 feet tall, these plants can fulfill many uses in the landscape. Cultivars also tolerate a range of soil conditions. American arborvitae can be found growing in the wild in swampy, damp conditions as well as in the dry cracks and crevices of rocky cliffs. It can equally tolerate a range of light conditions, thriving in light-shade to full-sun.

One of my favorite features of American Arborvitae is its fine foliage texture. The evergreen, scaly foliage grows in fan-like sprays making for a soft, fine texture. Some stellar selections are valued for their striking foliage colors too like the bright gold foliage of ‘Yellow Ribbon’, ‘Lutea’, and ‘Sunkist’; the orange-bronze color of ‘Rheingold’ and ‘Fire Chief’; and the showy variegated foliage of ‘Sherwood Frost’ and ‘Wansdyke Silver’.  I like to have a gold or variegated selection in my landscape to brighten up my winter garden.

Many different forms along with varied sizes and colors allow for a range of landscape uses of American arborvitae. For a privacy screen and nice backdrop plant, you can’t beat ‘Green Giant’, ‘Smaragd’  ‘Emerald Green’, and ‘Degroot’s Spire’. Round and spherical forms like ‘Bowling Ball’, ‘Rheingold’, and ‘Hetz Midget’ make good foundation plants or good decorative container plants. Pyramidal forms such as ‘Emerald Green’, ‘Sunkist’, and ‘Yellow Ribbon’ can make nice specimen or accent plants.   

For ideal performance, I recommend growing American arborvitae in a well-drained soil in full sun to part shade. Foliage density will loosen up in too much shade. In hot and dry weather, periodic, deep waterings are advisable, especially when these plants are grown as foundation plants. Maintain a good three- to four-inch layer of mulch around the plants. Fertilizer and pruning are not required, which is another added benefit!

Dr. Susan Hamilton is an Associate Professor of Plant Sciences and Director of the UT Gardens at the University of Tennessee Institute of Agriculture in Knoxville. The UT Gardens are open public gardens that serve public horticulture teaching and research needs. Locations include Knoxville and Jackson

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Contact:
Susan Hamilton, UT Gardens, 865-974-7324

Patricia McDaniels, UTIA Marketing and Communications Services,
615-835-4570