All About Boxwood (Buxus)


Boxwoods (buxus) are a genus of evergreen shrubs and trees. They are known worldwide for their usually compact size and small, leathery leaves. Steeped in a rich tradition and heritage these versatile shrubs have graced the homes of royalty and peasants alike.

History 
Fossilized remains of buxus plants date back to over 22 million years ago. In 4000 B.C. Egyptians used clipped box hedges in their gardens, as did Emperor Augustus during his reign of the Roman empire in 27 BC-14 AD. Since those times there has been a rich documented history of the use of buxus in the landscape. Boxwood was introduced to North America from Europe in the mid-1600’s, where it continues to be utilized in both traditional and contemporary landscapes.

Boxus Wood
 The word buxus is Latin for the word box and is thought to have been named for its common use in the making of highly decorative boxes. Owing to its very fine texture and exception hardness buxus wood is particularly well suited to carving. It is one of the few woods that are denser than water. Boxwood has been used to make recorders, combs, printing blocks and handles for tools. Today boxwood is commonly used to make highly detailed chess pieces and parts for musical instruments.

Breeding
According to the American Boxwood Society there are about 90 species of boxwood world-wide and over 365 cultivars (148 of which are currently available commercially). Most of these species are tropical or sub-tropical but there are a few species and several notable varieties and cultivars that are suitable for North American climates.

Popular Selections for North American Gardens
English Boxwood: (Buxus semperviren ‘Suffruticosa’)
Often referred to as common boxwood, this species is native to Europe, North Africa and Western Asia. Most notable characteristics of this dwarf cultivar include a tight growth habit and slow growth rate (averaging only 1” of growth per year with a mature height of 3’). English boxwoods have a tendency to bronze in the winter and mature shrubs are susceptible to boxwood decline, especially when grown in full sun.

American Boxwood: (Buxus semperviren ‘Arbvorescens’)
This is a faster growing cultivar with a looser growth habit. Average height 5’-10’; oval in shape; leaves pointed

Japanese Boxwood: (Buxus microphylla var. japonica)
Commonly referred to as little leaf boxwood. Native to Japan and Taiwan this species is more tolerant of heat and drought, but like the English has a tendency to bronze in the winter. Growth habit is compact and rounded averaging 3-5’ in height.

Popular Hybrids: The green series introduced in Ontario by Sheridan Nurseries are a cross between Buxus microphylla var. koreana and Buxus sempervirens. These boxwoods are more cold hardy with less winter bronzing and tolerate full sun better than many varieties. Their growth habit is compact and fairly dense and tend to require little pruning, although they can be easily sheared to desired shapes. Green Velvet, Green Mountain, Green Gem and Green Mound are four 4 popular cultivars from this collection. Other popular hybrids include: Korean Boxwood (Buxus microphylla var. Koreana), Chicagoland Green ® (Buxus x ‘Glencoe’) and Boxus microphylla var. japonica ‘Green Beauty’ (also known as Boxus harlandii).

Cultural Practices
Light requirements
: Boxwood will grow in full sun but prefer part shade. (Some cultivars tolerate more sun than others. i.e. the green series hybrids prefer more sun.)

Soil pH: Boxwood prefer a soil pH between 6.5 and 7

Moisture: Moist well drained soil is preferred. Boxwood hate wet feet and are highly susceptible to root rot when grown in standing water.

Propagation: Stem cuttings are the most common technique but layering is also an option. When selecting stems to cut choose smaller 1-year old branches, they are said to have a higher concentration of growth hormones. Non hybrids can be grown from seed, to do this scarify the seeds and plant them at a depth of about 1”. Germination will take anywhere from 30 to 190 days. 

Mulching: Boxwoods are shallow rooters and benefit from a shallow layer of mulch to protect the roots. Deep mulching should be avoided as it may encourage roots to grow above the soil surface putting them at high risk of damage when dried out. 

Salt spray: Most boxwood are very sensitive to the salt spray from roadways, plant them far enough away from these areas to avoid injury.

Poisonous leaves: The leaves of boxwood contain steroidal alkaloids making them mildly toxic to both humans and animals.

Pruning: Boxwood can take repeated close shearing making them a popular choice for topiary, bonsai, and formally clipped hedges and shrubs. Species and cultivars (such as Buxus sempervirens) with a dense growth habit benefit from thinning to open up their centers to better air and light circulation. This encourages growth of leaves on the interior and may help to reduce disease.

Potential Problems
Boxwood blight: a fungal disease causing rapid and severe defoliation.  Caused by the pathogen, Cylindrocladium buxicola. Symptoms first appear as leaf spots that are light to dark brown, with or without a dark border, as well as stem lesions or cankers. After infection has taken place white spore masses develop on the undersides of leaves. Wounding is not required

Volutella blight: a less serious fungal disease caused by the fungus volutella buxi. Symptoms include salmon coloured cushions on lower leaf surfaces and some stems, followed by yellowing and then leaf and stem death. Black streaks are sometime visible on petioles and stems. Unlike boxwood blight wounding is required for this infection to take place. Volutella buxi requires 18 hours of wet conditions in order to germinate.

Spider mites: leaves of injured plants appear stippled.

Phytophthora root rot: Caused by the fungi, Phytophthora. Plant boxes in well drained soil to help prevent this disease. Buxus sempervirens ‘Suffruticosa’ and Buxus sempervirens ‘Arborescens’ are most susceptible.

Winter Bronzing: leaves turn a bronze colour as the result of exposure to cold, dry winter winds. Plant boxes in a sheltered spot or place physical barriers (about 18” away from the plant) on the windward side to protect them.

Nematodes: these microscopic, worm-like organisms feed on the roots. Plants appear to be in decline and appear smaller than normal.

Leaf Miner: damage appears as blotch mines between the upper and lower leaf surfaces. American boxwood tends to be the most susceptible.

Boxwood decline: older English boxwoods, particularly those grown in full sun and drier soils, show a slow progressive decline.

Psyllid: Feeding of this insect causes the outer leaves to curl and form a cup which encloses the nymphs. 

In spite of these potential problems boxwood remain a popular and easy to grow shrub. Whether you are looking for an evergreen to naturalize, a small tidy tree or a highly ornate shrub, boxwood has a species or a cultivar to suit almost any landscaping need.

Photo credit: all photos have been taken by and are the property of the author.

Resources:
Books

  •  Diseases and Pests of Ornamental Plants (fifth edition); Pascal P. Pirone; The New York Botanical Garden 1978 
  • Lois Hole’s Favorite trees & Shrubs; by Lois Hole with Jill Fallis; 1997 Lois Hole and Lone Pine Publishing
  • Ever Green Shrubs; Alexandria, Va.; Time Life Books 1989

Articles

  •  Growing Boxwoods in the Landscape; Erv Evans, extension Associate; Richard E. Bir, Extension Specialist; Stephen Bambara, Extension Entomology Specialist; Department of horticulture Science, North Carolina Cooperative Extension Service (revised 2/99)
  • Major Diseases of Boxwood; Mary Ann Hansen, Extension Plant Pathologist, department of plant pathology, Physiology and Weed Science, Virginia Cooperative Extension, Virginia tech, and Virginia State University, May 2009
  • Volutella blight of boxwood; Fang (Amy) Shi and Tom Hsiang; School of Environmental Sciences, University of Guelph

Websites

http://www.boxwoodsociety.org/

http://www.sheridannurseries.com/plant_product_refine_search#//boxwood

http://www.thepruningschool.com/Articles/boxwoodPruning.htm

http://www.wisegeek.com/what-is-an-english-boxwood.htm

http://www.wisegeek.com/what-is-an-american-boxwood.htm

http://www.wisegeek.com/what-is-a-Korean-boxwood.htm

http://www.wisegeek.com/what-is-a-Japanese-boxwood.htm

http://www.wisegeek.com/what-is-a-green-mountain-boxwood.htm

http://www.wisegeek.com/what-is-a-green-velvet-boxwood.htm

http://www.wisegeek.com/what-is-a-green-gem-boxwood.htm

http://www.wisegeek.com/what-is-a-winter-gem-boxwood.htm

http://www.englishboxwoods.com/?page_id=143

http://www.monrovia.com/plant-catalog/plants/410/dwarf-english-boxwood.php

http://en.wikipedia.org/wiki/Buxus

http://en.wikipedia.org/wiki/Buxus_sempervirens

http://en.wikipedia.org/wiki/Buxus_microphylla

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Terms of use: photos and content may be used for non-profit use and education with proper attribution and link back to page found.

For photos: Kimberley Pacholko All About Boxwood (Buxus) – Horticulture For Home Gardeners

For content: Kimberley Pacholko 2021, Ornamental Garden Specialist, All About Boxwood (Buxus) – Horticulture For Home Gardeners

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