Lynn Batdorf is a boxwood fanatic. For 27 years, he has been curator of the National Boxwood Collection at the U.S. National Arboretum in Washington, D.C.
He shared his knowledge of man's oldest ornamental plants during a slide lecture on boxwood's history, care and types at a meeting of the Frederick Area Landscape Contractors and Nurserymen organization at the Dan-Dee Country Inn in Frederick.
"Most boxwood you see has been cultivated," Mr. Batdorf said. The majority of the species lives in tropical areas, and only seven species are temperate and found in the United States.
According to the arboretum's Web site, its National Boxwood Collection is one of the most complete in the world with 150 different species and cultivars.
Boxwood is especially common in the mid-Atlantic region. It was first grown by Egyptians 4,000 years ago and is valued for its hard wood, medicinal purposes and permanence in the landscape.
Mr. Batdorf recently returned from a trip to Azerbaijan and the Republic of Georgia, where he identified and collected 85 boxwood taxa new to science. He has written nearly 80 technical articles and lectured widely on boxwoods. His third book, in which he discusses 417 cultivars of boxwood and 1,047 types, is being printed.
Mr. Batdorf is also curator of perennial and aquatic plants at the arboretum, which is the only federally-funded arboretum in the country. It is situated on 446 acres in northeast Washington, D.C.
History of boxwoods
References to boxwood are found in the Bible, and it has many religious connotations, Mr. Batdorf said. He believes it was boxwood, not palms, that were laid in the streets as Jesus rode a donkey into Jerusalem.
Boxwoods were known as palms. The wood is so hard and dense, it was once believed that evil spirits could not bore into it. Boxwood was probably used to cleanse the area of evil spirits.
"The wood is very, very dense," Mr. Batdorf said. "When cured, it shrinks. Woodcarvers go nuts over this. It's 2 1/4 times denser than oak."
In ancient times, the wood, often taken from boxwood reaching 60 feet in height, was used to make jewelry boxes and snuff boxes -- perhaps where its name was derived.
English boxwood is actually native to Southern Europe, Mr. Batdorf said. It was brought northward by the Romans.
As he spoke, Mr. Batdorf clicked through photos of boxwoods of different sizes, shapes and growing habits.
Buxus microphylla compacta is the slowest-growing type. Another type grows tall with perpendicular sides, while Japanese boxwood grows very wide and never taller than 10 feet. Another has a pendulous habit. There is groundcover boxwood and one with leaves resembling rosemary.
Variegated boxwood can have either white or yellow highlights. "The white is a little bit more striking," Mr. Batdorf said.
Caring for boxwoods
"I've had people say you should not mulch boxwood," Mr. Batdorf said, but most don't know the reasoning behind that bit of ill advice.
Boxwood mulching is usually feast or famine, with homeowners and landscapers using no mulch at all or or too much. He recommends a thin layer of shredded hardwood bark.
"Boxwood roots need to stay up close to the surface, that's why they need some mulch," he said. "It does so much to maintain a healthy root system."
Most of the annual root growth occurs from December to March, so fertilize boxwoods in the fall for strong and healthy roots, he said. Root growth slows and stops in the spring, so fertilizing only helps the foliage, stressing the plants.
Soil testing helps growers determine what plants need, Mr. Batdorf said. "I can't convince anybody to spend five bucks on a soil test."
Moving and planting boxwoods is also better done in the fall, he said. He showed a photo of a boxwood dug up with a huge, round rootball. He said the root ball would better serve the boxwood if it were pancake shaped because of the extensive root system, but root balls are just that -- balls.
Planting annuals close to boxwoods is a big no-no, because that chops up boxwood roots.
Don't plant boxwoods where they get too much sun, Mr. Batdorf warned. On warm winter days, boxwoods may think spring is here. Water may creep up into the stems, and when it freezes again, the bark may burst. Avoid siting boxwoods where there is a lot of afternoon sun.
"The big wild card is snow," he said. If boxwoods are used as foundation plants, they may be damaged as snow falls off rooftops. These may need to have the snow removed from them.
"If you placed them away from the foundation, do nothing," Mr. Batdorf added. It is a far safer practice to allow the branches to slowly return to normal after bending over in the snow as it melts.
Homeowners with deer problems can look to boxwood to help ease the damage, Mr. Batdorf said. "I've seen deer eat split-rail fences before they'll eat a boxwood. You won't have deer eat your boxwood, I can promise you that."
The yellowing of boxwood leaves is a common sight, but what is often overlooked are smaller leaves and wood that is turning orange, symptoms that boxwood is stressed, Mr. Batdorf said.
Pests like the boxwood "leaf miner" and mites can trouble the plants, but the biggest problem affecting them is browning. Discoloration of the plants is caused by lack of thinning, Mr. Batdorf said. "English boxwood should not be a thick plant."
If a boxwood is too thick, there is no air circulation in the center. That, coupled with moisture from dew, mist and rain, can lead to fungal disease. The arboretum received many calls this year on the subject because of the area's prolific rains.
"You should be able to see the stems inside," Mr. Batdorf said.
December is a great time to prune boxwoods. They should be thinned and not sheared.
"If you want to shear something, do it to a hemlock or a holly, these are lesser plants," the boxwood expert said.
Another characteristic of boxwood that is considered an ailment by some is the smell. In late March or early April, they flower and give off a scent. Sometimes, boxwood has a musky scent.
"Some people love it, some people hate it," Mr. Batdorf said.