The star-crossed honeylocust – In Profile
The story of the native honeylocust’s (Gleditsia spp.) rise in America has more twists than a John Grisham novel. Also called the sweet locust, thorn tree, three-thorned acacia, and honey shucks, the tree seemed destined to be an agricultural star in the 1920s when USDA researchers determined that its seed pods offered a valuable option for cattle and pig fodder.
At that time, one acre of honeylocust trees could produce almost twice the volume in fodder of one acre of corn or oats. It also contained two to three times the sugar content of sugar cane or sugar beets–think sugared cereal for cows.
Honeylocust seemed to offer an opportunity for a cost-effective, superior feed for livestock, and serious energy was spent in the 1930s trying to breed the best of the species for agriculture. Four or five acres of test trees were planted across the Potomac River from Washington, DC, in Arlington, Virginia.
But problems cropped up in the 1940s and doomed the honeylocust’s future in agriculture. The test field became the Pentagon. After World War II, the USDA and American farmers shifted to using chemical fertilizers and pesticides, vastly increasing yields of row crops and rendering the honeylocust unable to compete.
HOMEOWNERS TO THE RESCUE
At this same time, though, the common honeylocust began to be eyed as a possible home landscape tree. The key to its potential popularity could be summed up by the adjective “thornless.” Most native honeylocust species have serious thorns on their roots, trunks, and branches, hut the nursery industry cast an approving eye on the thornless common variety (Gleditsia triacanthos), specifically the variation called ‘Inermis.”
Easy to care for and possessing good resistance to insects and disease, this honeylocust had lovely foliage and flourished in a wide range of soil types. These attributes made it a natural, and the common honeylocust became a popular ornamental replacement for the disappearing American elm. (Elms were dying of the still-incurable Dutch elm disease.)
Because thornless honeylocust are adaptable to urban conditions, they have frequently been used as street trees. But popularity is a two-way street, and an overabundance of the trees in some areas has led to increasing insect and disease problems.
Common honeylocusts are fast growers–between 2 and 2.5 feet per year during the first 20 years–and spread as wide as they are tall. Horizontally growing branches give them a tiered and flat-topped look. They reach maturity at 100 to 125 years.
Honeylocusts are deciduous, so they lose their leaves in autumn. Foliage emerges in spring, usually late May, as many elongated, oval leaflets arranged opposite each other along 8-inch stems. There might be as many as 20 to 30 leaflets on a stem, with some trees having double leaves. But because the foliage is so lacy and light, honeylocusts do not give much shade.
New leaves are light green, turning yellow-green during the summer, and then scarlet in early autumn, making a gorgeous display when backed up by large still-green trees. Females of the species produce fruit in the form of seed pods that are 10 to 15 inches long, depending on the species.
Male and female honeylocust flowers both bloom in June. They emerge in separate clusters on the same tree. The most obvious are the yellow-green clusters of male flowers, called catkins. They hang about 2 inches or more long and give way in late July to bean-like, flat pods that hang 12 inches or more from the tree. These purplish-brown pods persist until mid-January when they finally drop.
Honeylocust wood is strong, hard, and durable. With its natural shock resistance and attractive reddish-brown grain, it’s used for fence posts, general construction, pallets, crating, and railroad ties.
You can produce honeylocust trees by budding with scionwood taken from the thornless upper branches of selected cultivars, however, these seedlings will be thorny.
Among the thornless varieties, “Inermis” is a spreading, rounded tree that can grow to be 100 feet tall with a spread of up to 70 feet. Flowers are inconspicuous, but the long, pea-like pods develop in the late summer and persist into late autumn, sometimes dangling from the branches into early winter. Autumn color is a warm, golden yellow.
The following honeylocust varieties do not produce seed pods:
* “Cottage Green”: semi-upright; seed less.
* Halka”: a strong, vigorous tree; occasionally produces fruit.
* “Imperial”: symmetrical and corn pact, broad crown.
* Majestic”: upright
* Moraine”: an early cultivar; standard; deep green foliage turns to yellow in autumn; a favorite of municipal arborists.
* “Shademaster”: an old reliable; good form, ascending branches; virtually no pods although can begin developing them after 15 years.
* “Skyline”: erect, pyramidal, with good autumn color.
* “Sunburst”: smaller and more com pact than others of the species, this tree is fast-growing and will reach 30 to 40 feet with a crown spread of 25 to 30 feet; bright yellow leaves emerge in spring and mature to light green by summer.
IN THE YARD
Honeylocust is fairly resistant to salt, drought, soil compaction, heat, and disease, which makes it a good choice for specimen trees in the yard or garden. Because honeylocust provides very light shade, it’s possible to grow grass or flowers under it with little problem.
Honeylocust also makes an apt screen along property lines or can be used as a windbreak at the edges of fields. The trees are appropriate for parks, but the thorny varieties should be avoided because of the potential hazard they can pose to children and animals.
If you enjoy flower arranging, the dried pods of the “Inermis” variety make wonderful material. Also, the pods tend to rattle on the trees in the winter wind, giving the tree some extra interest.
Honeylocusts grow best in full sun but tolerate light shade. Their natural habitat is rocky hillsides, open or wooded pastures, fence rows, and around abandoned fields where they serve as windbreaks in the Midwest. They prefer well-drained soil–either fine sandy clay or heavy loam that is slightly acid to neutral (pH 6.1 to 7.5)–but will grow in almost any soil so long as it’s not too wet or acidic. The trees should be planted in spring or autumn. They grow throughout the Midwest from the Gulf of Mexico (zone 9) north to the southern Michigan border and east up into New England (zone 4). They can withstand winter temperatures that dip to -20 degrees F. or more.
This tree needs no special care over and above normal pruning of damaged limbs and watering during drought. Note, though, that it has become more vulnerable to insect and disease problems because it is so frequently planted. Of these pests, the mimosa webworm is the most serious, especially for thornless varieties.
Other pests include gypsy moth caterpillars, gall midge, and scale. While relatively disease-free in their natural habitat in the wild, cultivated honeylocusts are sometimes victims of a canker disease caused by a fungus and linked to drought stress. There is some suspicion that cankers, or sores, may also be caused by pruning wounds or sunburn.
The honeylocust has been on a roller coaster ride of potential and real stardom over the last 80 years or so. Interestingly, two common honeylocusts on the East Coast are duking it out for stardom of a different sort.
The national champion common honeylocust–the one AMERICAN FORESTS judges to be the biggest based on a formula of its height, circumference, and crown spread–is located in Frederick County, Maryland (see statistics on page 49 or www.americanforests.org for more on AMERICAN FORESTS’ National Register of Big Trees). Maryland’s tree is being challenged for that title by another monster honeylocust in Virginia. Which will win the crown? Stay tuned for the 2004 National Register of Big Trees, due out next spring.
In the meantime, if you live in an area where the honeylocust is not so very common, you might consider planting this true landscape star.
THE NATIONAL CHAMP
Location: Frederick County, Maryland
Circumference at 4.5 feet: 226 in.
Height: 100 feet
Crown spread: 88 feet
Total points: 348
Nominator: Gary Schmidt
The National Register of Big Trees is sponsored by The Davey Tree Expert Company.
“Yardening” expert Jeff Ball writes from his home in Attica, Michigan.
COPYRIGHT 2003 American Forests
COPYRIGHT 2003 Gale Group