The green brains of alien life forms scattered on the ground under certain trees are no cause for alarm. Actually, they are not alien brains at all, but the fruit of the osage orange, a tree common to hedgerows and roadside thickets in this area; and it is in autumn, as the golden-yellow leaves begin to fall, that the large fruit becomes conspicuous. You may find it still hanging on the tree, or lying underneath, or squashed to greenish pulp on the road by passing cars.
Osage orange is an interesting tree with a fascinating history. Its scientific name is Maclura pomifera, and it is a member of the mulberry family. You can see the resemblance to mulberry in the yellowish-orange wood and the milky sap it exudes when cut.
It is native to certain areas of Texas, Oklahoma and Arkansas, but was widely planted in the 19th century by settlers as a living hedge and is now naturalized in much of the eastern and Midwestern United States.
The wood is extremely strong, dense and split-resistant. The Osage tribe of Native Americans, who lived in its native range, prized its wood for making bows and war clubs; and the wood is still used to make the best bows for primitive archery. One of its common names, “bois d’arc,” means “bow-wood” in French; this has been corrupted to “bodark,” another name for this tree.
Its wood is valuable firewood, producing almost as much heat as coal. Because of its hardness, strength and beautiful orange-yellow color, the wood is prized for musical instruments such as violins and harps. In addition, the wood also contains a chemical that makes it highly rot and insect resistant, making it good for fence posts and outdoor furniture; it will last for many decades without decay or insect damage.
It is a tough, durable fast-growing tree, adaptable to a wide range of soil and moisture conditions. Its fibrous root system makes it easy to transplant. It will grow in just about any soil, from acidic to alkaline, clay to sand, and wet to very dry; and is extremely tolerant of drought, heat and wind. Even in the hottest, driest summer weather, its glossy green leaves remain fresh without wilting.
Osage orange grows as a wide-spreading tree, about 25 to 40 feet in height and width, its short trunk dividing into many limbs, forming an irregular crown of dense, interlacing, distinctly arching branches. And it is armed with short, stout thorns on twigs and smaller branches.
Before the invention of barbed wire in the 1880s, osage orange was used to grow thousands of miles of living hedge in the Midwestern plains; hence, another of its common names is “hedge-apple.” The saplings were planted close together in a line, then pruned to encourage bushy growth. The dense, thorny growth formed hedges up to 40 feet tall and 30 feet wide that were “horse high, bull strong, and hog tight.” With the advent of barbed wire, hedges were no longer needed, but osage orange was still useful for fence posts and windbreaks. The hedgerows that remain today are valued for wildlife cover.
Back to the fruit: osage orange is dioecious, which means that male and female flowers grow on separate trees, so the grapefruit-sized fruit only appears on female trees. It is round, up to 6 inches in diameter, lime-green with a wrinkled skin that reminds me of brains. It has a pleasant citrus smell, hence the name orange applied to it; the dense, white, sticky pulp inside is embedded with up to 200 small gray seeds.
Squirrels love these seeds, but have to wait until the fruit is ripe and soft enough to get at them; you may find piles of shredded fruit under the tree that indicate squirrels were at work. Although the fruits, once softened by frost, are eaten by cows, they are too large for wild animals such as deer to eat. Scientists theorize that these large fruits evolved to be eaten by large ice-age era mammals, such as horses, rhinoceros and mastodons, that are now extinct.
The fruit produces the same insect-repellent chemical that is found in the wood; laboratory research has shown that this chemical will repel spiders and many insects, such as cockroaches, crickets and ants. I don’t know if this has been tested in a home situation; but still, many people gather and place the fruit around the home to discourage insects. A whole green fruit supposedly may keep insects at bay for up to two months; cut up or mashed fruit may work for only a couple of weeks.
Should you plant this tree in your garden? Although it has many wonderful attributes, the thorns and the fruits are definite drawbacks to its enjoyment as a shade tree; sitting under a female tree in the autumn may prove extremely painful. There are thornless male cultivars, such as ‘Wichita,’ which could work in a landscape; but I think this is a tree best enjoyed in a naturalized setting. Just watch out for falling fruit.
Annette MaCoy is the consumer horticulture extension educator and master gardener coordinator for Penn State Cooperative Extension in Cumberland County. If you have garden questions, contact Annette at 240-6500 or by e-mail at email@example.com.