11/17/2023

Osage Orange

In our continuing effort to promote tree benefits through research, technology, and education, the Ohio Chapter of the International Society of Arboriculture (ISA) provides Tree-of-the Month articles.  This month’s tree is Maclura pomifera, commonly known as Osage-orange or Hedge-apple.

SPECIES: “Horse high, bull strong, and pig tight”, is how Osage-orange was described by an Illinois College biology professor in 1847 to promote it as a living fence to America’s farmers.  The accuracy of this statement helps explain how a tree with such a limited native range is now naturalized throughout most of the United States.

Osage-orange (Maclura pomifera), also commonly known as hedge-apple, is neither an orange nor an apple, but a member of the Mulberry family.  It is a medium-sized, short-trunked, dioecious tree (male or female plants) with many crooked interweaving spiny branches that form a dense, spreading round crown.  Female trees produces its namesake orange-shaped fruit.  Its natural range is narrowly confined to the Red River drainage of Oklahoma, Texas, and Arkansas, but because of its adaptability, form, longevity, and durability, it has been planted extensively throughout the United States.

Native Americans, such as the Osage Indians (hence part of the common name), made bows and war clubs from the tree, while early pioneers found its decay-resistant wood ideal for making hubs and wheel rims, mine timber supports, and fence posts.  By the 1850’s, Osage-orange made the fencing of entire farms possible before the availability of barbed wire.  It was also the primary tree used in FDR’s "Great Plains Shelterbelt".   Beginning in 1934, 220 million trees stretching 18,600 miles were planted for windbreaks in response to Dust Bowl soil loss.  Osage-orange’s ability to address many pioneer and farming needs coupled with its ease of planting, alkaline soil tolerance, and drought resistance, resulted in it being planted in greater numbers than almost any other tree species in North America.    

As a side note, the genus “Maclura” was named for William Maclure (1763-1840), known as the ‘father of American geology’.  

LEAF:  The simple leaves are alternately arranged and can be clustered on lateral spur shoots.  The shiny dark green leaves (like a mulberry) that are 3–5” long by 2–3” wide, with an ovate shape and pointed tip.  When broken, the petiole produces a milky sap.  Leaf margins are smooth and somewhat wavy, and in the fall, leaves usually change to a good clear yellow color.

TWIG AND BUDS:  Osage-orange twigs are moderately stout with a tannish brown color that exudes a milky sap when cut.  The alternate lateral buds are small, round, and nearly embedded in the twig.  Its terminal bud is missing.  Sharp spines (modified leaf, petiole, or stipule) at the base of the buds or leaves are its most interesting twig feature.  Since most animals won’t eat Osage-orange fruit, and plants primarily arm themselves as protection from hungry animals, why are there sharp spines on their branches?  One theory is that Osage-orange armed itself against feeding from extinct megafauna, such as the American mastodon and the giant ground sloth.  These large mammals would eat, digest, and excrete the fruit and thus help spread their seeds.  Once these mammals were extinct, Osage-orange seeds were unlikely to spread by any other means than water, which might explain why their native range is limited to river valleys.  Knowing that native and/or naturalized trees are armed is always important to arborists responsible for the tree’s care or removal.

BARK:  The bark on young twigs tends to be a greenish-brown color, and sometimes tinged with yellow.  Trunks on older trees are deeply furrowed exposing an orange-brown underlying tint.  This bark contains tannin and was once used for tanning leather, while its bright orange root bark was used to produce yellow dye.   

FLOWERS:  Osage-orange is dioecious, with male and female flowers on separate trees.  During late spring or early summer, flowers are cross-pollinated by the wind.  Male flowers soon fade away, while their female counterparts develop into sphere-shaped fruits (compound drupes) that enlarge throughout the summer.  Each flowerhead has up to 200 female flowers that are compressed tightly together.   

FRUIT OR SEEDS:  When viewed from a distance, mature fruit resembles an orange, hence one of its common names.  The specific epithet “pomifera” means pome or fruit bearing.  Osage-orange is dioecious, and fruits on female trees are not single drupes like a peach, but rather tightly packed aggregates of many one-seeded drupletees.  The round, wrinkled, pale green fruit is roughly 4 to 6” in diameter and oozes a bitter milky juice when opened.  Each fertile fruit contains up to 200 seeds and resembles a large orange or a giant round mulberry.  Fruit is produced every year, ripens in September, and eventually falls to the ground.  Fruit weight prevents natural dissemination beyond parent trees except where animals move and cache fruits or where flood waters wash fruits downstream.  Osage-orange trees are usually sexually mature by 8-12 years of age.  Female trees will produce fruit without the presence of male trees, but no viable seeds will be present.  Fruits are pulpy, dense, and have a high content of milky, bitter, latex-containing sap.  Except for squirrels and some birds, few animals consume the seeds, which are the only edible part of the fruit.

SHAPE:  Osage-orange would never be referred to as stately.  It has a low round form consisting of a short trunk which often divides into several prominent upwardly arching armed branches.  Due to its form, and the fact that it suckers freely, Osage-orange can create an impenetrable barrier useful for corralling domestic animals.        

MATURE HEIGHT:  Osage-orange is considered a small to medium size tree that grows rapidly to a height of 30–40’, with a branch spread of 20–40’.  According to the Ohio Department of Natural Resources’ Champion Tree registry, Ohio’s largest Osage-orange is in Hamilton County measuring 75’ in height, with an 81’ crown spread, and a trunk circumference of 263”.

WOOD PROPERTIES:  Osage-orange heartwood is golden to bright yellow but fades to brown with sunlight exposure.  It is extremely durable and considered one of the most decay-resistant woods in North America.  Because of their strength and flexibility, Osage-orange branches were used by Native Americans to make bows, while its heavy wood was used for war clubs.  This latter fact was not lost on US law enforcement as the dense wood was also used to make police billy clubs.  With the innovation of barbed wire, planting Osage-orange as a living fence was no longer necessary.  But, because of its decay-resistant properties, Osage-orange wood was extensively used as posts for the ubiquitous wire fences.  It was often noticed that Osage-orange posts outlasted the barbed wire.  Because Osage-orange produces more BTUs when burned than any other domestic hardwood, it is sometimes used as fuelwood.

CULTIVARS:  While commercial, utility, and consulting arborists primarily focus on the native Osage-orange, municipal arborists are more concerned with the proper placement, installation, and maintenance of its cultivars.  ‘Park’, ‘White Shield’, and ‘Wichita’ is the best-known male (fruitless) and thornless cultivars.  Of these, ‘White Shield,’ a male clone found along the White Shield Creek in western Oklahoma, is most often used in urban/suburban settings.  The lack of messy fruit and hazardous thorns (mostly), coupled with its heat and drought tolerance, dark glossy green leaves, medium stature, upright form, and ease of planting, make this an important element in any municipal arborist’s plant arsenal.  Although not endowed with a central leader, the upright arching branches of ‘White Shield’ provide unencumbered vehicular and pedestrian flow, while offering good visibility for street signs and traffic.       

COMMENTS:  While Native Americans had a long history with Osage-orange in its natural range, it was the early pioneer responsible for its relocation to wherever decay-resistant wood for tools and wood products was desired.  Additionally, its use as a living fence and windbreak helped protect soils and farmsteads throughout the nation.  So, if you come upon this well-traveled tree while wandering along a country lane, it’s probably there due to a farmer.  But, if one of its cultivars is gracefully growing along a community street or in a park, you can thank a municipal arborist.

“The fruitless and thornless Osage-orange cultivars are an important component of any viable urban forest.  Their ease of planting, urban tolerance, rapid growth, and upright branching make them a valuable asset for current and future streetscapes.”  Tyler Stevenson, National Program Specialist, Urban & Community Forestry USDA Forest Service

​Tree Selection Tips: The Ohio Chapter ISA recommends working with an ISA Certified Arborist when selecting or caring for any tree in your landscape. To better guide you on the vital plant information for the Kentucky Coffeetree use our friendly users' guide below:

Photograph sources Andrew Todd 2023
Written by Andrew Todd, Former State Urban Forestry Coordinator; reviewed by Mark A. Webber, BCMA, CPH, LTE, MArborA, OCMNT, RCA, TPAQ, TRAQ

Click on the link to learn more about the tree from OSU Extension: https://bygl.osu.edu/node/625