HONEYLOCUST AGROFORESTRY

 

Honeylocust Adaptability.  Honeylocust grows in a wide range of climates in the temperate and subtropical zones.  It is native to the southern three-quarters of the Mississippi River basin (USA) but is now found throughout the continental US as well as most temperate zone regions of Europe, Algeria, South Africa, New Zealand, and Australia.  Introductory trails have taken place in India, Bhutan, Pakistan, and Nepal.  Honeylocust is winter hardy to temperatures of -34 degrees centigrade.  It thrives in a variety of soils, although it grows poorly on shallow, gravely, or heavy clay soils.  It does well in alkaline soils and is somewhat tolerant to salinity.  Honeylocust grows best on soil with a pH of 6.0 to 8.0  It is drought-resistant (the natural range includes areas with 51 cm {20 inches} annual precipitation) and can survive severe storms.  Honeylocust flowers in early May to late June when leaves are nearly full grown.  Late spring frosts can damage leaves and flowers when trees are planted in severe frost pockets. 

 

Pod Production for Animal Fodder.  Although incomplete, available data on honeylocust pod production indicate high yields in some cases, and considerable variation between southern and northern region of the temperate zone.  Several cultivars have been selected for high pod yields and pods with high sugar contents.  Annual yields of 180 kg {396 pounds} from individual mature trees have been reported from South Africa, New Zealand, and the US.  Ten-year-old trees grown in the southern US yielded 43 kg {96 pounds} per tree.  Honeylocust have produced considerably lower yields in the shorter growing seasons of the middle and northern USA.  Honeylocust is naturally heavily biennial. 

 

Depending on latitude, seeds ripen from mid-September to mid-October.  Mature pods drop gradually throughout the fall, permitting an extended period of livestock feeding. 

 

Pod Nutritional Value.  Honeylocust pods have a nutritional value between oats and barley.  The nutritional content of pods varies depending on growing conditions and cultivar.  A sugar content of 30 percent and digestible protein of 5 percent have been reported.  Sheep are able to digest the hard honeylocust seed.  Because cattle can not digest the honeylocust seed, pods must be ground for cattle to receive the full protein value.  Honeylocust pods have been fed successfully to sheep, cattle, and goats.

 

Honeylocust Leaf and Twig Fodder.  Honeylocust leaf and twig fodder tests high nutritionally in gross energy(kcal/g, calories/pound), sugars, mineral composition, and crude protein.  Leaf and twig fodder may be used to feed livestock on a cut-and-carry basis or browsed directly.

 


Agroforestry Tree Spacings.  Honeylocust can be planted on 5 to 10 meters squares {15x30 feet} in a pasture orchard (approximately 85 trees per hectare {33 tree per acre}), 3 to 10 meters {9-30 feet) along fencerows and riparian buffer strips, and .2 to .5 meters {2-20 inches} in alleycrop plantings.  Although honeylocust has a large taproot, it is not difficult to transplant.  Honeylocust has a broad flat-topped crown, and at maturity can reach 25 meters {82 feet) in height and .5 to 1 meter {20 to 40 inches} in diameter.

 

 

Understory Grass Production.  Honeylocust's open canopy produces a light shade, minimizing the negative effects on summer grass production.  Informal observations of field workers suggest that pasture grasses grow well under honeylocust; grasses and legumes grow right up to the trunk of the tree.  Late spring leaf-out and early leaf drop in the fall minimize shading during these seasons.  In addition, the tree's small leaflets are easily absorbed into pasture grasses during fall leafdrop.

 

Honeylocust Dioecious.  Honeylocust is polygamo-dioecious.  While staminate (male) flowers are not required for pod formation, they are desirable for complete pollination and full seed development.  One staminate tree for each 15-20 pistillate (female) trees is recommended.  Identification of staminate and pistillate trees grown from seed must wait until trees reach pod bearing age, usually between 5-7 years.  Pistillate and staminate trees of desirable cultivars can be produced by budding or grafting.

 

Nitrogen Fixation.  Honeylocust is a member of the leguminous family, but lacks the root nodules where bacteria symbiotically fix atmospheric nitrogen.  For this reason honeylocust was thought not to fix nitrogen.  Recent research at Yale University in the USA suggests that honeylocust does fix nitrogen directly in its roots without the formation of nodules.  Further research now being conducted will most likely confirm the ability of honeylocust to fix nitrogen although at lower levels than nodulating leguminous species.

 

Honeylocust Thorns and Seedlings.  Honeylocust normally present thorns (up to 14 inches) dangerous to humans, livestock, and tractor tires; however, thornless trees can be produced by grafting scion wood taken from the thornless upper branches of the desired cultivars.  Livestock and wildlife consuming pods and defecating the undigested seeds will distribute seeds in pastures.  Seedlings from thornless grafted trees will usually present thorns.  One-year-old seedlings present green and flexible thorns, and young seedlings are usually browsed by livestock.

 

Urban Shade Tree.  Because honeylocust has been planted widely as a temper­ate-zone urban shade tree, an extensive literature exists on propagation, planting, fertilization, and disease and insect control.  This literature is available to facilitate adoption of honeylocust in agroforestry settings.  Experience with concentrated plantings of honeylocust in cities indicates that honeylocust will suffer some insect and disease damage.

 

Economic Evaluation.  Pod production and nutritional data have been used to determine the economic viability of silvopastural honeylocust.  Sensitivity analysis was applied to account for different pod production levels and fertilizer costs.  Shadow prices were used to value the pods.  Depending on cost and production assumptions used, inter­nal rates of return from silvopastoral honeylocust with sheep range from 9% to 25%.

 

        Andy Wilson, Springtree Agroforestry Project

       268 Springtree Lane, Scottsville, VA 24590 USA.

         Email [awilson@pvcc.edu]  Tel: 434-286-3466.