When is a Locust not a Locust?
In 2013, the arboretum's curator Lacey Anderson collected seed pods of a thorny locust from the side of Old Mooringsport Road north of Shreveport. The seeds germinated in the campus greenhouse under Dr. Ed Leuck's supervision, and a seedling was planted in the arboretum in 2015. The tree pictured below is about four years old. Dr. Ed Leuck had previously collected and planted a Black Locust in 1997, but the tree was displaced by the construction of the Fitness Center and it later died.
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| Locust tree approximately 4 years old |
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| This young locust tree has required significant pruning to develop a single trunk. Several long, spindly branches haven been removed over the past several months. |
The initial identification of this tree as Black Locust (
Robinia pseudoacacia) was made on the basis of the seed pods and thorns of the donor plant. As the tree has grown up, some doubts have entered the mind. Let's examine the evidence.
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Left pane: Robinia pseudoacacia diagram
Right pane: photograph of the specimen | |
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The
Petrides reference volume states that
Robinia pseudoacacia has opposite thorns of between half-inch to one-inch length, while our specimen has single thorns of two-inch length.
Robinia pseudoacacia has around thirteen leaflets with a single terminal leaflet, while our specimen has sixteen to twenty leaflets and a terminal pair.
Robinia pseudoacacia has smaller flat seed pods while the parent tree had large, twisted seed pods.
Thus, the arboretum's specimen is a
Gleditsia, probably the Honey Locust (
Gleditsia triacanthos). There is a possibility that it may be a hybrid between the Honey Locust and the similar Water Locust (
Gleditsia aquatica) but the tree will have to grow up more before we can make this determination.
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| Thorns of the Honey Locust are fearsome and longer than an inch. |
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| Cultivars have been selected for fewer thorns, but this wild strain is very concerned with self-preservation. |
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| The base of the tree is also heavily thorned, discouraging climbers and nibblers. |
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| This young tree has not yet developed bark with a lot of character. It might be called scaly. |
