Black Locust: A Michigan Invasive Tree

Black Locust flowers

Black Locust (Robinia pseudoacacia) is a medium size tree. Native south of Michigan, its range reaches into southern Ohio. Planted to the north because its wood is used for fence posts, tool handles, and wheel hubs. Trees planted in rows along the edge of a field often served as living fence posts. It spreads by seeds and can send out suckers, forming large stands.

Black locust leaves and spines
Black locust winter twigs

It is identified by its alternate, compound leaves that have entire (toothless) margins and twigs with a pair of spines at each node. Black Locust seedpods are smooth and resemble garden peapods. The racemes of white, fragrant flowers are pretty. Winter twigs have buds partly hidden under reddish-brown hairs.

Black locust seedpods and bark
Stand of Black locust along Lake Superior south shore

Black Locust occurs throughout the state. It is often seen in natural areas in southern Michigan and along the shores of the Great Lakes. Because of its suckering habit it out competes natives and can be challenging to eradicate.

 
Copyright 2021 by Donald Drife

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Alternate Trees Armed

Crataegus

Hawthorn

 

Hawthorn (Crataegus spp.) is a small tree with round reddish or brownish lateral buds. The thorns are sharp. Voss and Reznicek list 29 species in this genus from Michigan but many are only shrubs.

Gleditsia triacanthos

Honeylocust

 

 

Honeylocust (Gleditsia triacanthos) is a rare native in found in southern Michigan. It is planted widely including a thornless form (f. intermis). The twigs and trunk are armed with branched thorns. The terminal bud is absent and the lateral buds are hidden under the twig’s epidermis. Most trees will have a few seedpods that look like long, dark, flat, peapods (it is in the Fabaceae, Pea Family).

Malus coronaria

Wild Crab Apple

 

Wild Crab Apple (Malus coronaria), also called Sweet Crab, or American Crab is similar to Hawthorn. The buds are pointed and the thorns are blunt pointed. The thorns normally have leaf scars.

 

 

Robinia pseudoacacia

Black Locust

 

Black Locust (Robinia pseudoacacia) is not native to Michigan but widely planted and escaped. The terminal bud is absent and each lateral bud scar has a pair of stipular spines. The reddish buds are partially hidden by the epidermis.

 

Voss, Edward G. and Anton Reznicek. (2012). Field Manual of Michigan Flora. Ann Arbor: University of Michigan Press. (Crataegus on pp.811-819)
Copyright 2013 by Donald Drife

Webpage Michigan Nature Guy
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