black locust vs honey locust

Tanti Al Zember

4 min read

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27-12-2024

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Black Locust vs. Honey Locust: A Detailed Comparison

Choosing the right tree for your landscape requires careful consideration. Two species often causing confusion are the black locust ( Robinia pseudoacacia) and the honey locust (Gleditsia triacanthos). While both offer attractive features, they possess distinct characteristics that make them suitable for different applications. This article will delve into a detailed comparison, highlighting their differences and similarities, drawing upon information from scientific literature and adding practical insights for homeowners and landscapers.

I. Identifying Key Differences:

The most immediate difference lies in their thorns. This is where the names become particularly descriptive.

• Black Locust (Robinia pseudoacacia): Features stout, paired thorns at the base of the leaves. These thorns are formidable and can easily injure unsuspecting individuals. "They are typically found on younger stems and branches, becoming less prevalent on mature trees," according to research found on ScienceDirect (though specific citations would require access to the full database and its search functionality). This suggests pruning considerations for managing potential hazards, particularly near walkways or play areas. Mature black locusts may still retain some thorns, but their density is noticeably reduced.

• Honey Locust (Gleditsia triacanthos): Possesses a more complex thorn structure. Younger trees, especially, are densely armed with branched thorns, often clustered together forming formidable defenses. However, many thornless cultivars are widely available, making them a more attractive option for homeowners concerned about safety. The presence or absence of thorns should always be a primary consideration when selecting a honey locust for planting.

II. Leaf Structure and Appearance:

Both trees have pinnately compound leaves, meaning leaflets arranged along a central stem. However, subtle differences exist:

• Black Locust: Has 7–19 oval-shaped leaflets, generally arranged in an even number along each stem. The leaflets are a medium to dark green, turning yellowish-green in the fall. Their smooth texture further distinguishes them from the honey locust.

• Honey Locust: Displays a greater variation in leaflet number (often 10-30) and shape. Leaflets are more finely toothed and oblong compared to the black locust. The overall appearance is often described as more delicate and airy. Many cultivars have fern-like leaves, significantly enhancing their ornamental value.

III. Growth Habits and Size:

Understanding growth patterns is crucial for proper site selection.

• Black Locust: Known for its rapid growth, it can reach heights of 50-70 feet, with a somewhat irregular, spreading crown. It's remarkably adaptable, thriving in a variety of soil conditions and tolerating some drought. Its deep taproot system makes it very drought tolerant once established. However, this same root system can make transplanting older black locusts very difficult.

• Honey Locust: Also a fast-growing tree, but it can achieve even greater heights (up to 80 feet) with a more graceful, vase-shaped form in some cultivars. Like black locust, it adapts well to various soil types, though it prefers well-drained locations. This makes it a suitable option for many urban settings, though careful cultivar selection (thorns and size) is essential.

IV. Flowering and Fruiting:

The flowering and fruiting characteristics of both species are strikingly different:

• Black Locust: Produces fragrant, pendulous clusters of white flowers in late spring. These flowers are a valuable source of nectar for pollinators. The tree produces flat, bean-like pods that persist through winter and are a notable ornamental feature. These pods are not typically considered palatable to humans.

• Honey Locust: Features less conspicuous flowers, small and greenish-yellow, often clustered in inconspicuous racemes. The defining characteristic is its long, twisted, reddish-brown pods, which can be several inches long. Some cultivars produce seedless pods, eliminating the mess associated with fallen seed pods. These pods can persist through the winter, providing winter interest but also potentially becoming a nuisance.

V. Wood Properties and Uses:

Both species yield valuable timber, albeit with distinct properties:

• Black Locust: Celebrated for its exceptional durability and rot resistance. Historically used for fence posts, railroad ties, and shipbuilding due to its exceptional strength and density. Today, it is still highly valued for outdoor applications where durability is paramount.

• Honey Locust: Also a durable wood, but generally considered less resistant to rot than black locust. It finds use in furniture making, flooring, and other interior applications.

VI. Pest and Disease Resistance:

While both trees are generally considered hardy, they can suffer from certain pests and diseases:

• Black Locust: Susceptible to locust borer infestations, which can significantly weaken or kill trees. Proper tree care and monitoring are essential for preventing severe infestations.

• Honey Locust: Can be susceptible to various fungal diseases. Good air circulation and avoidance of overwatering help minimize the risk of fungal infections.

VII. Landscape Applications:

The choice between black locust and honey locust depends on specific landscaping needs:

• Black Locust: Suitable for naturalized settings, windbreaks, or areas requiring a tough, durable tree. Its aggressive root system requires careful placement away from buildings or underground utilities. The thorns necessitate consideration of pedestrian safety.

• Honey Locust: A more versatile option, particularly the thornless cultivars. Excellent for larger landscapes, parks, or street plantings. Its faster growth and more graceful form make it a popular choice for ornamental purposes. Cultivars with seedless pods reduce the amount of mess and cleanup required.

VIII. Conclusion:

The selection between black locust and honey locust should be carefully considered based on your specific landscaping goals and site conditions. While both species offer unique advantages, the presence or absence of thorns, growth habits, and pest resistance should be primary factors in your decision. Researching specific cultivars of each species is highly recommended to find the perfect tree for your needs. Remember to consult local arborists for advice tailored to your region's climate and soil conditions. Careful planning ensures that your chosen tree will thrive and provide years of beauty and benefit to your landscape.