The term “locust” can apply to several different species of trees with legume-like seed pods.
Locust trees are from the Fabaceae (legumes or pea family) family native to North America. Different locust trees are classified as part of the Gleditsia or Robinia genera. Meaning locusts can be trees or shrubs.
The most popular types of locust trees in North America are called black locust and honey locust.
In this article you’ll find all you need to know about their uses, popular varieties and related planting processes.
The Victorians even believed there were secret meanings behind locust trees and other flower and tree species.
Honey Locust Trees (gleditsia triacanthos)
Among landscaping trees, honey locust has become very common, and with good reason. The honey locust (Gleditsia triacanthos) is a fast-growing tree.
Honey locusts, or Gleditsia triacanthos, are part of the Gleditsia genus. They’re also referred to as ‘thorny honeylocust’ or ‘thorny locust’.
The honey locust is a deciduous tree, meaning it tends to shed its leaves and flower petals. It’s native to the central North American region and can be found in soils along river valleys.
Honey locusts are hardy, strong and commonly able to tolerate wind storms, ice, soil compacting foot traffic, and pollution. They also grow fast – about 20 feet high in their first decade – and eventually up to 70 feet.
They have beautiful gray-brown barks and tiny, oval leaves that turn yellow in the fall. Most of the different varieties also produce pods as fruits with edible pulp inside them.
Search for them by their scientific name – gleditsia triacanthos – and create a beautiful landscape view for your garden.
How Many Types of Locust Trees Are There?
The New Mexico Locust
The New Mexico locust tree, or Robinia neomexicana, isn’t a Mexican tree, contrary to its name. It’s actually found mostly in the Southwest of the United States.
This locust tree species can grow into a tree or a shrub and it reaches heights of about 10 feet with beautiful purple branches and flower batches that bloom in spring and summer.
The Imperial Honey Locust
This type of honey locust, also known as Impcole, grows to about 35 feet high.
It has yellow-green flowers and feathery leaves that almost look like ferns. The leaves are green during spring and summer, yellow in the fall and shed in winter.
The Shademaster Honey Locust
The Shademaster honey locust tree has no thorns and grows faster than most locust trees. Reaching heights of 50 feet and upwards.
One advantage of growing Shademasters is that they don’t produce fruits. Meaning they’re easier to maintain than other locust trees.
The leaves of a Shademaster are green, though they turn yellow in the fall. The flowers are yellow in color, small in size, and produce a delightful aroma.
The Skyline Honey Locust
The skyline honey locust, or Skycole, has beautiful leaves in pyramid-shaped ferns. Growing to heights of 45 feet and spreads of about 35 feet.
Like the Shademaster, the skyline doesn’t produce any fruits and it doesn’t have thorns.
The Bristly Locust
This honey locust, also known as Robinia hispida or ‘moss shrub’, is a shrub that grows up to 8 feet. It produces captivating pink flowers and green leaves.
Bristly locusts can spread and develop into invasive plants in the following states:
Uses of Honey Locusts
These plants are cultivated for a variety of purposes which include:
Honey locusts provide reliable wood used in building constructions and even furniture. Though its wood isn’t the main reason why it’s widely planted.
Food and Medicine
Honest locusts have edible seed pods, unlike black locusts’ pods which are harmful.
The pulp in honey locust seed pods can be used as food or even traditional, Native American medicine. Other consumption purposes of the honey locust include:
- Making tea
- Feeding livestock and wildlife, being from the pea family
- Producing beer
It should be noted, however, that a honey locust tree doesn’t play any part in producing actual honey. Its name has more to do with the pleasant taste of its pulp than anything else.
The main reasons why they’re cultivated are because of landscaping aspects. Though the over-planting of this tree has presented some problems, such as:
- A greater number of pests and tree diseases.
- Barrier creations along rivers which block animals from reaching water streams.
- Invasion of farmlands, preventing crops from growing.
Black Locust Robinia Pseudoacacia Tree
Black locusts, or Robinia pseudoacacia, belong to the Robinia genus. They’re fast-growing, strong trees, found in the woodland areas along stream banks of the U.S.A.
The black locust robinia tree can tolerate poor soil, drought, pollution, and even salt. Growing up to 70 feet tall and 30 feet wide in areas with lots of sun and moderate moisture levels.
Black locust leaves are generally blue-green, small and oval, with short sharp thorns. They’re covered in blossoms in spring, before turning yellow and dropping in the fall.
Although, this does depend on the different varieties of locusts.
Popular Black Locust Varieties
The Twisty Baby Black Locust Tree
This Robinia pseudoacacia cultivar, better known as ‘Lace Lady’, can be cultivated as a tree or a shrub. It can reach heights of 20 feet tall when planted in the ground and 5 feet when planted in a gardening pot.
The name ‘Twisty Baby’ comes from the fact that this tree’s branches contort and spiral in an odd way. You can exaggerate the twist on this variety by pruning it back in the cold winter season.
The Purple Robe Black Locust Tree
This black locust tree variety is incredibly captivating to look at. Its leaves change depending on their stages:
- Blooming: green leaves with subtle purple hues.
- Fully formed: distinctly bronze-colored leaves.
The flowers on this tree are just as stunning and contrast well with the leaves in pink and purple shades.
The Frisia Black Locust Tree
This lovely cultivar is a bit smaller than other locusts with heights of up to 40 feet and spreads of 25 feet. But its beauty makes it ideal for decorative purposes. It has vivid yellow foliage that can at times turn into shades of lime green.
Uses of Black Locust Tree
Known for strength and durability, black locusts appealed to pioneers for different reasons. These include:
Black locusts are considered hardwood trees, meaning they are denser than others.
“Hardwood trees are equipped with xylem vessels, which are used to carry and distribute water through the trees. Their cell walls are lined with lignin, an extremely tough material that is responsible for the tree’s hardness. This stands in stark contrast to softwood, where the vascular structure is not unlike a cluster of drinking straws.” — Maximum Yield
This makes black locust trees perfect as timber to build structures with and make fences.
Its fast-growing aspect is a plus and also means that the black locust is cultivated a lot.
A black locust’s high density makes it hard to cut through but also more durable as firewood. It takes a long time to burn through and provides greater efficiency than other trees.
The flowers on black locusts blossom lavishly, creating broad batches of bee-attracting blooms.
“These flowers are attractive to bees and provide a good source of nectar. Therefore, black locust trees are planted in regions where honeybees are operating to help them with their honey production.” — Green and Vibrant
Ornamenting and Shading
The heavy blossoming of a black locust’s flowers also makes them ideal as an ornamental tree. Its flowers give out a wonderful fragrance and are white, pink, or purple in color. And the batches of flowers dangle from the tree and measure between 4 to 10 inches.
Black locusts’ branches are brittle and tend to grow sporadically, creating gaps in-between. Meaning, they provide the perfect shade that plants growing below them need.
Problems with Locust Trees
In some areas, cankers and root collar rot are serious problems for honey locust trees.
Cankers first appear as flattened or discolored surfaces on the branches and trunk of the tree. Over time, cankers can spread and completely girdle the tree, causing tree death. Cankers also cause slow growth, yellowing leaves or sparse leaves.
Root collar rot is a similar disorder that appears at the base of the tree as a yellow or white area.
To prevent canker and root collar rot, keep trees vigorous and healthy:
- Water during dry periods, especially if the tree isn’t in an irrigated lawn.
- Be careful when mowing around the tree not to injure the trunk because injuries provide an entry point for these diseases.
- Prune out infected branches, cutting limbs at least 12 inches below the infected area.
- Disinfect pruning tools between cuts with a solution of 1 part bleach to 10 parts water.
How to Plant and Grow Locust Trees
Plant locust trees in full sun, spaced at least 30 feet from other trees. Water trees frequently the first year as the roots become established. Older trees rarely need additional irrigation or fertilizing, especially if they are in an irrigated, fertilized lawn.
Before you plant locust tree seeds, prepare them first by:
- Boiling enough water (3 to 4 times the volume of the seeds).
- Allowing the water to cool for 1 minute.
- Putting the seeds into the hot water container.
- Letting the water cool until it reaches room temperature.
- Removing the seeds from the container once they’ve swollen up to 3 times their size.
- Planting your locust tree seeds as soon as they’ve been removed.
Planting and Caring
Planting locust trees requires:
- A vast field to cultivate them and provide enough space.
- Soil that’s been conditioned with a mix of cottonseed meal and powdered gypsum.
- Lots of sun for them to grow in.
- The right time of year (it’s best to plant in spring or summer and avoid colder seasons).
- Adequate drainage for the vast amounts of water you’ll use.
Locust trees need to be watered intensively in the beginning but avoid waterlogging. As your trees grow, they’ll need less and less water but that doesn’t mean you can neglect them. You should prune them on a regular basis for proper growth by removing their dead branches.
Learn More About Gardening
Planting locust trees is often a great idea because of their many purposes listed above. But there’s a lot more you could be doing with your gardens to make it thrive.
- How to Plant and Take Care of Your Honey Locust Tree from Utah State University Extension
- Black Locust: A Multi-Purpose Tree Species for Temperate Climates from Purdue University
- This YouTube video teaches more about the locust tree.
The Gardening Channel helps you get your dream garden by providing advice on how to garden.
Learn more about great organic gardening ideas and tips. You’ll discover something new whether you’re a gardening beginner or a seasoned pro. Pun intended.
“Locust Trees: Varieties and Growing Guide” was first posted here