The locust tree is the quintessential shade tree known for its attractive form, great-looking fall foliage, and highly impressive leaves. Anyone interested in growing trees can make it part of their plant or tree collection, allowing them to witness a spreading canopy capable of providing a nice spot with shade.
Yes, there is a problem with its thorns being poisonous but not all varieties of this tree are toxic. Many say that the only locust trees that contain the toxic and poisonous substance known as toxalbumin are those that belong to the black locusts.
This article explains more about the amazing locust trees and how to deal with their thorns.
In This Article
What are Locust Trees?
Locust trees refer to rapidly growing flowering trees that belong to the pea family and a group of flowering plants known as Fabaceae. It is famous for its ability to grow large clusters or groups of pea-like flowers that tend to bloom during the spring. Once the flowers bloom, long pods will follow.
The locust also falls under hardy trees famous for their durable and hard wood, colorful fall foliage, and sweet-smelling flowers for spring. Several of its varieties come with long, fierce, and sharp thorns that tend to grow in pairs. You can see these thorns along the tree’s lower branches and their trunk. There are also some thornless varieties.
Two of the most famous types are the honey locust trees (Gleditsia triacanthos) and the black locust trees (Robinia pseudoacacia). Both of them are native to North America. If you wish to grow any locust varieties, then you will be glad to know that it is easy to grow one as they can adapt to various street and lawn conditions.
The Two Major Types of Locust Trees
Considered among nature’s jewels and treasures, the locust tree continues to leave a good impression with its different types and varieties. The ability of this tree to adapt well to various conditions and suit different needs and gardens is also one reason why it is one of the top choices of those who intend to grow their own trees.
Generally, you can find two major locust trees: the black locust tree with the scientific name Robinia pseudoacacia and the honey locust tree with the scientific name Gleditsia triacanthos. Both are known for being endemic in the entire region of North America.
You can differentiate between these two major types of locust trees by checking out the thorns at the branches and barks. Most varieties of black locust tree come with thorns while the varieties that fall under honey locust trees are often thornless.
You can also differentiate the two based on their benefits and uses and their identifying features and characteristics that you will learn in the next parts of this article.
Honey Locust Tree
A common type of tree well-loved by gardeners in different parts of the world, the honey locust trees continue to impress because of their elegant nature. It looks elegant as it features arching leaves that radiate in clumps starting from a central point. This makes them slightly look like rosettes.
It has leaves that begin to look light green once the spring season comes then slowly become darker. The leaves will show an impressively rich shade of bright yellow when the fall comes. This is very nice to look at and can add a more energized look to your garden.
Another impressive fact about the honey locust tree is that it has a thick canopy that aids in blocking sunlight. This makes it a perfect choice if you intend to make a restful and relaxing part of your garden with a nice shade.
It also has thin yet elegant-looking branches and a gray trunk with huge purple thorns covering it. The presence of these thorns makes it kind of impossible to climb the tree but they also make this locust tree variety quirky yet attractive.
Honey locusts also have inflorescences that are not that rich and thick, making them different from other varieties. However, all of them are aesthetically pleasing and boast of their nice scents. They also have pods that tend to bend and curl a bit. Expect them to look green at first then become red and lastly, brown.
Another reason to love the honey locust trees is that they are stand-alone or independent, making them incredible choices for all kinds of gardens. It can attract attention, especially during the spring and late fall seasons. Despite being an independent tree, growing this variety with other trees is also fine provided they are in big compositions.
If you are planning to grow honey locust trees, take note of the following:
- Light: Full sun
- Soil: Most soil types, including alkaline, acidic, and neutral – It can thrive in salty soil, too, and can tolerate light drought and a bit of flooding.
- Hardiness: USDA zones 2-9
You also have to consider its size upon reaching maturity before growing it, so you can provide it with the right amount of space for growth. Expect it to grow to around 30 to 70 feet tall. As for its spread, it could be anywhere from 9 to 23 meters.
Uses of the Honey Locust Trees
Classified as hardwoods, honey locust trees are definitely among the best providers of wood. Note, though, that aside from the locust wood, it can also supply other benefits – among which are the following:
These are among those locusts capable of supplying people with food. It has edible seed pods known for their chewy and sweet pulps. You can use these pulps in making traditional cuisines and recipes and in preparing medicines.
Presently, you can see these pulps being used in producing herbal tea. Some also use the pulps of the seed pod to ferment beer. Many also harvest entire seed pods to create livestock feed.
Good for landscaping
Honey locust is also commonly used in landscaping. The main reason is its effectiveness in providing shade while controlling erosion. Note, though, that it also tends to grow excessively, which is why some regions still consider it highly invasive.
One more thing that honey locusts can do for you is supplying you with highly durable wood and timber. You can cultivate it to craft furniture in carpentry, which makes it different from the black locust.
Black Locust Tree
Also called Robinia Pseudoacacia, the black locust tree (false acacia) is also another of the most common variety or type of locust tree. This is a very distinctive and unique variety that the sweet scent of its flowers will definitely invite pollinators and humans to your garden.
The all-encompassing fragrance of its flowers is the reason behind its popularity in various gardens and parks worldwide. Combine that with the decorative shape of its branches, trunk, and foliage, and this tree will surely add a more aesthetic appeal to your garden.
There is a high chance for its trunk to become really large. Expect it to grow straight then branch off eventually with elegance and balance to form big fronds of foliage capable of arching and drooping once the generous and rich flowers with nice scents start enveloping them with the shade of white.
Many are also impressed with the bright-green leaves of this tree. It mixes well with the black locust’s white racemes or inflorescences, resulting in the nicely set shape of the tree’s branches in reddish black.
Compared to other locust tree varieties, the pods of the black locusts are smaller. Despite that, they still have this unique decorative trait of producing a huge number, especially upon turning bright red in color and then eventually, brown.
One more distinctive feature of the black locusts is their oblong crown, which you can see atop its straight trunk. This can give the tree an oriental or Japanese appeal despite being a native plant in the US.
The black locust tree is also very appealing that everyone will notice its presence in a park or garden. Just like the honey locust, it also looks elegant and can stand alone. You can choose to use it for small wooded or shady areas or as a focal point on your large lawn.
It is a strong tree that is adaptable and easy to grow while having the ability to resist various pests, insects, and diseases. As a guide in growing this famous locust tree, take note of the following:
- Light: Full sun
- Soil: All types of soil, sand, chalk, loam, and clay – The pH level should be a bit acidic or alkaline. It thrives at a neutral level, too. The black locusts can also fairly tolerate drought, though, you should still avoid exposing it to excessive flooding and water. It has to be in a soil that drains well.
- Hardiness: USDA zones 4-9
As for its size, expect this tree to grow around 30 to 50 feet high. It can also spread to around 20 to 35 feet.
Uses of Black Locust
Overall, the black locust is also a fantastic hardwood tree capable of growing thick and tall. With that characteristic, you will definitely be able to find it useful for the following purposes:
You will love the ability of black locust trees to produce and provide highly durable and quality timber. You can use this timber to manufacture fences and perform other services when it comes to carpentry.
The wood of black locusts is also very sturdy. This makes it extremely difficult to burn, which is a good thing for anyone in search of a good source of firewood.
Do you know that black locust trees are also effective in producing honey? This is one of its most endearing qualities. This tree is capable of blooming dense groups or clusters of flowers capable of attracting bees. It is the main reason why you can see this tree being planted in those places that need solid and robust production of honey.
How to Identify a Locust Tree?
Locust tree identification during the spring is possible by checking out the presence of pendant clusters of sweet and fragrant pea-shaped flowers often in the shades of pink and white. Also, observe if there are forked, straight, or sharp spines, which also indicate locusts.
You can also distinguish them with the help of their pinnately and feathery compound leaves. Note that various locust tree species also grow healthily in the wild, especially in North America. You will have an easier time distinguishing them by checking out their size, flower color, seed pod color, and shape, and the thorns’ location and structures.
Identifying the Honey Locust
For the honey locust, you can identify them as many consider them tall locust species. While there are several thornless cultivars and varieties of honey locusts, note that the ones that have thorns are also considered the fiercest.
There are varieties of the tall honey locust with larger branches and trunks capable of bearing branched and stout thorns that can reach up to 20-inch in length. If you are not careful, it may lead to serious injuries. Choose the thornless cultivars if you love this locust tree because of its flowers, not the spikes and thorns.
You can also identify the honey locust flowers with their greenish-yellow shade instead of the pink or white one and are fairly insignificant when you compare them to the other locust trees with showy flowers. Honey locust can also produce the heaviest and largest pods – around ten to eighteen inches long and one inch wide.
You will also notice their twisted pods in dark brown. There are also 1-inch individual leaflets that you can find in their leaves. The pinnately compound leaves are also usually around seven to eight inches long.
Identifying Black Locust
As for the black locust trees, you can easily identify them through their fragrant flowers that are often around an inch long and appear in pendant clusters during the late spring. The tree also features dark red to black and leathery seed pods that are around two to four inches in length.
Another distinguishing feature of the black locust is a pair of sharp and short spines where you can see its leaf being connected to the stem. It has a trunk and branches with stout spines that are usually branched, though not as big as the honey locust’s spines.
The black locust is kind of invasive and features twenty-one leaflets less than two inches long.
Other Famous Types and Varieties
While the honey locust and the black locust trees are the major types of locust trees worldwide, they also have a few varieties and species that gained positive attention under them. Among these locust varieties are the following:
Imperial Honey Locust Tree
If you are in search of a thornless locust tree, the Imperial honey locust is ideal for you. It has no thorns and features a large canopy. The Imperial honey locust tree is a good choice for those looking for aesthetic shade trees perfect for streets and gardens.
Overall, you will notice the Imperial honey locust showing off its ferny structure that has a tinge of yellow green. It is also a very strong and solid tree, thanks to its ability to withstand various soil and environmental conditions. You can even expect it to resist saline conditions, high winds, and insufficient water.
This tree also shows tiny clusters of beautiful florets in greenish-white that tend to bloom during late spring to early summer. It also has bright green and feather-like leaves. To grow this locust tree variety, ensure to provide it with full sunlight and moist but well-drained soil.
Shademaster Honey Locust Tree
This tree is distinguishable because it does not have thorns plus it grows really fast. It even has an average growth of 50 feet. It does not bear fruits, which is why it does not come with seed pods.
This is also the reason why the Shademaster honey locust tree is classified as an easy-to-maintain locust. It showcases green foliage during the spring season that you can expect to turn yellow once the fall comes. It also has mildly scented yellow flowers that bloom beginning from spring to summer.
Thornless Honey Locust
This variety is also known for its scientific name Gleditsia triacanthos form inermis. It is a good choice if you are in search of a thornless honey locust tree variety. It derived its name from the fact that it indeed has no thorns at the twigs and barks, making it distinguishable from other honey locust trees.
This thornless honey locust tree is also famous for being really adaptive and durable. It can even tolerate salt and drought. It features deep green ferny leaves during the spring that become golden yellow once the fall comes. You can often find the Gleditsia triacanthos form inermis or this thornless locust tree in suburban landscapes and cities.
Sunburst Honey Locust
This variety is a mid-west US native capable of growing in cold and moist locations. It is also one of the honey locust varieties capable of growing really rapidly. It grows fast as a shade tree and follows an arching habit, allowing it to showcase a shade of around 30 to 35 feet and a height of around 30 to 50 feet.
You will also notice the leaf gaps in this variety that provide the plants in any lawn dappled light. The sunburst honey locust tree also features bright yellow leaves that tend to come out during the spring and then turn into pale green once the fall comes.
When planning to grow the sunburst honey locust tree, remember that it requires deep watering and pruning during the winter. Overall, it is one of the nicest accent and shade trees with the ability to resist deer and various diseases.
Skyline Honey Locust
The highly distinctive ferny structure with up to 45-feet growth and 25-feet spread of the skyline honey locust tree is one of the things that makes it so appealing to many people. It is unique in that it grows upright, which is why you can commonly find it in streets and parks.
Even better about the skyline honey locust tree is that it does not require much care and maintenance. The only things it needs are winter pruning and sufficient sunlight. It can tolerate various soil pH levels and features yellow-green flowers and chewy and sweet seeds. Be extra careful, as skyline honey locust also has a thorny trunk.
Also called Robinia pseudoacacia ‘Purple Robe’, this is one of the locust tree varieties that fall under the shade tree classification and known for its ability to withstand even those inferior growing conditions. Note, though, that the purple robe locust tree has this invasive nature, which is why it is not ideal for household lawns.
The purple robe locust tree is also very thorny and has relatively weaker wood than the others. It is crucial to prune this tree during the summer and fall to ensure that it retains its pyramid-like shape.
New Mexico Locust Tree
With its scientific name Robinia neomexicana, the New Mexico locust tree is also famous as a native plant in Southwest US. One can choose to cultivate it as a tree or a shrub. This will depend on the kind of soil it will grow and the specific amount of sun it would most likely receive.
Because of its thick and large branches, you can also easily distinguish the New Mexico locust tree. It also has masses of flowers that you can expect to bloom starting from the spring season to summer. The New Mexico locust tree also boasts an average growth of 10 feet.
Bristly Locust Tree
The bristly locust tree is also otherwise known as the moss locust and the rose acacia. It falls under the deciduous trees or deciduous shrubs classification and has an average growth of 8 feet.
One thing to note about the rose acacia or bristly locust tree is that it is an aggressive grower, which is why it is classified as an invasive locust shrub in some places, like Michigan, Ohio, and Washington. This tree has bristly stems, which is the reason behind its name.
It also has fragrant white flowers capable of attracting insects, including bees. Expect the bristly locust trees to thrive well in moist and loamy soil with high salt levels. It is also effective in terms of erosion control.
Frisia Black Locust
This black locust tree variety is famous for growing really fast. It can go at around 30 to 50 tall and 30 to 40 spread. The growth of this tree is also mainly upright and features leaf gaps capable of casting sufficient lights so other lawn plants can grow.
Since it is a black locust variety, you will notice its thorny shoots that are in the shade of deep red. As for its foliage, you can expect to see it in rich green during the spring and turning into yellow green then golden yellow in the summer and fall, respectively. This is also a drought-tolerant tree capable of blooming fragrant white flowers.
Are Locust Tree Thorns Poisonous?
While many say that locust trees are poisonous, you should still remember that not all of them are toxic and poisonous. The only one that has a toxic substance known as toxalbumin is black lotus.
Ingesting it may have fatal effects, though, it has been discovered that it is rare for people to get poisoned because of coming in direct contact with this tree. One thing to take note of about its toxic part is that it is concentrated on the leaves, bark, and branches.
Upon ingestion, the effects are vomiting, diarrhea, and stomach pain in pets, children, and livestock.
How to Control Locust Trees?
Aside from the possibility of the thorns poisoning those who come in contact with them (though, this is just rare), the tree is also kind of invasive, so learning how to control its spread and rapid growth is also sometimes necessary. Note, though, that controlling various locust species is a bit difficult.
One reason is its rapid growth. Black locust trees, for instance, spread really fast through root suckers and self-seeding. An effective way to control it is to identify the root suckers immediately and then get rid of them equally.
In several cases, you have to perform the treatment method again, regardless of what it is, to keep the tree under control. You can also control black and honey locusts by cutting back these trees each growing season.
Cut new growths and stems and be patient as you may have to do them several times throughout the year. If you want to prevent the sprouting of new trees, you can also spread hay over the entire area.
Frequently Asked Questions (FAQs)
What is a locust leaf?
As the name suggests, it refers to the leaf of a locust tree, which is often pinnately shaped while being feather-like. Depending on the species, the locust leaf could be light green. There could also be dark green leaves. It will then turn into bright yellow once the fall comes.
Can you eat locusts’ blooms?
Yes. The blooms of the locusts that refer to their flowers are edible. You can pick them but be extra careful if the tree has thorns. Once picked, you can put the blooms or flowers in a mixture composed of water, lemons, and sugar then allow it to sit overnight before eating.
What is the most common locust?
The most common and popular among the many locust varieties are the honey locust (Gleditsia triacanthos) and black locust or Robinia pseudoacacia. The two are deciduous trees that also work well in the landscape.
How often do locust trees bloom?
Most locust trees bloom every year provided freezing did not kill them. You will also notice the black locust blooming prolifically even if some of its varieties don’t bloom annually.
What can you do with the locust pods?
You can use the seed pods of locust trees as fodder for your livestock. They are also good for medicinal purposes.
Are the pods of the locust tree edible?
Locust trees have pods with pulp inside. The pulp on the pods is the one edible and can be consumed by livestock and wildlife. Note, though, that you have to pick the honey locust tree for this as the pods of black locust are toxic.
Are honey locust trees messy?
In general, honey locust trees are non-messy. Note, though, that it also depends on how you define messy. If you have the seedless and thornless variety of honey locusts, it is not that messy as the debris it drops over a short period every year is easy to clean.
It is most likely messy if the trees are those that continuously drop twigs, large leaves, and nuts.