There are a wide variety of non-native invasive plant species that have taken hold in Madison County. These plants cause harm to the environment, as well as potential harm to human, animal, and plant health in the preexisting environment. Some of these damages can be caused by overtaking beneficial native plants in the ecosystem, act as vectors for diseases and other invasive species, such as invasive insects, and are unhealthy or potentially toxic to native animals. In this series, we will discuss identification and control of these prevalent invasive plants.

Identifying Tree-of-Heaven

Tree-of-Heaven (scientific name Ailanthus altissima) is a deciduous tree species that originated in China, and has since spread across thirty continental US states and Hawaii. It is a small to medium-sized tree species, growing from about 40 feet to 80 feet at maturity, and spanning about 15 feet to 30 feet wide. The leaves of this tree are the best way to identify it, as it has large, alternate, compound leaves containing anywhere from 10 to 40 leaflets along the leaf stem. Each leaflet has a glandular, notched base with 1 to 3 serrations on those lower margins toward the base of the leaflet. This species is often confused with native plant species like sumac (Rhus spp.) and black walnut (Juglans nigra). A good way to determine if the species you are looking at is Tree-of-Heaven is by crushing the leaves. When crushed, their leaves produce a foul smell, sometimes described as a “burnt peanut butter” scent. 

Tree-of-Heaven is covered in smooth gray bark that begins to crack along the trunk as it ages, with coarse-grained, weak softwood that is a creamy white to light brown in color when cut. The stems of this invasive species are stout and covered in fine hairs, appearing as a light chestnut brown in color. The stems may also produce an unpleasant scent when broken, similar to the smell when the leaves are crushed. Flowers will bloom on the Tree-of-Heaven around mid-summer (July to August), and will bloom in panicles, which are branched flower clusters, at the ends of the branches. The flowers range in color from a coppery-brown color to a yellow-gold color to a yellowish green. The fruiting bodies containing the seeds are called samaras, and appear as a papery wing-like sheath that is slightly twisted or curled.  

The Tree-of-Heaven is also a known host for other invasive species, most notably the Spotted Lanternfly. The Spotted Lanternfly was first discovered in the US in eastern Pennsylvania in 2014, and has since spread throughout several other east-coast states including New York, Delaware, Virginia, Connecticut, Maryland, and several others, and was spotted in North Carolina for the first time in June 2022. This insect is a threat to agricultural and ornamental plants, as well as being a nuisance pest. The most affected crop when Spotted Lanternfly is present are grapevines, which can cause vineyards to see up to a 90% reduction in fruit yield. If infestations around these vineyards are heavy, present grapevines could be killed outright, and could disrupt or drive customers away from agritourism events, such as tours. Other agricultural crops that are affected by the presence of Spotted Lanternflies include hops, fruit trees (including apples, plums, cherries, apricots, and peaches), and many ornamental plants that could be used in landscaping. As a nuisance pest, these insects can cause problems for homeowners, businesses, tourism, and outdoor experiences, even those like eating in outdoor spaces at a restaurant. These insects are almost social, unafraid of humans, and because of this they can be very aggravating as they fly in crowded areas and may fly right in people’s faces. More information on the Spotted Lanternfly can be found linked here, and if you suspect you may have seen one, please take a photo and report it to NCDA&CS using this link. 

How It Spreads

The Tree-of-Heaven is an extremely prolific invasive plant species that is able to live in a wide variety of environments that many other species would not be able to survive or thrive in. The Tree-of-Heaven can survive in full sun and partial shade environments, and can live in a wide variety of soil textures and soil pH levels, including sandy, silty or loamy, clay, and even rocky soils with acidic, neutral, or basic pH levels. Due to its tolerance of even poor quality soils, Tree-of-Heaven thrives in urban and natural environments, and has even been known to displace native species, and grow between the cracks in concrete and pavement in urban areas. 

A single Tree-of-Heaven can produce several hundred-thousand of the samara-type seeds a year, which can be carried great distances away from the parent plant on the wind. The Tree-of-Heaven is also allelopathic, which means it creates a chemical that prevents other plants from growing in its vicinity. This damages native ecosystems and populations of more desirable plants, as well as contributing to the spread of this invasive species in the dense thickets it prefers to form. Roadways also help this invasive species travel far distances and spread from place to place, and the Tree-of-Heaven has taken over roadside areas throughout the mountains and piedmont of North Carolina. 

Controlling Tree-of-Heaven

Tree-of-Heaven is a difficult invasive plant species to control once it has established itself in an area. Your first main target when trying to control this invasive plant species is to target large, female fruit-bearing trees to attempt to reduce the spread of Tree-of-Heaven through its papery winged seeds. When the soil is moist, it is possible to hand-pull young seedlings that are beginning to sprout, but only if the diameter of these seedlings is half-an-inch in diameter or less. If attempting this, care must be taken to remove the entirety of the seedling, or those remaining pieces of root system can regrow into seedlings again. Attempts to cut down a Tree-of-Heaven often result in the root system redirecting its nutrients into growing root suckers and sprouts to take hold in the environment again. Because of this, Chemical control is most effective in removing Tree-of-Heaven. 

When a thicket of Tree-of-Heaven is present, it is recommended to apply a 4 percent glyphosate solution mixed with a 0.5 percent non-ionic surfactant to help ensure that the chemical sticks to the surface of the plant when applied as a foliar spray, or a spray over the leaf surface. Another, even more successful option of control is the use of 1.0 ounce of metsulfuron in 100 gallons of water mixed with a 0.5 percent non-ionic surfactant. This mix of solution can cover approximately an acre of Tree-of-Heaven thicket infested land. The use of foliar applications such as this have the potential of harming other surrounding plants, so if there is not a thicket or large infestation present, it may be best to consider more target options (see below)

Large trees are best controlled using the cut-stump method of chemical control. To do this method, the Tree-of-Heaven must be cut within six inches of the ground, and the freshly cut stump must be immediately sprayed with a 50 percent triclopyr solution over the newly exposed stump surface, and down the sides of the stump. When using this method, the freshly cut stump must be sprayed within the first three minutes of being cut to be most effective due to turgor pressure within the trunk of the tree. Turgor pressure is caused by the pressure of water within the plant cells that allows the plant to keep its upright and rigid structure, as well as aiding in the flow of nutrients across the expanse of the plant, from the tips of the leaves to the ends of the roots underground. The lingering presence of this turgor pressure after the Tree-of-Heaven has been cut helps with plant absorption of the herbicide used to control this invasive species. This act of spraying after the trunk is cut must also be done quickly due to the fact that plants have the potential to scab over injuries to protect themselves. This can prevent absorption of the herbicide, and will prevent control of the Tree-of-Heaven root system. Without the control of this root system, it will direct energy to new sprouts to begin growing again. This cut-stump method is best used between summer and early fall, when the plants are redirecting their nutrient flow into their roots. This method is more forgiving of inclement weather than the foliar application method, and provides a more target application of herbicide to the desired plant. 

Another method of chemical control for Tree-of-Heaven is known as the hack-and-squirt method. This method is conducted with the use of a hatchet or ax to make downward slicing cuts about 1-2 inches apart from one another into the sapwood around the tree trunk, placing these cuts as close to the ground as possible. Immediately after cutting, spray 50 percent triclopyr herbicide solution into the cuts so the bottom of the cuts are covered without excess liquid running out of the wounds. 

The last method of chemical control for Tree-of-Heaven is known as basal treatment. This method is one of the easiest to use, but only works on trees with a trunk that is 6 inches in diameter or less, and does risk overspraying or volatilization if not used cautiously. Basal treatment has also shown success when used in areas where no other technique is easily available. This treatment should be conducted in later winter, or early spring or summer, and is conducted by applying an oil-based triclopyr herbicide (such as Garlon 4) in a 20% solution, or by using another triclopyr product in a 25% triclopyr to 75% mineral or agricultural oil solution, and spraying it on the Tree-of-Heaven from basal height (about 4 to 4.5 feet from the base) to about 12 to 16 inches from the ground. 

All of these methods are effective control of Tree-of-Heaven, but even after treatment it is important to monitor and control in basal sprouts or root suckers that may appear to ensure that this invasive species is eradicated after treatment. 

If you have any other questions about identifying or controlling Tree-of-Heaven, please contact the Madison County Cooperative Extension Center at (828) 649-2411, or reach out to me directly at peyton_duckett@ncsu.edu.

Citations

Invasive Species Leaflet. (2010, March). NCDA&CS, Forest Service Division. https://www.ncagr.gov/divisions/nc-forest-service/is01/download?attachment. 

North Carolina State University. (n.d.). Ailanthus altissima. North Carolina Extension Gardener Plant Toolbox. https://plants.ces.ncsu.edu/plants/ailanthus-altissima/.

Oten, K. (2021, April 21). Spotted Lanternfly. NC State Extension Publications. https://content.ces.ncsu.edu/spotted-lanternfly.

Glen, C. (2024, April). Spotted Lanternfly Resources. NC State Extension, Gardening. https://gardening.ces.ncsu.edu/integrated-pest-management/insects-2/spotted-lanternfly-resource-page/.