Long Island’s Silent Invaders: How These Foreign Trees Are Quietly Taking Over Your Backyard

Long Island homeowners are facing an unprecedented ecological crisis that many don’t even realize is happening in their own backyards. Long Island is being overrun with invasive plants. Drive along any highway, and the woods along the way are covered with a mass of vines that smother and kill off our native trees. At present, invasive plants cost us an estimated $120 billion a year.

The Most Common Invasive Tree Species on Long Island

Long Island’s invasive trees and shrubs include the ubiquitous tree-of-heaven, Japanese angelica, Norway maple, and sycamore maple, plus some newcomers such as glossy buckthorn and Callery pear, as well as thorny multiflora rose and autumn olive shrubs. Many of the trees we see growing on Long Island are highly invasive and non-native — commonly Chinese exotics brought here over 200 years ago. Today most Long Island soils harbor viable seeds dispersed from their descendants via wind, birds, or mammals years to decades ago. Under the right circumstances — often sun exposure when land is cleared — these seeds will germinate and grow to out-compete native species.

Tree-of-Heaven: The Most Aggressive Invader

Tree-of-heaven is a large deciduous tree, generally 40 – 60′ tall at maturity. Its leaves alternate along the stems, and are pinnately compound, composed of 11 to 41 leaflets per leaf. Leaflets are 3 – 5″ long and often have 2 to 4 blunt teeth at the base but are otherwise smooth along the edges. The key identification feature is an unpleasant odor that occurs when the leaf stems are crushed. One factor contributing tree-of-heaven’s ability to dominate in disturbed habitats is its extremely high rate of seed production. One individual female can produce 10 million seeds over 40 years of reproduction.

Norway Maple: The Deceptive Look-Alike

The Norway Maple (Acer platanoides) is a classic example of an invasive tree—with ties to the early American nursery trade, it was planted extensively in North America for its aesthetic appeal and horticultural value before eventually spreading into natural areas where it disrupts native plant communities. The Norway Maple is a medium to large deciduous tree with a mature height ranging from 40 to 90 feet depending on growing conditions. Its waxy dark green leaves are opposite and palmately lobed. The easiest way to identify this tree is to break the leaf at the node where it joins the stem (petiole). You’ll notice white sap at the break, whereas saps from other maples are clear.

Why These Trees Are Dangerous to Your Property

Invasive species like the Norway maple and Black locust outcompete native trees such as the Oak and Hemlock. They spread rapidly, consuming sunlight, water, and nutrients, which leaves native species struggling to survive. It spreads by seeds into nearby disturbed forest communities, where its dense canopy reduces light levels and limits the growth of wildflowers and tree seedlings. The dense canopy of Norway maple limits the growth of sugar maple and other native tree seedlings, reducing forest diversity. Wildflower diversity is reduced beneath Norway maple because the dense canopy reduces light levels.

With no natural enemies, that is insects that have evolved to feed off them, they grow unchecked. They outcompete our native plants for nutrients, light and water. This creates a domino effect that impacts local wildlife, reduces property values, and can even create safety hazards from weakened native trees.

Professional Management Strategies for 2024

Effective invasive tree management requires a multi-faceted approach that combines proper identification, timing, and professional techniques. We help put together invasive species management plans that use proactive integrated vegetation management programs, preventative treatments, and monitoring to help meet our clients goals. Our experts can help you find the right solution for the most cost-effective treatment through a diverse range of services, such as surveys and assessments, control plans, herbicide applications, mechanical harvesting, and monitoring and maintenance.

Mechanical Control Methods

Three broad categories cover most invasive plant control: mechanical, chemical, and biological. Mechanical control means physically removing plants from the environment through cutting or pulling. Tree and Shrub Removal addresses removing saplings — defined as young trees four inches or less in diameter at breast height. Larger tree removal may require a town permit and some trees may need to be debarked before cutting to prevent root suckers.

However, mechanical methods alone are often insufficient. Control of tree-of-heaven is particularly challenging due to its tendency to send up root suckers if the main stem is damaged. Ineffective control can actually make an infestation worse. Mechanical methods, such as cutting or mowing, are ineffective, as the tree responds by producing large numbers of stump sprouts and root suckers. When cutting tree-of-heaven is necessary to remove potentially hazardous trees, it is best to treat with an herbicide first, wait for symptoms to develop (approximately 30 days), and then cut.

Chemical Treatment Strategies

To control tree-of-heaven you must control the root system. The most effective way to do this is by applying a systemic herbicide at the optimum time of year. The most effective way to do this is by applying a systemic herbicide at the optimum time of year. This is best accomplished in mid to late summer, July through September. One of the simplest methods for removing mature trees, outlined here by Penn State Extension, is the hack-and-squirt method. The idea is to use a hatchet to make evenly-spaced incisions around the circumference of the stem and apply an herbicide in the incisions. The herbicide will make contact with the vascular tissue and be carried into the roots.

Prevention and Follow-Up Care

Soon after removing tree seedlings, cover the open ground with mulch (a thick layer of leaves) or replace them with native, shade loving plants (plugs or seeds) such as white wood aster Eurybia divericata, and then mulch. This hardy, fast growing native species is a beautiful shade loving weed suppressant. It self-seeds, blooms throughout September and is a source of nectar and pollen for native pollinators.

Why Professional Tree Services Are Essential

Given the complexity and potential dangers of invasive tree management, professional intervention is often necessary. If you do not want to remove these woody plants yourself, you can hire contractors to treat and remove invasive plants. Find out more about how to hire a tree care professional. Professional arborists have the expertise to properly identify invasive species, understand the optimal timing for treatments, and safely handle the chemicals and equipment required for effective control.

For Long Island residents dealing with invasive tree species, working with experienced professionals like Tree Services Long Island ensures that removal and management strategies are implemented safely and effectively. Miguel’s Tree Service is a locally-owned and operated tree company dedicated to delivering exceptional tree care services in Suffolk County, NY. With 15 years of experience in the industry, we have earned a reputation for our expertise, professionalism, and commitment to customer satisfaction. Our tree company consists of skilled arborists and tree care specialists passionate about maintaining your trees’ health and beauty.

The Importance of Acting Now

This disaster was centuries in the making, but has been accelerating as they take hold and spread unchecked, their progress unnoticed. The task before us all is immense though. The sheer amount of invasive plants, combined with our general ignorance of the problem, is more than daunting. However, early intervention is key to preventing these invasive species from overwhelming your property and the broader Long Island ecosystem.

You plant natives where ever you can while removing the invasive ones, starting in your yard and your community. You put back what belongs and remove what doesn’t. Your efforts to control invasive species can help protect Long Island’s native tree population. Removing invasive trees and planting native ones are key actions you can take. The more you engage in these activities, the better the health of Long Island’s forests will be.

The fight against invasive tree species on Long Island requires immediate action, proper identification, and professional management strategies. By understanding these threats and working with qualified tree service professionals, homeowners can protect their properties while contributing to the restoration of Long Island’s native ecosystems. The time to act is now – before these silent invaders completely transform our landscape forever.