Why Invasive Plants are Bad for New Jersey Landscapes

An invasive species is not a species that is inherently evil or bad; it is a species that—due to human activity—spreads rapidly and often in large numbers into natural (and often cultivated) areas, causing environmental harm to ecosystems. Because invasive species are the products of distant ecosystems, they have few or no checks on their spread. Being non-native, they also do not serve as food for pollinators and wildlife. In gardens and parks, the damage often begins quietly: one ornamental plant escapes cultivation, spreads by seed or runners, and slowly replaces the diverse native plant community that birds, butterflies, moths, bees, and other wildlife need.

Why Species Become Invasive

Humans make species invasive by moving them across barriers they could not cross on their own. We import plants for gardens, roadsides, erosion control, screening, and agriculture; we also move seeds and plant fragments accidentally in soil, machinery, nursery stock, cargo, and yard waste. Once a species lands in a place where it can thrive without the insects, diseases, predators, or competitors that kept it in check, it can spread rapidly into disturbed landscapes and displace native species.

The Ecosystem will NOT Adapt Quickly enough

Evolution does not happen on a gardener’s schedule. The relationships among native plants, insects, birds, fungi, and soils developed over thousands to millions of years. A plant can be moved across the world in a week and planted by the thousands in a decade, but the ecological relationships that make it useful, limited, and balanced do not arrive with it.

Native insects cannot simply switch to every new plant that appears. Many are tied to particular plant families, genera, or species because those relationships evolved over deep time. Birds may eat the berries of an invasive shrub, but that does not mean the plant supports the caterpillars, seeds, nesting habitat, and seasonal food webs that native plants provide. A forest understory can be transformed in a few decades, while the relationships needed to make that new plant community ecologically functional may take thousands of years to develop, if they develop at all.

“Nature always finds a way” is from Jurassic Park, a science fiction movie. It is not a management plan. Adaptation is real, but it is slow, uneven, and costly. In the meantime, invasive plants can form monocultures, suppress native seedlings, alter soils, change fire behavior, and make removal more difficult with every passing year. Waiting for the ecosystem to adjust means accepting decades of lost biodiversity, weakened food webs, and fewer opportunities for native plants and wildlife to recover.

A changed world does not require resignation. It requires better choices. We may not be able to return every landscape to an earlier condition, but we can stop adding known invasive plants, remove the worst offenders where possible, and replant with species that still participate in New Jersey’s living ecological relationships.

We Just Don’t Know Enough to Plant Non-Natives Safely

Many non-native plants seem harmless when they first appear in gardens. Some stay that way, for now. But the problem is that we usually do not know which plants will remain well-behaved over time, across different soils, climates, neighborhoods, and natural areas. A plant can be sold for decades before people notice that it is spreading from yards into parks, roadsides, wetlands, or forests.

This uncertainty is called a lag phase: the gap between when a plant is introduced and when people finally recognize that it is spreading. During that gap, the plant may be building up in gardens, roadsides, seed banks, or nursery inventories without looking like a crisis. Then a change in planting density, climate, disturbance, pollinators, seed dispersers, or genetics can make it take off. Callery pear is the classic example: Bradford pear was once treated as effectively sterile, but when other Callery pear cultivars were planted nearby, they cross-pollinated and produced viable seed, creating the thorny wild pears now spreading through fields and forest edges. Purple loosestrife followed a similar warning pattern: garden cultivars once promoted as sterile were later shown to cross with wild plants and produce viable seed. The larger lesson is that a plant can look safe for years, even decades, before the conditions line up for invasion.

Invasiveness is often discovered after the damage has already begun. A plant may look contained in one garden but behave differently when birds spread its seeds, when a warmer winter lets more seedlings survive, or when it reaches a disturbed forest edge where competition is low. By the time a species is recognized as invasive, it may already be widespread and expensive to remove.

Cultivars and “sterile” selections are not a complete answer. Some do not stay sterile under real-world conditions. Some produce viable seed when planted near related varieties. Others may still spread by roots, runners, fragments, or dumping. Even when a particular selection is less fertile, it can keep demand alive for a species that should be leaving the nursery trade.

The burden of proof should not fall on the forest, the roadside, or the volunteer removing seedlings ten years later. If a plant is non-native, closely related to known invasives, produces abundant seed, spreads vegetatively, or is already causing trouble in nearby states, gardeners should be cautious. “Not yet known to be invasive” is not the same as safe.

New Jersey’s Invasive Species Management Act was signed in January 2026. For gardeners, the practical point is simple: the law begins moving known invasive plants out of sale, distribution, import, export, and propagation unless a conditional-use waiver applies.

The law phases in restrictions over time. Legislative statements describe a 13-month phase-in for propagation and importation and a 49-month phase-in for sale, distribution, and export. For compliance questions, use the official state guidance rather than this page.

Which plants are invasive?

There is more than one useful list. For a home gardener, the best question is not only “is it legally regulated?” but also “is it a known landscape escapee in New Jersey or the Mid-Atlantic, and is there a better native plant for the same garden job?”

• Banned-from-sale plants: The profiles below include all 30 plants on New Jersey’s current banned-from-sale invasive plant list. Read NPSNJ’s law update
• Strike Team status: NJISST tracks widespread, target, and watch species and provides control guidance. Open Strike Team Info Center
• Rutgers alternatives: Rutgers FS1353 organizes invasive ornamentals by plant type and suggests native replacements. Open Rutgers FS1353
• NPSNJ resources: NPSNJ has background pages and a talk specifically about natives replacing invasives. Open NPSNJ talk page

Invasive plant profiles and native alternatives

The guide below includes all 30 plants currently listed by NJDA as regulated invasive plant species, plus several additional common landscape offenders. This is not a one-for-one shopping list. Start by identifying the invasive plant, then choose native replacements that match the actual site: sun, shade, soil moisture, available space, salt exposure, and maintenance goals.

Deer will ultimately eat anything if hungry enough, and, without natural predators, there is massive overpopulation. Buying only deer-resistant plants reduces biodiversity. Instead of trying to avoid deer pressure, protect your plants from deer pressure.

How to start removing and replacing invasives

1. Inventory: Identify what you have before cutting. Confirm scientific names when possible.
2. Prioritize: Start with plants producing seed, spreading into natural areas, or listed as regulated or high-priority.
3. Remove carefully: Use the least disruptive method that works. For large woody plants, consult technical guidance or a professional.
4. Replant promptly: Do not leave bare soil. Replace with natives matched to light, moisture, soil, deer pressure, and mature size.

For detailed control methods, use the New Jersey Invasive Species Strike Team guidance. This page focuses on garden replacement choices, not herbicide instructions or site-specific restoration plans.

Print companion: the NPSNJ trifold

The brochure is useful for tabling, garden-center conversations, and quick reference. Request some from your local chapter or info@npsnj.org

Download the full trifold PDF