Invasive Plants on Long Island: How to Identify Them and What to Plant Instead

Long Island's woods, meadows, and marshes are under pressure from a fairly short list of non-native plants that escaped from gardens and now spread on their own. Most of them are still for sale somewhere. Learning a dozen of them by sight, pulling them from your own yard, and planting the native that fills the same role is one of the most effective things a homeowner can do for pollinators and birds.

Our Invasive Species tool shows which of these have been documented near any zip code. This guide covers what they look like and what to plant instead.

Why invasive plants hurt pollinators

Insects are specialists. Most caterpillars can eat only the native plants they evolved with, and most native bees collect pollen from a narrow range of plants. When Japanese barberry replaces spicebush and blueberry in the understory, the spicebush swallowtails and blueberry bees simply disappear, and so do the songbirds that ate their caterpillars. Some invasives are worse than useless: black swallow-wort lures monarchs into laying eggs on it, and the caterpillars die.

New York regulates the worst offenders under 6 NYCRR Part 575. Prohibited species cannot be sold, bought, or planted. Regulated species can be sold with a warning but not released into the wild. Several others are not regulated but should be.

The usual suspects in Nassau and Suffolk

Vines

• Oriental bittersweet (Celastrus orbiculatus). Round leaves, orange capsules with red seeds strung along the stem in fall, vines thick enough to strangle trees. Prohibited. Plant instead: American bittersweet, trumpet honeysuckle.
• Porcelain berry (Ampelopsis glandulosa). Grape-like leaves and turquoise-to-purple speckled berries in September. Blankets the North Shore. Prohibited. Plant instead: Virginia creeper, fox grape.
• Japanese honeysuckle (Lonicera japonica). Fragrant paired white-and-yellow flowers, leaves that hang on into winter. Prohibited. Plant instead: trumpet honeysuckle, which hummingbirds prefer anyway.
• English ivy (Hedera helix). Evergreen, smothers the ground and climbs trees. Not regulated, but everywhere. Plant instead: foamflower, golden ragwort, Pennsylvania sedge.
• Mile-a-minute (Persicaria perfoliata). Perfect triangle leaves, barbed stems, blue berries. Spreading fast; report it. Prohibited.
• Black and pale swallow-wort (Vincetoxicum spp.). Twining vine with small dark purple or pink star flowers and milkweed-like pods. Deadly for monarch eggs. Prohibited. Plant instead: any native milkweed.

Shrubs

• Japanese barberry (Berberis thunbergii). Thorny, small spoon-shaped leaves, red berries all winter. Harbors far more ticks than native shrubs. Prohibited. Plant instead: winterberry holly, bayberry, highbush blueberry.
• Burning bush (Euonymus alatus). Corky winged twigs, scarlet fall color, seedlings carpeting nearby woods. Regulated. Plant instead: highbush blueberry or red chokeberry for the same fall color.
• Bush honeysuckles (Lonicera maackii and relatives). Opposite leaves, hollow twigs, red berries. Prohibited. Plant instead: spicebush, arrowwood viburnum.
• Multiflora rose (Rosa multiflora). Arching thorny canes, clusters of small white flowers, fringed stipules. Prohibited. Plant instead: Virginia rose, pasture rose.
• Autumn olive (Elaeagnus umbellata). Silvery leaf undersides, silver-flecked red berries. Prohibited. Plant instead: bayberry, serviceberry.
• Butterfly bush (Buddleja davidii). Not regulated, but it feeds only adult butterflies, hosts no caterpillars, and seeds into waste ground. Plant instead: sweet pepperbush, buttonbush, Joe Pye weed.

Trees

• Tree-of-heaven (Ailanthus altissima). Huge compound leaves, rancid-peanut smell, suckers everywhere, and the favorite host of spotted lanternfly. Prohibited. Do not just cut it; it resprouts by the dozen. Plant instead: black cherry, staghorn sumac.
• Norway maple (Acer platanoides). Milky sap from a snapped leaf stem, dense shade, seedlings everywhere. Regulated. Plant instead: red maple, white oak.
• Callery pear (Pyrus calleryana). White April flowers that smell like fish, thorny wild offspring. Not yet regulated in New York, banned next door. Plant instead: serviceberry, redbud, flowering dogwood.

Herbaceous plants and grasses

• Garlic mustard (Alliaria petiolata). Garlic-scented kidney-shaped leaves in year one, white four-petaled flowers in April of year two. Poisons soil fungi. Prohibited. Pull before it seeds. Plant instead: wild ginger, foamflower.
• Japanese stiltgrass (Microstegium vimineum). Delicate sprawling grass with a silver stripe down each leaf. Prohibited. Pull or trim in late August. Plant instead: Pennsylvania sedge, white wood aster.
• Mugwort (Artemisia vulgaris). Gray-green, sage-scented, silvery leaf undersides, the weed of every Long Island roadside. Not regulated. Plant instead: wild bergamot, mountain mint, little bluestem.
• Purple loosestrife (Lythrum salicaria). Magenta spikes in wet ground in July. Prohibited. Plant instead: blue vervain, New York ironweed, swamp milkweed.
• Phragmites (non-native Phragmites australis). The 15-foot reed walling off every marsh. Prohibited.
• Lesser celandine (Ficaria verna). Glossy heart leaves and yellow buttercups in March; gone by June. Prohibited. Plant instead: golden ragwort.
• Chinese silver grass (Miscanthus sinensis). Tall ornamental grass with a white leaf midrib, seeding into meadows. Regulated. Plant instead: switchgrass, little bluestem, Indiangrass.

How to remove them

1. Identify first. Photograph the plant and confirm it with iNaturalist or the New York Flora Atlas before you pull. Several natives resemble invasives (staghorn sumac vs. tree-of-heaven, American vs. Oriental bittersweet).
2. Time it. Pull annuals and biennials (garlic mustard, stiltgrass, mile-a-minute) before they set seed. Cut woody plants in late summer when root reserves are lowest.
3. Get the root, or treat the cut stump. Most woody invasives resprout from any root left behind. A weed wrench works wonders on barberry and honeysuckle.
4. Bag seeds and fruit. Do not compost them.
5. Replant immediately. Bare ground grows the next invasive. Put a native in the hole the same day.
6. Report it. New York's iMapInvasives lets land managers track spread, and early reports of mile-a-minute, kudzu, and lesser celandine really do get a response.

For official lists, see the New York DEC prohibited and regulated species list and the Suffolk County Do Not Sell list on our Resources page. Cornell's Alternatives to Ornamental Invasive Plants is the best single guide to swaps.

Sources

• New York State Department of Environmental Conservation, Prohibited and Regulated Invasive Plants (6 NYCRR Part 575) - https://www.dec.ny.gov/docs/lands_forests_pdf/isprohibitedplants2.pdf
• Suffolk County, Do Not Sell/Transfer List - https://pb.state.ny.us/assets/1/6/SC_Do_not_sell_list.pdf
• Cornell New York State Integrated Pest Management, Invasive Ornamental Plant Alternatives - https://cals.cornell.edu/new-york-state-integrated-pest-management/eco-resilience/invasive-species/invasive-ornamental-plant-alternatives
• New York Natural Heritage Program, NY iMapInvasives - https://www.nyimapinvasives.org/