Growing your results…
Here's a number that puts the native vs. invasive question in stark terms: a native oak tree supports over 550 species of moth and butterfly caterpillars. A non-native gingko tree — widely planted, widely praised for its fall color and disease resistance — supports 5.
That's not a minor difference in ecological value. That's a functional collapse of the food web at the tree level. And it plays out across thousands of species of non-native ornamental plants sold at garden centers every year.
Understanding why that gap exists — and which plants are causing the most damage in your landscape — is the first step toward making genuinely impactful planting decisions.
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The relationship between plants and insects is not random. It's the result of millions of years of co-evolution. Native caterpillars, in particular, have evolved the ability to break down specific defensive chemicals (phytotoxins) produced by the native plants in their region. A monarch caterpillar can sequester the cardiac glycosides in milkweed because it evolved to do exactly that. Put it on a plant it hasn't co-evolved with, and it starves.
This specificity is pervasive. Research by Dr. Doug Tallamy at the University of Delaware found that the majority of Lepidoptera caterpillars are constrained to feed on just a few plant genera. When a landscape replaces native plant communities with ornamental non-natives — even beautiful, non-invasive ones — it removes the food that specialist insects need to complete their life cycle.
The difference between a native and a non-native plant isn't visible on the outside. It's in the biochemistry.
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Native plants — species that evolved in a specific region and have formed symbiotic relationships with local wildlife over thousands of years. These are the plants that support the insects that feed the birds that sustain the ecosystem.
Non-native (exotic) plants — species introduced from other regions or countries, intentionally or accidentally. Not all non-natives are harmful; some garden plants like tulips and hyacinths are non-native but not invasive. However, most non-natives provide substantially less wildlife value than natives, even when they're not actively spreading.
Invasive plants — non-native species that cause ecological or economic harm by spreading aggressively and displacing native vegetation. These are the highest-priority targets for removal. The National Invasive Species Information Center defines invasive plants as those "likely to cause economic or environmental harm or harm to human health."
One important nuance: invasive ≠ non-native. Some native plants can behave invasively in disturbed conditions. Sumac, for example, can spread aggressively into prairie habitats. The harm caused by true invasive non-natives, however, is typically far more severe because they lack the ecological checks — predators, pathogens, competitors — that evolved alongside them in their native range.
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One of the most widely planted ornamental shrubs in North America — and one of the most ecologically damaging. Japanese barberry alters soil chemistry by raising soil pH and nitrogen levels, creating conditions that favor its own spread and suppress native understory plants. Dense barberry thickets also create ideal microhabitats for blacklegged ticks (Ixodes scapularis), increasing Lyme disease risk in infested areas.
Several states, including Pennsylvania, New York, and Massachusetts, have banned or restricted its sale.
Replace with: Native spicebush (Lindera benzoin), which is a larval host for spicebush swallowtail butterflies and provides berries for migrating thrushes; or native viburnums (Viburnum spp.).
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Another ubiquitous landscape shrub prized for brilliant fall color. In natural areas, birds consume the berries and spread seeds into forests, where burning bush outcompetes native shrubs in forest edges and understory. It supports virtually no native wildlife.
Also banned or restricted in several New England states.
Replace with: Native highbush blueberry (Vaccinium corymbosum) for wet sites, or native chokeberry (Aronia spp.) for fall color with real wildlife value — chokeberry berries are consumed by more than 30 species of birds.
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Sold as an easy-care groundcover, English ivy is an ecological dead zone. It forms dense mats that prevent native seedlings — including tree seedlings — from establishing, and can climb and "ivy strangle" mature trees by adding weight and preventing light from reaching leaves. It supports almost no native insects.
Replace with: Native groundcovers like wild ginger (Asarum canadense), native sedges (Carex spp.), or wild strawberry (Fragaria virginiana), which is a keystone plant in many ecoregions.
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A wetland invasive that forms dense monocultures, displacing the native cattails, sedges, and bulrushes that support wetland wildlife. While purple loosestrife provides some nectar to generalist bees, it supports virtually no specialist insects and eliminates the habitat structure that marsh birds and amphibians require.
Once established, it's difficult to eradicate. Early identification and removal is essential.
Replace with: Native swamp milkweed (Asclepias incarnata), blue flag iris (Iris versicolor), or native Joe-Pye weed (Eutrochium spp.) for wet areas.
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The native trumpet honeysuckle (Lonicera sempervirens) is an excellent hummingbird plant. Its non-native relatives are ecological liabilities. Tatarian honeysuckle's berries are low in fat and nutritional value — and research has found that birds consuming them during fall migration may actually gain less weight than birds eating high-quality native berries, impairing long-distance migration.
Replace with: Native trumpet honeysuckle (L. sempervirens) for the vine form; native viburnums or serviceberries for shrub form.
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This is a nuanced one: there is a native North American Phragmites (P. australis subsp. americanus), and an introduced European strain that is invasive. They look nearly identical, but the European strain spreads far more aggressively and forms monocultures in wetlands that displace native marsh vegetation. DNA testing or consultation with a wetland ecologist is sometimes needed to distinguish them.
Replace with: Native cattail (Typha latifolia), bulrush (Schoenoplectus spp.), or native sedges for wetland restoration.
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A common pushback: "My butterfly bush (Buddleia davidii) is covered in butterflies — how can it be bad for wildlife?"
Butterfly bush does provide nectar for adult butterflies. But it is not a larval host plant for any North American butterfly or moth species. Adult butterflies need nectar; they need host plants to reproduce. A landscape full of butterfly bush nectar but no host plants is the ecological equivalent of a fast food strip without anywhere to live or raise children.
Additionally, butterfly bush is invasive in parts of the Pacific Northwest, Oregon, and Washington, where it spreads along river banks and disturbs native riparian vegetation.
The standard recommendation: if you want to support butterflies, plant their larval host plants first. Then add nectar sources. Native alternatives — like native Joe-Pye weed, coneflowers, and goldenrod — provide both nectar and host plant function simultaneously.
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Walk your property and ask these questions about each plant:
You don't need to rip out everything at once. Prioritizing invasive removal first, then gradually replacing low-value ornamentals with keystone natives over time, produces significant ecological gains even in small suburban landscapes.