Horticulture & Landscaping: the largest human-driven pathway for invasive species spread

The horticulture industry, from ornamental plant sales to the movement of nursery soil, mulch, and seed mixes, remains one of the primary sources of invasive plant introductions in North America (USFS 2024). Many invasive plants thrive because they produce large quantities of seed, spread via aggressive root systems, and are easily dispersed by birds, wind, and human activity (USDA 2023).

"Over 60% of invasive plants in the U.S. originated in horticulture."

— U.S. Forest Service, 2024

How this pathway works

Invasive species move through horticulture in several predictable, well-documented ways:

• Many invasive plants were originally introduced as ornamentals and later escaped cultivation, driven by prolific seed production and tolerance for disturbed soils (USFS 2024).
• Seeds and root fragments hitchhike in nursery pots, bagged soil, compost, and fill dirt, enabling long-distance spread (USDA 2023).
• Some invasives regenerate from small root fragments, spreading aggressively whenever soil is moved (USFS 2024).
• Many invasive shrubs and vines rely on birds and wind to move seeds across large areas, accelerating escape from planted landscapes (USFS 2024).
• Mud and seeds on shoes, tools, mowers, and trailers can introduce invasive plants into forests, parks, and natural areas (USFS 2024).

Why this vector matters

Because horticulture is intentional, widespread, and economically embedded, it creates persistent, long-distance invasion pathways that outpace management efforts. Invasive plants degrade wildlife habitat, reduce biodiversity, and contribute to the decline of threatened species across the U.S. (USFS 2024).

High-risk plant categories

Several plant groups consistently drive new invasions through the horticultural pathway:

What reduces risk

Effective prevention comes from simple, high-impact choices that anyone buying plants or soil can make:

• Choose regionally native plants that support local ecosystems.
• Buy from native-focused nurseries that propagate local ecotypes.
• Inspect soil and mulch before planting — ask your supplier where it originates.
• Avoid generic wildflower mixes that often contain invasive species.
• Clean tools and equipment between sites to prevent seed transfer (USFS 2024).
• Remove invasive ornamentals already in your garden and replace them with native alternatives.

Texas spotlight: plants to avoid

For readers in Texas, several widely sold ornamentals are now major ecological threats to forests, riparian corridors, and grasslands:

• Chinese privet — dense thicket-forming shrub that outcompetes native understory plants
• Nandina domestica — berries toxic to birds; spreads into wooded areas from garden plantings
• Japanese honeysuckle — documented as an invasive forest plant by the U.S. Forest Service (USFS 2024)
• Bermudagrass — aggressive turf grass that invades native grasslands and riparian zones
• Bradford pear — escaped from suburban plantings and now spreading rapidly across the South

These species spread aggressively into forests, riparian corridors, and grasslands, displacing native plants and reducing habitat quality for wildlife (USFS 2024).