What Makes A Plant Invasive?

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Not all non-natives become a problem. Those that do share many characteristics. They:

  • Produce abundant viable seeds. For example, each garlic mustard plant can produce hundreds to thousands of seeds.

  • Produce seeds that germinate and leaves that leaf out early in the spring, and they keep their leaves late into the fall, allowing them to photosynthesize earlier and later than native plants. For example, Norway maple seedlings can be 6 inches tall before native maples sprout, and buckthorns keep their leaves into November, long after native plants have lost theirs.

  • Have few pests or diseases. Non-native plants did not arrive in Vermont with the accompanying pests and diseases that kept them in check in their native environments.

  • May produce chemicals that make it difficult for other plants to grow nearby.

  • Invade a wide variety of soil types, moisture regimes and light conditions. Invasives are typically generalists and can be difficult to kill.

  • Often produce monocultures over large areas so few other species can reproduce and grow. For example, wild chervil, Japanese knotweed and goutweed are just a few invasives that spread quickly and cover large areas, eliminating the diversity of species that once grew on that site.

  • Reproduce both sexually and asexually (through a rhizomatous root system), making it easier for them to spread far and wide.

Where do invasives come from?

Human-caused alterations to the Vermont landscape over the past few hundred years have increased opportunities for invasive plants to further establish. Invasive terrestrial plants arrive through many vectors, or pathways, including ship ballast, “wildlife” plantings, roadways and the horticultural industry.  They often get a foothold in areas with soils that have been disturbed in the following ways: road building,.grading and maintenance, residential development, forestry activities, grazing, ditching, mowing and erosion control, Recreationalists can escalate the spread of invasives by inadvertently carrying seeds on their clothing, bike wheels and other recreational equipment. Natural disturbances, such as floods and landslides, provide other avenues for invasive species to establish.

Frequently Asked Questions