One of the major tasks of the Floracliff staff is eradicating invasive exotic plants from the preserve that are out-competing native species. Some of the most invasive plants we work with are burning bush, bush honeysuckle, Chinese yam, English ivy, garlic mustard, Japanese honeysuckle, Japanese stilt grass, multiflora rose, privet and wintercreeper. Many of these plants are popular ornamental plants that have been dispersed by wildlife eating the seeds and depositing them elsewhere.

An invasive exotic plant is “an alien species whose introduction does or is likely to cause economic or environmental harm, or harm to human health” (Official U.S. definition). The following are characteristics typically found in invasive plants:

• Fast growth - An exotic plant may not spread as widely in its native environment but when introduced to a more favorable environment it can take over, excluding native vegetation. Some of these species also have the ability to grow over other forms of vegetation and are not impeded by other plants. This is exhibited by the notorious kudzu vine, which can grow up to a foot per day.
• Early maturation - Plants that reach a seed-bearing stage early in their life spans have the ability to spread faster. This leads to a plant becoming invasive because it can reseed areas faster than the surrounding native plants. Early maturation means that there is less time for the plant to become susceptible to disease, predators, and removal before it can reproduce. Autumn olive, an invasive shrub found in Kentucky, can produce seeds after three years.
• Large numbers of fruits and seeds - Some exotics have the ability to produce large numbers of seeds, hence they have large numbers of offspring to spread to surrounding areas, allowing them to create a monoculture. Garlic mustard can produce hundreds to thousands of seeds per plant.
• Effective seed dispersal - Seeds of invasive plants can spread through various mechanisms. Plants dispersed by animals such as bush honeysuckle and burning bush have developed brightly colored seeds that attract birds and other wildlife, which then deposit the seeds in a new location. Other plants, such as tree-of-heaven spread their seeds through the wind. Some invasive species have a tendency to grow near water bodies, such as garlic mustard and Japanese knotweed, which means their seeds spread through water currents and are distributed downstream colonizing entirely new areas.
• Longer growing period - Bush honeysuckle leafs out as early as February and keeps its leaves into November, giving it a longer growing period than most native plants. This characteristic allows plants to photosynthesize longer into the seasons, allowing them to add mass and grow when other plants are not. It also allows plants to obtain nutrients and water from the soil when other plants are not as active.
• Ability to create dense shade/thickets - Many of the characteristics of invasive plants allow them to quickly colonize an area, creating a monoculture in a relatively short time frame. This rapid growth blocks necessary light to species that live underneath the dense thicket of an invasive species. Dense thickets crowd areas taking space, nutrients, and water from native species. These thickets build dense root structures preventing native plants from establishing their own root structures. Winter creeper, a vine, can create a carpet-like mass along the forest floor.
• Allelopathy - The ability of one plant species to produce and release chemicals that are toxic to other plant species is known as allelopathy. When a plant is allelopathic, often times no growth will be observed within a certain radius around the plant. Garlic mustard and tree-of-heaven are two invasive plants that have exhibited allelopathy.
• Free of pests - Introduced species are not always recognized by native species as food or as habitat. Since these species are not from the native environment, native herbivores are not accustomed to the taste of introduced species and will the surrounding native vegetation, further promoting the growth and spread of the invasive species by eliminating competitors. For example, deer do not like the taste of garlic mustard but enjoy native tree sprouts and herbaceous plants.

Why should we be concerned that these plants are taking over our natural areas? Because they are greatly decreasing biodiversity and are considered the number two threat to native ecosystems, second to habitat destruction. Biodiversity is defined as “the variety of life and its processes; and it includes the variety of living organisms, the genetic differences among them, and the communities and ecosystems in which they occur”. Biodiversity benefits mankind through:

• Agriculture - The majority of the world’s population is fed on less than 20 domesticated plants. The wild plant gene pool, including relatives of these crops, is important in potentially providing disease resistance, improved productivity, and tolerance of various environmental conditions. Strawberries, grapes, blueberries, cranberries, plums, beans, squash, wild rice, walnuts, pecans, and sunflowers are just some of the crops that have wild relatives native to North America. We also rely on a variety of native insects to pollinate our crops and control pests.
• Medicine - Over 40% of prescribed medicines in the United States contain chemicals originally from plants. Salicylic acid from willow trees was used to make aspirin and taxol, from the Pacific yew, has been used to fight cancerous tumors. Only 2% of the world’s estimated 250,000 plants have been thoroughly studied for their potential medical uses.
• Products - North American plants have been used in the production of many products we use on a daily basis such as housing, furniture, sports equipment, paper products, insect repellants, lubricants, sunscreens, and more.
• Resource protection - Native vegetation helps stabilize soil and water resources. Forests help purify water and keep the streams cool for aquatic life. They also act as a buffer against floods and droughts. Native plants are important in the formation of soil, as leaves fall and plants die. In areas where bush honeysuckle is invading forests, the leaf litter is greatly reduced.
• Intrinsic values - Local natural areas provide us with places for personal inspiration, relaxation, and enjoyment. The native plants and animals found in these places add to their uniqueness and to the recognition of a place we also call home.

• Avoid planting invasive plants
• Landscape with native plants
• Avoid using “wildflower” seed mixes
• Early detection and removal
• Minimize disturbance in natural areas
• Educate yourself and others
• Ask nurseries not to carry invasive plants
• Volunteer!