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 remove are burning bush, bush
honeysuckle, Callery pear, Chinese
yam, English ivy,
garlic mustard, 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 where it is naturally kept in check by predators, parasites, and competition, 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
• 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 feed on 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
• 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
• 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