What Is An Invasive Plant?

An invasive plant is a species that has become a weed pest that grows rapidly. It spreads and displaces other plants. Invasive plants typically appear on disturbed ground. The most invasive ones can actually invade existing ecosystems. Invasive plants can be very expensive to control and environmentally harmful.

A native plant is one that occurs naturally in a particular place without human intervention. Species native to North America are generally recognized as those occurring on the continent prior to European settlement.

Exotic plants are mostly European or Asian species that have been accidentally introduced or intentionally imported for their ornamental value or their ability to provide shade, windbreaks and/or erosion control.Translocators are native plants that have moved out of their original range into an area that favors their over-production.

Fast growth rate Grow well in a wide range of soil and growing conditions Some have high seed production with seeds that easily disperse and

sprout quickly Some have the ability to reproduce by roots or shoots, called suckering

Displace and reduce native plant species Destroy habitats that support native animals Change ecosystem processes so that they support aggressive and

exotic plants, animals and pathogens

What is an invasive plant?

What is a native plant?

Exotic or translocator?

What makes plants invasive?

Why are invasive plants bad?

Are difficult to control, can escape from cultivation and can dominate whole areas

Where did it come from?

Multiflora rose is an exotic species that is native to Japan and Korea and was introduced to the U.S. in the 1860s. It was originally planted as an ornamental shrub. In the 1930s conservation agencies began to promote it as a wildlife food and a cover plant for animal habitats. It was also used for erosion control and as living fences to confine livestock. Since its introduction, multiflora rose has spread rapidly from cultivation and readily invades open woodlands, forest edges, open fields, stream banks and other areas that have been subjected to land disturbance.How does it spread?

Multiflora rose is spread by seeds and by suckering. Suckering occurs both when the tips of arching stems root where they contact the ground and also when roots sprout new growth. Birds eat and disperse the seeds which is the primary means by which the shrub moves to new areas. Reproduction by suckering allows the plant to form dense, impassable thickets. An average plant may produce a million seeds per year. These seeds may still sprout for up to 20 years. Multiflora rose has a wide tolerance for soil, moisture and light conditions allowing it to spread to many habitats.How can it be controlled?

Regular mowing and repeated cutting in grassy areas inhibits seedling establishment. However, repeated cutting is often preferred to mowing because mowing will also damage native plants. Shrubs can be removed by digging and pulling. This is only effective when all of the roots are removed. Treatments with certain herbicides have also been effective at controlling the plant. Repeated treatments are needed because the seeds remain viable in the soil for many years. Also, two biological controls have been used successfully to manage the spread of multiflora rose. One is a native fungal pathogen (rose-rosette disease) this is spread by a tiny native mite. The second is a non-native seed-infesting wasp, the European rose chalcid.Native alternatives:

Common blackberryFlowering raspberryPasture roseSwamp roseWitch hazel

Multiflora Rose Rosa multiflora

Where did it come from?

Tree of heaven is an exotic species that is native to central China. It was introduced to the U.S. in 1784 by a Philadelphia, PA gardener. By 1840 it was commonly available from nurseries. Since its introduction, tree of heaven has sprouted up just about anywhere including alleys, sidewalks, parking lots, streets as well as in fields, roadsides, fencerows, woodland edges and forest openings.How does it spread?

Tree of heaven spreads by seeds and suckering. Suckering occurs when cut stumps and root fragments resprout. A single tree can produce up to 325,000 seeds per year. Once established, it grows dense stands that displace native plants. Tree of heaven also produces chemicals that kill or prevent other plants from growing near it. How can it be controlled?

Seedlings can be pulled or dug up. Care must be taken to remove the entire plant including all roots and fragments to prevent resprouting. Several herbicides have also proven to be effective in controlling tree of heaven. Targeting the removal of large female trees is the best way to control the spread. Female trees are responsible for the seed production. Before any control measures are used, it is important to correctly identify the plant because some native species are often confused with tree of heaven.Native alternatives:

Box elderSmooth sumacStaghorn sumacBlack walnutWhite ashTulip tree

Tree of HeavenAilanthus altissima

Princess TreePaulownia

Where did it come from?

Princess tree is an exotic species that is native to China. The Dutch East India Company introduced it to Europe in the 1830’s and North America in the 1840’s, both times as an ornamental. It is currently grown in plantations for wood to export to Japan and as a quick growing ornamental. It has escaped from both uses and grows in forests, fields, and along roadsides.

How does it spread?

Princess tree spreads by seed or suckering. One tree can produce 20 million seeds per year. Seeds are lightweight and winged so they are spread easily by wind and water. Suckering occurs from buds or roots after fires, cutting, or even bulldozing.

How can it be controlled?

Small seedlings can be hand pulled or dug out. Make sure to remove all of the root system to prevent sprouting. Large trees can be cut and then the sprouts will have to cut repeatedly. Large trees can be cut and the fresh stump can be painted with a herbicide to prevent sprouting. Small trees may be sprayed with a herbicide.

Native alternatives:

ServiceberryCatalpaRedbudFlowering dogwoodSassafrasSpicebushRed mulberry

Paper MulberryBroussonetia

Where did it come from?

Paper mulberry is an exotic species that is native to Japan and Taiwan. It was brought to the United States as an ornamental and escaped.

How does it spread?

Paper mulberry spreads by seed and suckering. Animals eat the berries and the seed passes through the digestive system unharmed. Generally the animals have moved far from the site where they ate the berries before the seeds are dropped. Suckering from root sprouts occurs abundantly after the tree is injured in some way.

How can it be controlled?

Seedlings can be pulled when the ground is moist if care is taken so that all of the roots are removed. Small trees can be cut to the ground followed by cutting of the root sprouts until they stop appearing. The trees can be cut and black plastic can be used to cover any new sprouts. The plastic creates unsuitable growing conditions, such as not enough sunshine, not enough moisture, and too much heat. Large trees can be cut and the fresh stump may be painted with a herbicide to suppress spouting.

Native alternatives:

Basswood SassafrasRed mapleHackberryBlack gum

Where did it come from?

Norway MapleAcer platanoides

Norway maple is an exotic species that is native to Eurasia from southern Scandinavia to Iran. It was introduced in Philadelphia in 1776 by John Bartram, a botanist. It was planted frequently in the 1950’s to replace American elms planted in neighborhoods that Dutch elm disease killed.

How does it spread?

It spreads mostly by wind. The seeds (samaras) are spread by the wind. Norway maple out competes native maples even in shady conditions.

How can it be controlled?

Seedlings can be hand pulled when the ground is wet or dug. Larger trees can be cut close to the ground.

Native alternatives

Red mapleAmerican beechSweet gumBlack gum

Where did it come from?

Black locust is a translocator that is native to eastern North America. Its native range is Pennsylvania to southern Indiana south to Georgia and

Black LocustRobinia

Louisiana and west to Iowa, Missouri, and Oklahoma. Outside of its range it is planted for mine reclamation projects, afforestation projects, and erosion control windbreaks.

How does it spread?

Suckering from roots and stumps occurs after the tree is cut. Seeds are spread by wind.

How can it be controlled?

Continuous cutting of trees, root sprouts, and tree sprouts will eventually kill the tree. It is also recommended to paint a freshly cut stump with a herbicide to reduce root and stump sprouts.

Native alternatives

Honey locustWhite ashSassafrasQuaking or bigtooth aspen