Invasive Plants

Listed below are just a few of the most common invasive plants in Cambria County. For a comprehensive list of invasive plants in Pennsylvania, click the button above.

 
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Japanese Knotweed (Fallopia japonica)

Japanese knotweed was introduced to the US in the late 1800s as an ornamental and to stabilize stream banks. You’ve probably seen it covering banks along streams and rivers in the county or along the sides of roads. Here’s some tips to help you identify it:

  • Large (up to 12”), bright green, heart-shaped leaves

  • Green and red, hollow stems that resemble bamboo

  • Grows up to 11 feet tall

  • Flowers appear in late summer, white clusters 3-4” long

  • Commonly found along wetlands, stream banks, and river banks

The problem with knotweed is that it spreads very rapidly using its root system, and fragments and seeds can flow downstream and spread. It grows so tall and thick that it smothers out all native vegetation, preventing anything else from growing. Although it was planted for stream bank stabilization, it provides very poor erosion control compared to native plants.

 
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Tree-of-heaven (Ailanthus altissima)

Tree-of-heaven was introduced to Pennsylvania in the 1700s as a unique and fast-growing ornamental tree. By the 1900s, the tree lost its popularity because of its root sprouts and smelly odor. Now, you’ve probably seen it along highways, on the edges of fields, and in the forest. Here’s some tips to help you identify it:

  • One leaf can be 1-4 feet long with 10-40 leaflets

  • Leaflets are lance-shaped with smooth edges and two teeth at the base

  • When crushed, leaves smell like burnt peanut butter

  • Leaves turn yellow in falls, our native sumac turns red

  • Smooth, brownish green bark that resembles the skin of a cantaloupe

The problem with tree-of-heaven is that each tree can produce more than 300,000 seeds each year, and seeds are wind dispersed so they can travel long distances. The roots of the tree also produce a chemical that can prevent other plants from growing in the soil around them. Tree-of-heaven is also the favorite tree of the spotted lanternfly (an invasive insect), so reducing populations of the tree can also slow the spread of spotted lanternfly.

 
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Oriental Bittersweet (Celastrus orbiculatus)

Oriental bittersweet was introduced to the United States in the 1860s from east Asia and has become an extremely aggressive and damaging invader of natural areas. It chokes out native plants by smothering them with its dense foliage and strangling stems and trunks. Here’s some tips to help you identify it:

  • Long vines up to 60 feet in length

  • Round leaves 3 to 4 inches long with toothed edges

  • Leaves turn bright yellow in summer

  • Yellow-green flowers in late spring

  • Red fruit through winter

  • Stem bright green

It reproduces by seed and vegetatively by sprouting from an extensive root system. Its conspicuous fruit is spread primarily by birds and persists from late summer through winter.