Paulownia is becoming a royal pain!

Posted on February 23, 2012

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Posted by guest blogger:   Eric Boyda,  Iron Furnace Cooperative Weed Mangement Area

Showy springtime flowers seduce gardeners into planting invasive tree

Spring is near, and many plants are beginning to flower. As the exciting outdoor display of flowers progresses, it is important to recognize that not all flowering plants are as docile and charming as they appear to be.

Native to western China, paulownia or empress tree (Paulownia tomentosa) was first introduced to the US in the early 1800’s as an ornamental for its showy sprigs of 1.5 to 2 inch tubular, pale violet flowers, which are present from April to May. Paulownia is also grown in large plantations in the South for speculative wood exports toJapan.

Growth of paulownia is rapid, reaching up to 15 feet in a single year.  A single tree can produce approximately 21 million light, papery, wind-dispersed seeds.  These seeds will germinate almost anywhere they contact trace amounts of soil, including cracks on steep cliffs and spaces between pavement. Rapid growth and high seed production allow paulownia to easily crowd out native plant species and disrupt desirable forest regeneration after timber harvest or other disturbances.  Displacement of native plants destroys habitat for wildlife and can diminish opportunities for outdoor recreational activities such as hunting, hiking, and bird watching. If paulownia continues to proliferate through landscape planting and escape into natural areas, there will be significant economic impacts to the timber industry, agricultural production, and recreation.

In southern Ohio, paulownia commonly invades roadsides, riparian areas, forest edges, pasture, and disturbed forests. Continued planting of the tree as an ornamental has greatly expanded the area it is invading.  This spread is amplified by long range dispersal of seeds which can travel up to two miles in the wind.

Spring is a great time to identify populations of paulownia because of its showy display of flowers.  Leaves are heart shaped and velvety on both sides; attached opposite of each other along the stems; and can be up to 12 inches long and 9 inches wide, easily one of the bigger leaves found in the area.  Leaves look similar to those of catalpa trees, but catalpa leaves are only sparsely hairy on the upper leaf surface and are arranged in a whorl with three attached at the same position on the stem. Another characteristic that is distinctive for paulownia is the 1 to 2 inch green seed capsules that form during summer and split open in the late Fall.  These capsules will remain on the tree throughout the winter and are the best identification characteristic during the winter.

If the look of paulownia is what you desire in your landscaping and gardening, consider using these better alternatives: Northern catalpa (Catalpa speciosa), cucumbertree (Magnolia acuminate), or yellowwood (Cladrastis lutea).

Information for the control of paulownia can be found at www.ironfurnacecwma.org, or by contacting Eric Boyda at ericboyda@ironfurnacecwma.org.  Photo credit: James R. Allison.

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