Authors: Mandy Tu, Global Invasive Species Team, The Nature Conservancy
- Paulownia tomentosa is a medium sized tree (50-60 ft. [15.2-18.3 m] in height and 2 ft. [0.6 m] in diameter) that can commonly be mistaken for the native tree northern catalpa (Catalpa speciosa). Bark is gray-brown and rough, often developing lighter-colored shallow vertical fissures.
- Leaves are large, broadly oval to heart-shaped (6-12 in. [15.2-30.5 cm] long, 5-9 in. [12.7-22.8 cm] wide) and arranged opposite along the stem, hairy on both surfaces. Petioles are also hairy and can be sticky when young. Leaves growing off root sprouts have been measured up to 2 ft. (0.6 m) in length. Twigs are stout, brown, and speckled with white dots (lenticels). They can be slightly hairy when young. Lateral leaf scars are somewhat round, becoming darker and sunken. The pith is chambered or sometimes hollow.
- Large flowers (2 in. [5.1 cm] long) are fragrant and light violet-pink, appearing in showy upright clusters (8-12 in. [20.3-30.5 cm] in length) in early spring (April-May) before leaves emerge. They have tubular corollas, ending in 5 unequal lobes. Flower buds are hairy and linear, becoming round.
- Fruits (1-2 in. [2.5-5.1 cm] long, 1-1.5 in. [2.5-3.8 cm] wide) are egg-shaped capsules, divided into 4 inner compartments that contain the seeds. Fruits are light green in the summer, becoming dark brown in the winter, and persist in clusters on the tree until the following spring. The capsules split in half during late winter to release up to 2000 tiny winged, wind-borne seeds 0.08-0.12 in. (2-3 mm).
- Ecological Threat
- Paulownia tomentosa is an aggressive tree that invades disturbed natural areas including forests, roadsides, and stream banks. It is native to China and was first introduced into the United States as an ornamental in 1840.
Paulownia tomentosa can be controlled most effectively using an integrated management approach. Cutting or girdling trees with power or manual saws are effective at preventing seed production, but repeated cutting or a herbicide treatment is necessary following cutting since Paulownia readily resprouts.
Young seedlings of Paulownia can be successfully controlled by manual removal. Pulling is easiest following a rain event, as the soil becomes loose. It is important to remove all root fragments as Paulownia can resprout from root fragments.
Cutting and Girdling
Cutting of Paulownia trees is most effective at the onset of flowering. Cutting at ground-level can prevent seed production for that year, but cutting alone must be repeated for several years to successfully kill the tree. Girdling results in top-kill of that stem, but may also induce increased resprouts. Cutting and girdling followed immediately by a herbicide application (cut-stump, hack-andsquirt) has good rates of efficacy.
Paulownia can successfully be controlled by herbicides. The most common herbicides used to control Paulownia include glyphosate (tradenames RoundUp®, Rodeo®) and triclopyr (Garlon 3A® or Garlon 4®).
Paulownia seedlings can be controlled by using a foliar spray of either glyphosate (2% solution with 0.5% nonionic surfactant) or triclopyr (2% solution with 0.5% nonionic surfactant). These spray herbicides should be applied directly to the leaves and sprayed-to-wet.
Following cutting of the trees at ground-level, glyphosate (25% solution) or triclopyr (50% solution) should be directly applied to the stump. The cut-stump method can be used at all times of the year, as long as the ground is not frozen.
Girdling or Hack-and-Squirt
Immediately following girdling (approximately 15 cm above the ground and the cut should be well into or below the cambium layer) or hacking, directly apply glyphosate (25% solution) or triclopyr (50% solution) into the cut area.
Apply a mixture of 25% triclopyr and 75% horticultural oil to the basal parts of the tree to a height of 30-38 cm (12-15 in) from the ground. Thorough wetting is necessary for good control, and spray until run-off is noticeable at the ground line. Basal bark applications should not be applied when the ground is frozen.
- Innes, Robin J. 2009. Paulownia tomentosa, Fire Effects Information System, U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory
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- Virginia Tech Department of Forest Resources and Environmental Conservation
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