Wednesday, May 21, 2008

Landscape - Oriental Bittersweet, an Invasive Plant

The following is information on oriental bittersweet which has become an invasive plant that you want to control on properties where it has escaped. Information is from the University of Maryland.

Oriental bittersweet, Celastrus orbiculatus, often called Asiatic bittersweet, is a deciduous woody perennial plant which grows very prolifically in this area. A problem of nursery and landscape settings, this fast growing vine can grow as tall as fifty feet or more in one year, with a stem diameter of up to four inches. The leaves will be alternate, round in shape, with a finely toothed margin. Damage from this weed can be from breakage of the desired plant as it will grow into the canopy and create either weight or potential storm damage. The spirally habit can also choke other desired plants. Oriental bittersweet is very similar to American bittersweet, and can be distinguished by the location of the flowers and fruit. Berry location on the American bittersweet is only at the tips of the vines where with the Oriental bittersweet, the berries occur all along the vines.

Oriental bittersweet is an invasive plant. One reason for concern is the color and great numbers of berries produced. As birds are one of the prime methods of dissemination, a brighter red color is very attractive to the birds and with greater numbers of berries to be found, the potential of spread is much higher. To add insult to this problem, the seeds also seem to have a higher germination percentage than that of American bittersweet. Control of Oriental bittersweet can be accomplished through either mechanical or chemical means. Cutting near the base can be effective with small plants. As plants mature, the use of a stem application after cutting with the immediate use of triclopyr (Garlon 4) or glyphosate (Roundup and others) at a 25% solution. Use caution not to apply the herbicide to the desired plant material, as thin barked species can be damaged or killed. In open settings, where possible apply triclopyr and glyphosate. If possible mow the site first to create the cut stem. Repeated applications may be necessary. The use of a basal oil and a penetrant may be beneficial to increase the effectiveness. Use eye protection when doing stem applications, as some products are salt based and may cause eye damage.

Information from Chuck Schuster in the May 9, 2008 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.

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