Chinese Ligustrum, an Invasive Menace
Amiable Spouse finally agreed to cut down the variegated Chinese privet that was growing in the front yard. I pruned it back countless times and was always careful to cut out the portions that had reverted to solid green. Still, he rather liked it, but he acquiesced after I explained the problem and showed him evidence of reversion to solid green in several places in our neighborhood.
I felt it was my responsibility as an environmentally conscious gardener to ask for the variegated shrub to be removed. Although it is not the green form that can be seen mile after mile along the fencerows and woods’ edges in the South, they still present a threat. According to Michael Dirr
, and evidenced by my own eyes, the variegated form is capable of producing seeds. When these seeds germinate, they do not give rise to the pretty variegated form. Solid green seedlings emerge, and it is this form that is such a menace.
Many of my neighbors have the variegated form of Chinese ligustrum (Ligustrum sinense) in their yards. Almost everyone will agree that it makes an attractive contrast in color when planted among dark green shrubs in the landscape. A visit to a nursery will tempt unwary customers to purchase the attractive plant. Several attractive cultivars have been developed. Buyer, beware! Just down the street, I see instances where more than half of a variegated shrub has reverted to solid green. These solid green stems bear hundreds of berries that are carried as far away from the plants as birds can fly.
A member of the olive family (Oleaceae), this plant was introduced in the United States as an ornamental in 1852. By 1933 it had become naturalized, and not long afterwards it was recognized for the noxious weed it is. Maturing to about 12 feet tall and wide, the shrub is hardy to Zone 6. Ability to grow in sun or heavy shade in either wet places or drier upland sites makes it adaptable to a wide range of growing conditions. It is a quick invader of disturbed sites and can even grow in the crack of a sidewalk. Capable of forming dense, impenetrable, monocultural thickets, the shrub can dominate the shrub layer of an invaded habitat and alter the ecosystem by choking out native plants.
I fought the Chinese ligustrum for years in Mississippi along the fence rows and woods’ edges of Daddy’s pastures and gardens. A drive along almost any highway or byway in the southern United States reveals mile after mile of Chinese ligustrum. Daddy called it privet, and I am told that in the late 1800s, my grandparents and their neighbors planted it in their landscapes as an ornamental shrub. Little did they know the consequences of their actions.
When A. Spouse and I visit his daughter in rural Florida in April and May during the bloom season, I have a difficult time breathing. The flowers are pretty enough with white terminal and axillary clusters lined most of the way up the stems. The overpowering scent emanating from them, however, is absolutely smothering for me. Not only can the scent of the flowers trigger allergic reactions in odor-sensitive individuals, but the pollen can cause respiratory irritation, as well.
Almost all states within its range list Ligustrum sinense as an invasive plant. Mississippi State University lists it as one of Mississippi’s ten worst invasive weeds. The Georgia Exotic Pest Plant Council also has it on its top ten, and the Florida Exotic Pest Plant Council lists it as a Category I exotic invasive plant. Tennessee and Kentucky list it as a severe threat, and it is on Virginia’s list of highly invasive plants. Texas, Alabama, North Carolina, and South Carolina, have placed Ligustrum sinense on an exotic invasive list of some type. Herbarium records show current distributions extending from Florida to southern New England and westward to the eastern parts of Texas, Kansas, and Oklahoma.
Other species of ligustrum are also problematic and appear on the list of invasive plants in various states. It might be wise to be wary of these other species, as well, including the highly ornamental and frequently grown Ligustrum japonicum (Japanese ligustrum). Other species frequently listed are L. lucidum (glossy privet), L. obtusifolium (border privet), and L. vulgare (European privet). Check lists of invasive plants in your area to see if any of these species are listed.
Conservation begins at home, just as, according to Charles Dickens, charity does. Plants can be controlled by hand removal if the stems are less than one inch in diameter. Be sure to remove the entire root because any pieces left will sprout. Foliar applications of glyphosate (Roundup or Finale) will kill the plants, but be careful; the chemical also kills any plants around it. The plants can be cut and stump killer applied to the stump immediately afterward.
The best course of action might be to simply avoid this genus of plants. Do not purposely plant one in your landscape if it is listed as an invasive in your area, and if one appears, remove it immediately. Continue to share with others the dangers inherent in all invasive plants, and with persistence and resolve, we may be able to make a difference in the health of the environment in some small way. After all, we have to start somewhere. At home seems the logical place.
Mouse over pictures for explanations. Thanks to Debin SC for the image of Ligustrum