June 23, 2023
This the last installment of a four-part series on invasive plants and how they impact white-tailed deer herds and habitats. Truth is, there are hundreds of such plants, but I picked out what I call the “dirty four!” And I saved the one I despise the most for last — Common Barberry. This invasive was given the very appropriate Latin name, Berberis vulgaris! I have a particularly frustrating history with this plant at a place I managed for some time in New York. The entire understory of the property was dominated by this horrible plant, choking out almost every plant beneficial to wildlife.
Our options for control were very limited, due to local environmental protection regulations and the shear cost of removal. After years of trying, we finally gave up on control, substituting instead well-managed food plots. Common Barberry came to the U.S. from, you guessed it, Asia. It was imported primarily for fruit, hedges and dyes (yellow). There actually are two types of barberries that took hold in North America: Common and Japanese (Berberis thunberii).
Common Barberry came to the U.S. in the 1600s. By the 1900s, these plants had become a serious crop pest in wheat, because it harbored stem rust disease from grasses. Japanese Barberry then was imported around 1800, and it was supposed to be less problematic for harboring stem rust. Beginning in 1918, Minnesota began an eradication program for Common Barberry that was finally abandoned in the 1970s. In this program, millions of plants were destroyed, to no avail. By 2000, invasive barberries had become established in 21 states and four Canadian Provinces.
The “selling point” of Common Barberry from landscapers was the broad adaptability to soil types and conditions, as well as the attractive color and berries. The latter is one of the real problems with this plant — the berries are highly attractive to birds. Wild turkeys and ruffed grouse are also attracted to their fruit. Each plant can produce as many as 1,800 seed per year; and the plants are well- adapted to reproducing vegetatively through its fibrous root system.
Although broadly adapted site-wise, the one saving grace is that Common Barberry does not like wet feet or droughty sites. However, all other sites provide prime habitat. One of this invasive’s scariest adaptations is the ability to do well under closed canopy forests (my problem in New York). Many deer habitats in the eastern U.S. are dominated by old growth, closed canopy stands of hardwoods. There already is little browse for deer to eat under these impoverished conditions; then, Common Barberry chokes out the few quality browse plants in the understory.
Regarding white-tailed deer, there is little evidence of browse preference for Common or Japanese Barberry. To the contrary, both are marketed as “deer-proof” plants, making them even more attractive to homeowners and landscapers. There is reliable evidence, though, that high growth of barberries harbors ticks; and, in Connecticut, has been shown to relate to Lyme Disease! In fact, a Connecticut study showed that tick populations in barberry-dominated understories are 12 times higher than in native plant understories.
Yet another reason for me to dislike this species, the presence of thorns makes walking through dense stands almost impossible. This no doubt affects deer movements, as well. I think by now, you understand my disdain for this “champion” invasive plant species.
Have you noticed I have not used the term “eradicate” yet? As with the first three invasives in this series (Kudzu, Chinese Privet and Autumn/ Russian Olive), eradication of barberry is nothing but a pipe dream! There are the usual four control methods to be considered: biological, prescribed fire, mechanical and chemical. Grazing is totally out of the picture, since cattle will not even touch barberry. I am not familiar with many studies using goats, but the few available suggest they could be used in limited areas, where you can confine goats to force them to eat the shrubs. Other biological control options such as pathogens and herbivorous insects remain unknown.
In my battles with barberry in Upper New York forests, prescribed fire was a limited option; due to local restrictions and the high density of barberry plants in the understory. In these conditions, it is impossible to carry a fire through such a forest!
Some sources recommend individual treatment of plants using what we call in South Texas, a “pear burner.” This contraption is a propane tank connected to a torch that can be carried through the woods to burn individual bushes. This method of control is extremely time consuming. Besides, the heat only kills the above ground portion of the plant, which quickly sprouts back the next few months. Mechanical treatments such as mulching can effectively reduce the above ground portion of the plants at a reasonable cost; yet again, the plants quickly grow back. Mulching is accomplished using a large wheeled or track vehicle with a large grinder on the front, which can be raised and lowered to pulverize the plants at heights as great as 12 feet. The cost for this method usually runs between $150-$250 hour ($1,500 per day); and you can expect treatment of 2-3 acres per day in most areas.
Chemical treatment has shown promise in controlling barberry; yet it is a real testament to the toughness of this species that the most recommended chemical application is a mix of Glyphosate and Triclopyr! Glyphosate is a foliar spray, while Triclopyr can be applied both as a foliar spray and basal stem treatment. Together they can be formidable against barberry. However, there are issues such as environmental regulations and the logistics of spraying in heavily invested stands of barberry. However, there is no doubt the above mix will indeed kill barberry.
The best management approach is an integrated approach involving methods that are complementary. In this case, I feel reducing the above ground part of the plant by mechanical or burning methods, waiting for the plants to attempt to re-sprout, then applying a lesser amount of herbicide or fire would be the two best approaches. Either way, the cost in time and labor will be exceptional! As I have repeatedly noted, the best attitude for landowners and agencies to adopt is to NOT introduce new potentially invasive species.
The “horse is out of the barn” on many plants, including Common and Japanese Barberry. Yet, we still can learn to not repeat past mistakes. Remember, the next potentially harmful invasive species are still out there in the world, waiting for their opportunity. Don’t give it to them!