Sadly, many cultivars of this plant should no longer be grown. The problems with Japanese Barberry include:
(1) Invasiveness. Since the 1980’s, barberries have become a major pest and are outlawed in several states. Many of our barberry cultivars produce abundant amounts of fruit and seeds. The fruit are not especially attractive nor nutritious to wildlife. The red berries will hang on the shrubs until late in the season. When there is no other food available, birds and small mammals consume the fruit and carry it into our woodlands. There, with often a 90% or greater germination rate, the seeds sprout. As the plants grow, new shoots spring up from the shallow roots. Whenever a branch gets long enough, it touches the soil and takes root. Soon there is a huge and impenetrable thicket of barberry. In Connecticut, there are huge areas with dozens of acres carpeted with aggressive barberry plants. Native plants are shaded out. Food for wildlife is reduced. Since deer will not eat barberry, native orchids, trilliums, and other desirable woodland wildflowers are nibbled to death by the hungry deer. At least 20 states have declared Japanese barberry to be an invasive plant.
(2) Prime hiding spot for Deer-ticks and rodents. The barberry bush, with its arching branches, provides shelter from predators and weather. Mice nest in their barberry home. Ticks love the high humidity micro-climate under these bushes, and the mice provide the blood needed for the baby tick meals. Adult ticks attach to passing deer. Studies have shown a higher number of Lyme disease-infected ticks in barberry patches; a barberry patch can host up to 120 Lyme disease-carrying ticks per acre and without barberry, only 10 diseased ticks. In recent years the incidence of Lyme disease has increased, and it is now a major public health concern.
(3) Soil disruption: Barberry roots can change the soil microbiology and chemistry. Nitrate concentrations increase. The excess nitrogen in the soil can leach into the nearest waterway or water table. Organic matter is also rapidly depleted by Japanese barberries. The altered soil chemistry can attract more invasion by other weedy plants. When the barberries are removed, the soil chemistry disruptions are believed to persist for a while, making restoration of desired native plants more difficult.
(4) Non-native earthworms: Native earthworms in Minnesota died out during the most recent Ice Ages. Non-native European earthworms were brought here accidently. They are helpful in aerating our gardens and breaking down compost, but in a woodland setting, they consume leaf litter needed by woodland plants to thrive. After the leaf litter is consumed, gulley erosion starts, soil washes into waterways, and the soil chemistry alters. Earthworm populations are increased in barberry thickets. If barberry is controlled, earthworm populations decrease.
According to the Minnesota Department of Agriculture, there are Japanese barberry cultivars that are Restricted Noxious Weeds. These weeds are defined as “plants that are widely distributed in Minnesota and are detrimental to human or animal health, the environment, public roads, crops, livestock or other property, but whose only feasible means of control is to prevent their spread by prohibiting the importation, sale, and transportation of their propagating parts in the state except as allowed by Minnesota Statutes” (Minnesota Department of Agriculture).
According to the Minnesota Department of Natural Resources:
“These cultivars average greater than 600 seeds per plant and cannot be sold in Minnesota:
‘Angel Wings’; ‘Antares’; var. atropurpurea; ‘Bailtwo’ (Burgundy Carousel® - ‘Monomb’ (Cherry Bomb™); ‘Crimson Velvet’; ‘Erecta’; ‘Gold Ring’; ‘Bailsel’ (Golden Carousel® - B. koreana × B. thunbergii hybrid); ‘Inermis’; ‘Bailgreen’ (Jade Carousel®); ‘JN Redleaf’ (Ruby Jewel™); ‘JN Variegated’ (Stardust™); ‘Kelleris’; ‘Kobold’; ‘Anderson’ (Lustre Green™); ‘Marshall Upright’; ‘Painter’s Palette’; ‘Pow Wow’; ‘Red Rocket’; ‘Rose Glow’; ‘Bailone’ (Ruby Carousel®); ‘Silver Mile’; ‘Sparkle’; ‘Tara’ (Emerald Carousel® - B. koreana × B. thunbergii hybrid); Wild Type (parent species – green barberry).”
Minnesota already has barberry infestations in southeastern Minnesota along the Mississippi, the Arrowhead region, and west of the Twin Cities. 25 varieties of Japanese barberry have been phased out and their distribution and cultivation are illegal. I doubt if the plant police will come after you, but gardeners are encouraged to replace Japanese barberry with other plants. Alternative plants include purple-leaved weigela cultivars, ninebarks, shrub roses on their own roots, winterberry holly, dwarf fothergilla, New Jersey tea, Virginia Sweetspire, and Aronias.
A small colony of barberry can be removed by digging out the plants and as many roots as possible. Larger infestations are controlled by cutting and applying brush killer, using a propane weed torch, or with prescribed burning. Reading and understanding the pesticide label, and following directions are important when using herbicides. Training, proper permission, and water hoses are needed if a propane torch weed burner or a larger controlled burn is used for control. Repeat removal may have to be done every five years, if new plants sprout.
The University of Connecticut has an excellent three-part video series about Japanese barberry and Lyme disease that should be of interest to all gardeners:
Part 1. The Trouble with Barberry, https://www.youtube.com/watch?v=ehN-QTPqSDQ
Part 2. Controlling Barberry, https://www.youtube.com/watch?v=O9XWaCtJDiU
Part 3. All about Lyme Disease, https://www.youtube.com/watch?v=6TT7Q3VXfQQ
Sorry to shed bad news about a favorite plant.
I still wish all of you, Happy Gardening,