Japanese Barberry (EwA Guide to Common Invasive Species in Middlesex County (MA, US) )

Japanese Barberry

Berberis thunbergii

Summary ⁷

Berberis thunbergii, the Japanese barberry, Thunberg's barberry, or red barberry, is a species of flowering plant in the barberry family Berberidaceae, native to Japan and eastern Asia, though widely naturalized in China and North America, where it has become a problematic invasive in many places, leading to declines in species diversity, increased tick habitat, and soil changes. Growing to 1 m (3 ft 3 in) tall by 2.5 m (8 ft 2 in) broad, it is a small deciduous shrub with green leaves turning red in the autumn, brilliant red fruits in autumn, and pale yellow flowers in spring.

Short Description ⁸

Perennial, deciduous shrub, usually with many branches. The leaves are simple, alternate, entire, and small, with tapered bases and rounded ends. Occur in groups starting from nodes along the twig. A sharp spine is visible at the leaf axil. Flowers are small yellowish, have six petals, and hang below the stem. Fruits are elongated red berries that hang below the stem.

Source: EwA Invasive Pocket Fieldguide | © Earthwise Aware

Description ⁷

B. thunbergii has deeply grooved, brown, spiny branches with a single (occasionally tridentine) spine (actually a highly modified leaf) at each shoot node. The leaves are green to blue-green (reddish or purple in some horticultural variants), very small, spatula to oval shaped, 12–24 millimetres (1⁄2–15⁄16 in) long and 3–15 millimetres (1⁄8–9⁄16 in) broad; they are produced in clusters of 2–6 on a dwarf shoot in the axil of each spine. The flowers are pale yellow, 5–8 millimetres (3⁄16–5⁄16 in) diameter, produced in drooping 1–1.5 centimetres (3⁄8–5⁄8 in) long umbrella-shaped clusters of 2–5; flowering is from mid spring to early summer. The edible fruit is a glossy bright red to orange-red, ovoid berry 7–10 millimetres (9⁄32–13⁄32 in) long and 4–7 millimetres (5⁄32–9⁄32 in) broad, containing a single seed. They mature during late summer and fall and persist through the winter.

Identification ⁷

This species is sometimes confused with Berberis canadensis (American barberry), Berberis vulgaris (common or European barberry), and other deciduous Berberis species; it is most readily distinguished by the flowers being produced in umbels, not racemes.

Invasiveness ⁷

Japanese barberry can be found in most northeastern and Great Lakes states of the United States. A current map of its distribution can be found at the Early Detection and Distribution Mapping System (EDDmapS). In recent years, Berberis thunbergii has been recognized as an invasive species in many parts of the eastern United States. The Plant Conservation Alliance's Alien Plant Working Group lists it among its "Least Wanted". Japanese barberry is prohibited from being a seed contaminant in Michigan and banned from sale in Massachusetts and West Virginia. This species is ranked "Very High" on the New York State Threat Assessment scale.

This Berberis is avoided by deer, and has been replacing native species. Furthermore, the plant can raise the pH of the soil and affect soil nitrogen levels. Unlike B. canadensis and B. vulgaris, B. thunbergii does not act as a host for Puccinia graminis (black rust), a rust pathogen of wheat. B. thunbergii, however, naturally hybridizes with B. vulgaris, and the offspring can be susceptible to P. graminis.

Japanese barberry provides an exceptionally favorable environment for ticks due to the high humidity present in barberry's dense foliage. It is hypothesized that spread of barberry is correlated with the spread of Lyme disease. Tick numbers are higher in areas with thick barberry understories, as opposed to areas with controlled barberry or no barberry. In one study, 280 ± 51 adult black-legged ticks, Ixodes scapularis, were found per hectare (113 ± 21/acre) in a barberry infected area, while only 30 ± 10 adult black-legged ticks were found per hectare (12.1 ± 4.0/acre) in otherwise similar area with no barberry present.

Detailed information on how to control Japanese barberry is available in a Michigan Department of Natural Resources document.

⭕ Control Methods (EwA Content) ⁹

Small infestations of Japanese barberry may be managed only through mechanical methods like pulling and digging, particularly in shaded areas with shallow-rooted, less robust plants (b). Combining mechanical and chemical methods works best to effectively control medium to large Japanese barberry infestations (a). Typically, the treatment begins with mechanical methods followed by chemical treatments (a, b). Prescribed burning can also help control Japanese barberry but should be part of an integrated management plan (b).

Mechanical Treatment

Pulling and digging → In small infestations, pull seedlings and small plants, pulling out their shallow roots. Do it when the soil is moist, pilling slowly and steadily to reduce soil disturbance and use gloves to shield hands from stem spines (b, d). While pulling, preserve the root crown as much as possible; any remaining in the ground may resprout. Use tools like a weed wrench or a root talon to handle medium-sized plants. Spades work for larger plants, but after removal, carefully compact the disturbed soil and cover the treated area with leaves for added soil protection (b).

Cutting and mowing → Cutting alone is the least effective control method because they will resprout once you cut them (c, d). Mowing can deter seedling establishment and, when done repeatedly, can curb the spread (d). However, because the plant resprouts from the root crown, it's essential to combine mowing with other methods for adequate control. Treating resprouts with herbicide or carrying out prescribed burning later in the season enhances control and manages regrowth more effectively (b, c).

Prescribed-burning Treatment

Prescribed fire is effective for Japanese barberry control in fire-adapted ecosystems (b). A propane torch (flame-weeder) works well in spring, and follow-up treatments during summer to address survivors (d). When there's ample fuel, late spring burns excel at eliminating seedlings, while repeated fires over the years target mature plants (b). Aim for a 10-20 second "blast" on each side of the clump, heating until stems begin to glow (c).

Combining fire with other treatments yields faster results. It can be integrated at different stages: Burn to target resprouts after cutting or mowing, or apply fire first, followed by herbicide for resprout treatment (b). Alternatively, start with herbicide and then burn resprouts. Ensure compliance with state regulations and requirements before planning and conducting prescribed burns (b).

Chemical Treatment^⚠

Herbicide treatments are very effective, and different treatments can be employed as part of a suitable control plan (b). Apply foliar treatments in spring (while native species have not yet leafed out) or late Fall (when native species are already dormant); this can help to minimize damage to native species. However, the timing for application varies depending on the product to be used (b, d). Cut-stump applications are possible but not ideal due to the numerous small stems of the species (d).

Foliar treatment → For sites with dense infestation of Japanese barberry and limited native vegetation, foliar treatment using glyphosate or triclopyr is ideal (b, c). To manage taller, hard-to-reach plants, use a combination approach: cut them in the first year and apply foliar herbicides in the second year (d). To prevent harm to desirable vegetation, spray herbicides only at the start and end of the growing season when native wildflowers and seedlings are primarily dormant (c). Avoid herbicide use during stressful periods like drought, as it may reduce effectiveness. It is also ineffective to apply herbicides during significant sap flow when plants are actively growing (b).

Do not use glyphosate in early spring while plants are still leafing out; leaves will not absorb enough product. Triclopyr can be sprayed on leaves from spring (once plants are fully leafed) to fall (before they change color) (b).

Cut-stump treatment → Cut-stump applications are suitable in all seasons except during heavy spring sap flow (b). Apply herbicide immediately after cutting using tools like a brush, spray, wicking applicator, or squirt bottle (b, c). Monitor treated plants for at least a year; cut and retreat or use the foliar spray on resprouts. Consider product labels and recommendations, as some products are less effective in lower temperatures or when plants are dormant (b, c).

Glyphosate is more effective in cut surface treatment when plants are fully leafed and growing actively. Triclopyr is effective throughout the year, but the control may be reduced in early spring or drought periods in summer (b).

Disposal

Dispose of pulled seedlings and shrubs in a way that ensures the roots dry totally. For fruit-bearing plants, burn or bag them for disposal (b). Verify state regulations to confirm landfill disposal eligibility.

⚠ Disclaimers

Disclaimer #1: Harmless chemicals do not exist. Any chemical use is likely to harm non-target species and affect the soil. However, in some circumstances, chemicals might be the only way to succeed in removing an invasive species permanently. In all cases, researching and understanding the latest scientific literature before using a specific chemical or a mix of several is critical to reducing negative impact.

Disclaimer #2: Independently, several European countries recently announced future bans or massive restrictions on the use of glyphosate (e.g., Austria, Germany, France). The EU, at large, is expected to decide on the renewal of the approval of glyphosate Ultimo 2023 (More here).

Sources

[a] - Japanese barberry. Available in: https://www.mda.state.mn.us/plants/pestmanagement/weedcontrol/noxiouslist/japanesebarberry
[b] - Japanese barberry - Michigan Department of Natural Resources Michigan Natural Features Inventory 2/2012. Available in: https://mnfi.anr.msu.edu/invasive-species/JapaneseBarberryBCP.pdf
[c] - Japanese barberry control methods. 2013; Available in: https://portal.ct.gov/-/media/CAES/DOCUMENTS/Publications/Special_Bulletins/SpecialBulletinFeb2013Wardpdf.pdf
[d] - Japanese Barberry, Berberis thunbergii. 2019; Available in: https://www.maine.gov/dacf/mnap/features/invasive_plants/berberis.htm

Sources and Credits

(c) Claire O'Neill, some rights reserved (CC BY-NC), uploaded by Claire O'Neill, https://www.inaturalist.org/observations/113205269
(c) Bill MacIndewar, some rights reserved (CC BY-NC), uploaded by Bill MacIndewar, https://www.inaturalist.org/observations/114451064
(c) Claire O'Neill, some rights reserved (CC BY-NC), uploaded by Claire O'Neill, https://www.inaturalist.org/observations/100872792
(c) Jennifer Clifford, some rights reserved (CC BY-NC), uploaded by Jennifer Clifford, https://www.inaturalist.org/observations/49603092
(c) Ale E., some rights reserved (CC BY-NC), uploaded by Ale E., https://www.inaturalist.org/observations/98206813
Adapted by Claire O'Neill from a work by (c) Wikipedia, some rights reserved (CC BY-SA), https://en.wikipedia.org/wiki/Berberis_thunbergii
(c) Claire O'Neill, some rights reserved (CC BY-SA)
Adapted by Esther Meirelles from a work by (c) Claire O'Neill, some rights reserved (CC BY-SA)

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