Berberis thunbergii DC (Zofnass Family Preserve)
Small shrub, ranging from 0.5–2.5 m tall. Stems armed with spines, with short shoots. Leaves obovate, 1.5–3 cm long × 1–2 cm, the margins entire, the upper surface green, the lower surface whitish. Inflorescences 1–4 cm long, with 1–4. Flowers 6-merous; petals cream-colored, with conspicuous yellow glands at bases; anthers opening by valves that bend upward. Fruits red.
Closely related species: Berberis vulgaris has serrate leaf margins and brightly yellow petals. The leaves of Berberis ×ottawensis, the hybrid between B. vulgaris and B. thunbergii, usually have some indication of leaf margin serrations.
Japanese barberry.
The related European species, Berbaris vulgaris (European barberry) , was introduced to North America by European settlers in 1875 as an ornamental and for preparing medicines, jams, and dyes from its fruits. It is the alternate host of the wheat rust caused by the fungus Puccinia graminis; thus, there was a major campaign to eradicate the European barberry in order to control damage to wheat caused by the rust. Berberis thunbergii, which is resistant to wheat rust, was introduced into North America from Japan to replace the European barberry. It has subsequently invaded the northeastern United States. As a result of these introductions there is the possibility of encountering European barberry, Japanese barberry, and hybrids between the two in the northeast, sometimes growing in close proximity. It appears that the hybrids are mostly the result of in situ hybridization and not the result of escape from cultivated hybrids (Connolly et al., 2013). However, all three with native plants and should be removed as soon as they appear.
Widely spread in the United States east to the Rocky Mountains, Washington, and southeastern Canada but does not occur in the southern states of the United States.
Grows in open disturbed areas and and in the understory of deciduous forests.
Flowers from April to May.
The red fruits are dispersed by birds.
Named after Carl Pehr Thunberg, a student of Linnaeus.
Not endangered in the NE United States.
Berberis thunbergii is an invasive species that can be easily recognized in the field by the following features: 1) a diffuse root system spreading out near the surface of the soil and a large taproot that penetrates deeply into the soil, 2) wood of the taproot bright yellow; 3) obovate leaves with entire margins, 4) spines arising from the stems, 3) cream-colored flowers; 4) conspicuous nectar glands at the base of the petals; 5) stamens that open with lateral flaps, and 6) bright fruits at maturity.
The Japanese barberry disrupts the life cycle of spring ephemerals and tree seedling by taking up space; blocking sunlight; and using nutrients and water that were claimed by native plants before this invasive species became a problem. The reason this species of Berberis is such a successful invasive is because it is one of the first understory plants to leaf out, using the same technique the spring ephemerals use to get a leg up on them. Individuals of this barberry are now such dominant plants that the understory in our area is colored barberry green in the spring, well before other plants flush their leaves.
Another reason for barberry’s success is that it has sharp spines to dissuade deer from eating the tender leaves. Without this protection there is a good chance spring flowers and seedlings will be nibbled to the ground by deer before producing flowers and seeds. Further, a very fine, diffusive system of roots branching from the tap root makes it possible for this plant to hog the nutrients needed for growth by other plant species. And common to many invasive plants, a barberry plant can fertilize the eggs in the ovules of its flowers with its own sperm, meaning that a single plant can start an entire population. Finally, the red fruits of barberries are efficiently dispersed by birds, allowing this species to spread far and fast. In short, barberry was already adapted for success when it was introduced from Asia.
Japanese and common barberries interbreed to produce hybrids called ×Berberis ottawensis which have been shown to produce some fertile pollen (Connolly et al., 2013). Studies are needed to determine if the hybrids are more or less prone to wheat rust and if they are more adaptable to the environmental conditions such as cooler weather or drier soil thereby enabling them to more agressively invade areas not yet colonized by their parents.
Although it would take an army of volunteers to get rid of barberry throughout its new range, it is possible to control this species at the local level. For example, plants can be eradicated in limited areas such as nature preserves by pulling them when they first arrive and then keeping them under control by ripping up new plants that periodically invade the area. Barberry plants are relatively easy to pull up, especially when small, but be sure to wear thick gloves to protect against spine punctures. The roots, which have bright yellow centers, are easily broken when they are larger, meaning that you must pull the tap root from the soil carefully if you want to avoid a new plant sprouting from it. This effort, while time-consuming, is well worth it–especially with research suggesting that the environment under and around barberry plants is preferred habitat for Lyme-carrying ticks.
There is hope that this forest enemy can be kept under control in nature reserves, but it would take many volunteers to make that happen. Sadly, the alternative—giving up and letting barberry plants grow where they can—has a greater cost: the continued disappearance of our spring wildflowers and tree seedlings. The most important thing to remember is pull up this and other invasives the first time they show up because older plants are difficult to remove and produce increasing numbers of fruits!