Japanese Barberry, Ticks And The Madman

It’s a perfect plant for the landscape. In the spring, it leafs out before other shrubs. It produces an abundance of red berries for the birds. Thanks to its thorns, it is deer resistant. It spreads easily and can form a dense barrier to keep animals or children in or out. And it requires very little care. What’s not to like about Japanese barberry (Berberis thunbergii)?

The things that make it a good plant actually make it a bad plant. And this plant is bad. Interestingly, it was introduced to replace a troublesome cousin, Common barberry (Berberis vulgaris).

Imported Hedgerow

Colonists had brought Common barberry to this country. It was commonly used to create hedgerow barriers for livestock and its berries made a great jam. However, the plant also served as a host for Wheat leaf rust (Puccinia triticina), a fungal disease that destroys grain crops. Massive eradication efforts successfully removed it from our cultivated landscape, although pockets do remain in the wild – especially where farmland has reverted to forest.

Japanese barberry was a good replacement for the now-banned European Common barberry. The Asian newcomer didn’t harbor wheat rust. But, as it turns out, it came with its own problems.

Humble Beginnings

Where to begin? This plant is so bad, we could start just about any place, but let’s explain how it became a problem in the first place. Boston’s Arnold Arboretum planted seeds in 1875. Twenty years later, Japanese barberry made its way to the New York Botanical Garden. It was quickly welcomed by the landscape industry and by the 1920s, it was a popular ornamental plant widely used in hedges and foundation plantings. Homeowners loved its early leaf-out and its bright red berries that would last into the winter. And that’s how the problem started.

How It Spreads

Humans weren’t the only ones to like those berries. Birds loved to snack on them and had a hand in scattering seeds far and wide. With a germination rate of over 90%, Japanese barberry sprouted everywhere.

And once a plant gets started, it doesn’t spread by seeds alone. It sends out clonal shoots below the ground to form new plants. And, if this isn’t bad enough, new plants will form when the tips of stems touch the ground and root, a process called layering. This all creates dense thickets of thorny plants.

A Dangerous Bully

Japanese barberry is tolerant of a variety of conditions from full sun to deep shade. It quickly colonizes an area, pushing out native plants such as the madman’s beloved spring ephemerals. Deer won’t eat Japanese barberry but will eat everything near it allowing for a faster spread. Severe drought and harsh winters have no effect on the plant. Researchers have found that its leaf litter changes the soil chemistry, raising the pH. They have also found that barberry thickets are attractive to non-native earthworms. As we have said in a previous blog, these earthworms quickly break-down the leaf litter layer on the forest floor, and this is not a good thing.

Public Health Issue

Still not convinced this plant is bad? Consider the public health issue raised by Lyme disease. We all know that Lyme disease is transmitted to humans by the Blacklegged tick (Ixodes scapularis), often referred to as Deer ticks. Scientists have discovered higher densities of this tick around Japanese barberry thickets than anyplace else. In fact, researchers at the Connecticut Agriculture Experiment Station (CAES) suggest that forests with Japanese barberry are 12 times more likely to harbor Lyme-infected Deer ticks. To understand why, we have to look at the life cycle of the Blacklegged tick.

The Deer Tick

The female Deer tick lays her eggs in the spring, usually around May. The larvae hatch out during the summer and look for a blood meal. At this point, they are disease free. They will become infected only if they feed on an infected host. Their favorite host is the White-footed mouse (Peromyscus leucopus). And guess where this little critter lives. In the dense thickets of Japanese barberry where it is protected from predators.

In the fall, the engorged larvae drop off the host and overwinter. As the weather warms in the spring, they return as nymphs, actively looking for another blood meal, preferably a large mammal which can easily be one of us (Gardenerii vulgaris). Peak time for these little buggers is late May through July. If previously infected, they can transmit the disease to their host. When they finish eating, they simply drop off and molt into an adult. In the fall, these adults begin to mate. Females look for large mammals for one final blood meal before they drop off to lay eggs the following spring. If the large mammal is an Eastern White-tailed deer (Odocoileus virginianus), the forest Uber, female ticks can be transported a far distance.

Don’t Blame The Deer

Deer are not the problem, the White-footed mouse living in his barberry castle with his guest the Black Legged tick is the problem. The White-footed mouse is the main natural reservoir for Lyme disease bacteria, infecting up to 90% of feeding ticks.

The mouse loves the safety that barberry offers, and the tick loves the free meal and thrives in the humid conditions of the barberry thicket. Researchers in Connecticut have shown that removing barberry thickets helps reduce the tick population.

War On The Japanese Barberry

So, the madman has officially declared war on Japanese barberry. He has always pulled the barberry near his walking path, but he has decided to actively seek out and remove any pockets that remain in the back. That could be quite a task because, once established, these thickets are hard to remove, and eradication efforts may take two to three years.

There are several methods for Japanese barberry removal. Whatever method you choose, make sure to protect yourself from the thorns and the ticks. Heavy work gloves, long pants and heavy boots are a must for thorn protection. But a chemical repellant with DEET, permethrin or picaridin will offer protection against the ticks. A few years ago, the madman discovered Insect Shield, a company that sells permethrin treated clothing that really works. It works so well that it has become his out-in-the-woods go to. But no control method works with 100% certainty, so we do extensive tick-checks at the end of each workday.

Your Choices

As we’ve said, there are choices in barberry removal – cut-back to the ground, complete removal, fire and chemical. With a sharp pair of Felco 8 pruners you may be able to cut back small patches to the ground. This will eliminate the shelter for the White-footed mouse and reduce the humidity for the tick. Be prepared to repeat the process several times before the shrub finally gives up and stops resprouting.

Burning the plant has also proved to be effective. With a propane torch, you can burn the plants down to the base. Be careful not to burn yourself or set the forest on fire. I refuse to let the madman borrow friend Bill’s torch.

Use Caution

Full-scale chemical spraying is best left to the experts or skipped entirely. But, you can use a cut-stump application of glyphosate or triclopyr if you apply the chemical immediately after cutting. This is most effective in the fall. Friend and fellow Master Gardener Tom Kalal uses the cut-stump applicator he purchased from PlayCleanGo. It makes application much easier and safer. The madman says it looks like a bingo dauber – now how would he know that?

Pulling or digging out the plant is the most labor intensive, but it does get rid of the plant. If you choose this method prepare yourself for some serious work. The roots aren’t deep, but they are so intertwined that they are difficult to pull. Many years ago, the madman bought an impressive puller called a Weed Wrench that has been useful for removing all sorts of plants. Although bulky and heavy it does work when the madman uses a lot of colorful language.

Neon And Moon

Recently he has learned of an exciting new method, actually it’s an old method with a revival. Friend Nancy Kalal has offered us the services of her team of oxen, Neon and Moon. She says all we have to do is attach the plant to the team and they will happily do the work. Nancy and her team are willing to travel and are looking for any pulling job you may have – you can find her at Cranberry Meadow Farm in East Lyme, CT.

The madman is not sure we have enough space to accommodate the oxen, but he’s willing to share his hot cocoa to find out.

Looks like we’ll be sharing some hot cocoa with Tom and Nancy. I wonder what oxen drink.