University of Maryland Extension

CSI: The case of docile garden plant that runs amok! Or, Much Ado About Barberry

By Sara Tangren


People that like plants are generous by nature. Generous to a fault, in fact. In discussions with other gardeners, we are introduced to plants that we haven’t heard of before. And, one thing leads to another, and seedlings or divisions are shared. Everyone is happy…or are they?

You see, plant sharing goes beyond the garden fence. A plant species with seemingly docile growth tendencies in one climate and soil type, say on the Eastern shore of Maryland, can exhibit uncontrollable growth habits if it is shared with a gardener in an area that is geographically close but has a different type of soil, like in central Maryland. From there, progeny of the well-meaning gift can cross state lines, regional boundaries, and even national borders.

How does this happen, you ask?

Whenever another person gives us new information we evaluate it against our own life experiences. So when someone says Japanese barberry is invasive, we pause to think about our own personal experiences with barberry. These plants are available for purchase throughout the area, right? Surely businesses would not sell potentially invasive plants? Right?! You may have had this plant growing happily for the last 20 years without issue. So, what’s the harm in planting docile seedlings from Salisbury in Silver Spring?


A Master Gardener pulling barberry in Howard County that has escaped into the woods from the landscape

Most plant invasions begin quite modestly, with plants escaping from only a few gardens. With each generation they become a little better able to compete and spread in the wild. Eventually, in scattered areas of the country, isolated pockets of tough, competitive, alien, feral plants start to form. Eventually some of the isolated pockets come within cross-pollination distance of each other. This facilitates even more rapid adaptation and exponential increases in population size and distribution, and a full-scale biological invasion is underway.

Plant invasions are very patchy affairs. As more and more gardeners have first-hand experience, description of these plants will go from weedy to out of control to INVASIVE to THE PLANT ATE MY HOUSE!!!

Until the fall of 2013, when I started working at HGIC, I did most of my gardening and hiking in the Coastal Plain. When I began hiking the Piedmont parks in preparation for our native shade garden classes in 2014, I was shocked by the barberry problem. Nothing anyone had said to me about barberry had prepared me for that personal, first-hand experience. The sense of loss was indescribable. In particular I recall a hike through the Middle Patuxent Environmental Area, where as far as I could see in all directions, the forest floor was covered with a mix of barberry and multiflora rose. Every spring ephemeral was gone, every native fern gone.

Through the internet, we can now share our first-hand experiences using maps, photographs, blogs, videos, and especially social media. The map below shows how far Japanese barberry has spread since its introduction in the 1860s. Although 150 years is a very long time for any individual person, it is the mere blink of an eye in evolutionary time.

The fact is that by the time the invasion is so widespread that we've all seen it; only the most draconian measures could ever undo the damage.

Who remembers Smokey the Bear’s campaign “Only YOU can prevent forest fires”? When it comes to plant invasions, only YOU can prevent widespread plant invasion!

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