Is This The Future of Invasive Plants?

Yellow-leafed Japanese barberry . Photo courtesy of

Yellow-leafed Japanese barberry . Photo courtesy of

I recently heard Dr. Mark Brand from the University of Connecticut speak about his work evaluating cultivars of Japanese barberry (Berberis thunbergii)an invasive plant species.  For over a decade, Dr. Brand has been studying and assessing the invasive potential of different cultivars to determine whether or not the entire species should be banned here in Connecticut, or if some of the cultivars are, essentially, seedless and therefore will not become invasive. Brand has also used the knowledge gained from his work to breed several new compact sterile cultivars of Japanese barberry.

I can hear some of you saying…hold on…who cares if the entire species if banned? And why on earth would we want to promote the landscape use of any cultivars of a plant like Japanese barberry? How do we know that these cultivars aren’t cross-breeding with the species? Have we learned nothing from past experience?

A Different Path

Unlike many states, Connecticut decided against an outright ban of Japanese barberry and instead growers agreed to voluntarily ban 25 Japanese barberry cultivars, based in large part on Dr. Brand’s initial research findings. Admittedly, this voluntary ban is somewhat self-serving for growers. According to the Connecticut Nursery and Landscape Association, the revenue from the 25 banned cultivars in Connecticut alone is over $5,000,000 annually. I couldn’t find figures on the revenues from Japanese barberry cultivars still on the market, but I imagine the number is also quite high.

It’s All in The Genes

I’m not a scientist, nor do I play one on this blog.  While I understand the basic science behind Dr. Brand’s work, I am in no position to defend it. Having said that, I can tell you that Brand and his colleagues used AFLP marker technology to look at genetic markers in stands of invasive Japanese barberry at different sites near UCONN to determine its origin and to see if wild populations could be linked genetically to cultivars.  In essence, are cultivars planted in our home landscapes ‘escaping’ into nearby wild areas.

Brand found a large Crimson Velvet plant produces over 5,000 seeds each year.  Image courtesy of  John Ruter, University of Georgia,

Brand found a large Crimson Velvet plant produces over 5,000 seeds each year. Image courtesy of John Ruter, University of Georgia,

Brand’s team found seed production in cultivars of Japanese barberry varies radically. For instance, Golden Devine (Berberis  thunbergii ‘Golden Devine’) has no seeds while one Emerald Carousel (Berberis thunbergii ‘Tara’) shrub had almost 10,000! In general, Brand found that tall green-leaved cultivars tend to produce copious amounts of seed while compact yellow or purple-leafed cultivars tend to produce the lowest amount of seeds.

Based in part on germination rates (15 – 30%) and seedling survival rates (10 – 20%), Brand determined Japanese barberry cultivars with 50 or fewer seeds per plant can be considered non-invasive. He also found plants really need to be evaluated for a much longer time frame than is typically done by growers to accurately determine seed production. Evaluating cultivars for seed production, or sterility, after only a year or two can be misleading. Brand’s team tested cultivars in landscape situations for almost a decade and found seed production often increased, sometimes dramatically, as plants matured.

The Wave of the Future

Whether you agree with Connecticut’s approach to dealing with Japanese barberry (Berberis thunbergii)  or not, this science-based approach to evaluating cultivars of invasive species, rather than painting them all with the same broad brush, may be the future of dealing with invasive plants.

Some states are already beginning to follow Connecticut’s research driven approach to regulating invasive plants. Recommendations from Minnesota’s Noxious Weed Advisory Board specifically reference Connecticut’s methods. In Oregon, a state known for its strict invasive plant policies, several new ‘sterile’ cultivars of butterfly bush are being sold after years of an outright ban on the species. Is this progress or a step in the wrong direction?

Through his research, Brand found that when breeding new cultivars of Japanese barberry, mixing together three different species virtually eliminates seeds in cultivars. UCONN hopes to introduce six sterile cultivars of Japanese barberry in the near future. Breeding is also being done by Dr.Thomas Ranney at NC State University. So whether you’re on board or not, it’s time to get ready for the arrival of sterile cultivars of Japanese barberry in your local nursery.

A sea of Japanese barberry at a local wholesale nursery.

A sea of purple-leafed Japanese barberry at a Connecticut wholesale nursery.

Frankly, I’m not entirely sure how I feel about these potential seedless Japanese barberry cultivars. In an ideal world, I’d like to see an outright ban of Japanese barberry here in Connecticut. But regulation based on empirical data appeals to the pragmatist in me. Still, I’m worried about the coulds and what ifs. Research has also shown that some exotics lay low in the landscape for years before becoming invasive. On the other hand, one of the realities of today’s economy is that funding for some state invasive plant programs is disappearing. Will these sterile interspecific hybrids mean that once condemned invasive plants find new homes in our landscapes?

Education is an important component to the problem of invasive plants and helping gardeners find native plant alternatives to invasive plants is a key to dealing with the problem, even as sterile hybrids begin to find a place in local nurseries. 

© 2014, Debbie Roberts. All rights reserved. This article is the property of Native Plants and Wildlife Gardens. We have received many requests to reprint our work. Our policy is that you are free to use a short excerpt which must give proper credit to the author, and must include a link back to the original post on our site. Please use the contact form above if you have any questions.

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  1. says

    I appreciate this objective presentation of what can be a quite emotional debate. My response here is the same as in so many landscaping discussions: it’s all about self-interest. Who benefits from this expensive research? It seems to me that if the main effort in the research is to eliminate Barberry seeds, then creating healthy ecosystems is not part of the equation. So who benefits? Nursery growers, landscapers, the university itself, and gardeners who want to keep using the same plants they’ve always used and thinking the same way they’ve always thought. This is another sad example of how the landscaping and gardening industries, and the majority of Americans, feel free to bully nature around to serve our own rather shallow self-interests.

    • says

      God Sue, I so agree with you, and I can’t count how many “pros” I’ve pissed off and will continue to piss off saying something similar as you. “Feel free to bully nature around to serve our own rather shallow self interests.” Exactly. This is what I want, it’s always been like this, I’m used to it, I’m a free American so stop making me feel bad you righteous purist nutzo. Now where’s my V-8 truck loaded with plastic mulch.
      Benjamin Vogt recently posted..Teaching Gardens: Aesthetics, Ecology, & Climate Change

  2. says

    Sue, You’re so right, it’s all about self-interest and often nature seems to be on the losing end of the equation. And this presentation was definitely skewed towards an audience of primarily growers and nursery owners. I do find it interesting that Dr. Brand’s research was funded in part by the CT Nursery & Landscape Association and in part by the NE Native Plant Center. Dr. Brand’s lecture was followed by one given by Dr. Lubell, also from UCONN, on native alternatives to invasives. I’m planning to write about that next but I can tell you that Dr. Lubell was making an excellent case to the same audience to start growing/selling some underused natives that are being trialed side by side with invasive in test plots at UCONN. In fact, after her presentation I was talking to the owner of one of the major growers in CT and we both had written down the name of a native we’d never heard about – Diervilla lonicera. I asked if his wholesale nursery sells it and he said he wasn’t sure but was certainly going to look into it. I consider that progress.
    Debbie Roberts recently posted..Wordless Wednesday ~ Silhouette

    • says

      Yes, Diervilla lonicera is a lovely native that occurs naturally in a pretty huge region covering all of New England, the upper Midwest and southern Canada. I’ve used it for years. Many different pollinators LOVE it, and the mid-summer blooms are especially appreciated – by people and pollinators. Plus it has gorgeous fall color, deep burgundy, and is a wonderful blender with hay-scented fern, interrupted fern, sweetfern, rubus species and a variety of spring wildflowers (wintergreen, trailing arbutus, Indian cucumber, etc.), all plants with which it naturally grows in the wild. It is, however, what a lot of people might consider “messy” and would probably not be appreciated in a bed that’s supposed to look tidy. It’s really great, however, in semi-wild conservation patches or wildlife hedges and corridors.

      • says

        Sue, Thanks for the overview of Diervilla lonicera and the list of companion plants. After a little research I’d agree that it probably is not one of the native plants that will be embraced by every gardener, but that’s OK. I love that people are out there advocating for it’s use, along with other lesser-known natives. I’ll definitely put it on my wish list for my own garden.
        Debbie Roberts recently posted..Wordless Wednesday ~ Silhouette

  3. Ann Astarita says

    Thank you for the concise review of the barberry cultivar issue. I’m skeptical about the value of spending time and money trying to create sterile barberry cultivars. In my opinion, we should focus instead on plants native to our region which we know provide essential habitat for pollinators, songbirds and more. The exotic, the new, the showy non-native plants too often prove lacking and even detrimental when it comes to long-term ecosystem health.

    • says

      Ann, I can appreciate your skepticism but it’s a reality that a lot of $ is being spent on these types of projects. While I would certainly like to see more focus on native plants, I am pleased to see that plant breeders are beginning to focus on more than just rushing the next new cultivar to the market. I really believe the answer to long-term ecosystem health needs a multi-pronged approach and the use of native plants is one part of the equation.
      Debbie Roberts recently posted..Wordless Wednesday ~ Silhouette

  4. says

    This discussion doesn’t touch on the other part of need to use native plants. Wildlife! I haven’t searched for it, but I’d bet the barberries don’t support anything like the number of pollinators, birds, etc. that some of the alternately recommended natives do, e.g. Fothergilla, Itea virginica, Cephalantus, et al.

    • says

      Hi Lloyd, You’re correct, I did not bring the wildlife value of Japanese barberries into my post and that was on purpose. The intent was to look at the work being done with breeding invasive plant cultivars and how it is already affecting public policy. I wholeheartedly agree with you that from a wildlife/ecosystem perspective, there are a plethora of better options out there than Japanese barberry and you’ve mentioned some of them. I’d also add Clethra, Physocarpus, Vaccinium and Aronia. Thanks for getting the native alternatives list started!
      Debbie Roberts recently posted..Wordless Wednesday ~ Silhouette

  5. says

    I was at the CNLA conference a few years ago when the growers/attendees started a game “throwing” Berberis thunbergii as a promise not to grow it anymore. Whomever threw it the farthest won the game and it was a fun experience to see. However as I watched this, I was thinking about all the natives we could be growing instead of wasting time researching sterile cultivars. Glad to see others felt the same!
    Diane S recently posted..What To Do with All These Leaves

    • says

      Diane, I’ve seen some photos of people tossing Japanese barberry and now they make sense! I’d also prefer to see more resources going into native plants but apparently there’s a good deal of interest in developing sterile cultivars of some well known invasives. It seems to be a sign of the times that we need to accept (but not necessarily embrace) while still advocating for the use of native alternatives to invasive plants, sterile or not.

    • says

      Pat, The lecture did not discuss the relationship between barberry and ticks so I’m not sure if the cultivars will also be the safe haven for ticks that the species seems to be. My sense is that it would have a lot to do with the form of the cultivar. Part of the issue with the pro-tick environment that Japanese barberry tends to create is the humidity levels under the branches that touch the ground. Keeping branches off the ground will certainly impact the humidity level and therefore the number of ticks around the plant. Either way, I always suggest removing Japanese barberry and replacing it with a more regionally appropriate native.
      Debbie recently posted..Wordless Wednesday ~ White Out


  1. […] my last post, I told you about work being done at the University of Connecticut on breeding sterile cultivars of invasive plants.  While some readers were less than enthusiastic about that work, hopefully you’ll be more […]

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