A small but growing number of local governments are now mandating that landscapes in their jurisdiction use only “native” plants. (See this recent article in the Philadelphia Inquirer.)
Further, environmental groups such as the Audubon Society now are promoting the implementation of model native plant ordinances by local governments.
What’s behind this movement? Are these ordinances a good idea? What are the implications for the landscape contracting industry? Let’s take a look.
Growth of the native plant movement
Those advocating the use of native plants in the landscape have been growing over the past decade. Once confined to a small segment of the public (native plant enthusiasts, some governmental organizations, environmental groups and niche nurseries), native plant advocates have now gone mainstream. The number of nurseries specializing in native plants has grown and it’s common to find entire sections of garden centers now devoted to their native plant offerings.
So why the increased interest in native plants? The short answer is the science supports it. Much research has been done over the past 20 years showing that indigenous plants play an integral role in supporting biological diversity in their areas.
What gave the native plant movement its push into the mainstream was a book by a University of Delaware entomologist Doug Tallamy, Ph.d., Bringing Nature Home: How Native Plants Sustain Wildlife in Our Gardens. Tallamy’s book summarizes the scientific research about how the terrestrial animal kingdom is connected to the plants with which they’ve co-evolved.
The brilliance of Tallamy’s work is that he wrote the book not for the scientific community, but for the homeowner/gardener. Any given weekend will find Tallamy speaking to a garden club or meeting of master gardeners about his findings. So all of this scientific research, which had been bound up into academic journals like the Journal of the Lepidopterists’ Society, are now readily available to the general public in a very readable book.
Tallamy is a butterfly and moth expert. He found many species of butterflies and moths were dependent on very specific plants for food. For example, the monarch butterfly depends exclusively on native milkweed. No milkweed, no monarchs. Other species of insects have similar preferences for specific native plant species.
Moving up the food chain, birds depend heavily on insect populations, especially when they’re hatching and raising young; hence, the Audubon Society’s interest in native plants and Tallamy’s work.
Are these ordinances a good idea?
On the other side of the coin, despite Tallamy’s research, some of the benefits of native plants have been oversold by well-meaning governmental agencies and environmental groups. Often brochures from these groups will tout native plants as “carefree,” “low-maintenance” or “drought tolerant.” The implication is that simply because a plant is labeled as “native” you can plant it and forget it.
Nothing could be further from the truth. For example, I know several so-called native drought tolerant species whose response to drought is to die back to conserve moisture in their root systems. They look nice when there’s adequate moisture but disappear when conditions get dry. Is that a good landscape plant?
In fact, native plants are a diverse group in any given area, with a wide range of cultural and climate requirements. A native species that evolved in a shady flood plain near a stream probably won’t do well if planted on a rocky outcrop on a southern-facing slope of the adjacent mountain. Like any plant, native or not, it’s all about the right plant for the right place.
Another factor not taken into account by native plant advocates is that much of the urbanized and agricultural areas of this country have changed dramatically from the environment in which native plants evolved. For example, Pennsylvania was covered by a mature coniferous forest, with 150 foot white pine and hemlocks when the area was settled by Europeans. By the early part of the 1900s, most of Pennsylvania had been clear-cut, leaving a much different environment. The native plant communities that you would have found in the perpetual twilight of a mature coniferous forest would not do well in a typical suburban front yard or the median strip at the local mall.
The bottom line is native plants are not the solution to every horticultural problem you may encounter. As with any plant, they require attention to matching the requirements of the plant with the conditions on the site.
Writing an ordinance that mandates the use of native plants is challenging, to say the least. At some point, writing the ordinance gets down to developing a list of native plants.
Developing a list of native plants can be a daunting project and the cause for much discussion and argument, even among very knowledgeable people. Native to what area? Native to that municipality, that state or that ecosystem? How do you account for the change in the natural environment due to development?
At the extreme is a group of activists in Philadelphia who are insisting that the only trees that should be planted in the city are those whose seeds and provenance can be traced back to the earliest days of the city. My view is that any tree planted in Philadelphia as an improvement!
Implementing the ordinance leads to the enforcement question. Whoever enforces the ordinance will need a high degree of plant identification expertise. Most municipal governments are dealing with budget challenges these days. Where will they get the plant expertise to enforce an ordinance?
How should the landscape industry respond?
First, we should recognize there is good science behind the native plant movement. Read Tallamy’s book. There are good reasons for you to incorporate native plants into your landscape designs and plans. If we ignore the science, we will seem like a clueless interest group simply looking out for our economic interests. We should be seen as the plant experts in our communities.
Second, if you find that a municipal government in your area is contemplating a native plant ordinance, you need to get involved. Contact the local officials and ask to speak to them. Offer your expertise as a horticultural professional. Many times these ordinances are driven by well-meaning environmental activists. The local officials will welcome the expertise of someone who actually works in the field.
Ask the local officials how they intend to enforce the ordinance, where they’ll draw their horticultural expertise, how they’ll develop the list of allowable plants, etc. In many cases, these questions and their complexity will not have occurred to them. I’ve talked to several municipal officials who were contemplating such an ordinance and it took only one meeting where I raised these questions for them to table the ordinance.
Third, suggest a public education program as a better and less expensive way for them to address the benefits of native plants in the landscape. Offer to be a resource to the development of that program. Who knows, it just may lead to some great marketing opportunities and new business.
