Natives vs aliens - the great gardening debate continues

I did a search on this blog recently to see how often I've mentioned native plants. The answer is: A LOT. That, of course, is because native plants are often mentioned as a good choice for environmentally friendly landscapes.

In many cases, the use of native plants is cause for debate, and often, heated debate. Some advocates of native plants think that gardeners should plant ALL natives. Others feel that it’s okay to plant both natives and non-natives, which are sometimes called alien or exotic species.

The debate has been a hot topic on local gardening blogs recently, in part because of a New York Times Op Ed piece entitled Mother Nature’s Melting Pot, in which writer Hugh Raffles expresses his opinion that “non-native animals and plants …provide significant benefits to their new home.”

The debate has been a hot topic on local gardening blogs recently, in part because of a New York Times Op Ed piece entitled Mother Nature’s Melting Pot, in which writer Hugh Raffles expresses his opinion that “non-native animals and plants …provide significant benefits to their new home.”

Raffles goes on to make statements such as  “many of the species we now think of as natives may not be especially well suited to being here” and “non-native plants and animals have transformed the American landscape in unmistakably positive ways.”

The NYT’s piece has been noticed and mentioned on some of my favorite local garden blogs, including Garden Rant: Uprooting the Gardening World and Grounded Design.

I've been reluctant to add my two cents worth to the debate, since I admittedly do not have any formal education on the subject. So instead of an opinion, I thought I would mention some of the key points that keep me, and others, so confused about natives.

First, what is the definition of a native plant?

Native plants are generally defined as those that occurred here without human introduction. In other words, they are the plants that were here when this continent was wild and natural. They sprung up on their own, were dispersed by wind and wildlife, and evolved and were acclimated to the characteristics of the local conditions: the climate, soils, timing of rainfall, drought, and frost; and interactions with the other species inhabiting the local community.

This definition is the basis of why native plants are assumed  good for the environment. Plants which are acclimated to local conditions would logically be more adapted to surviving local conditions and supporting local wildlife.

Now, before I go any further with the discussion of native plants, picture for a moment what this continent looked like before it was “discovered” and “civilized”. In many ways, it was a wild, almost hostile wilderness. Was it beautiful and self-sustaining? Probably. Did it need pesticides and fertilizer and irrigation systems to survive? Of course not. Was it an environment in which the “pioneers” chose to live? No. Immigrants to this country immediately began chopping and thinning and adding and taking away things from the soil and planting new things that they brought from their home countries. The definition of native plants says that they were acclimated to the conditions of the land hundreds of years ago. In my un-trained, un-scientifically educated mind, it doesn't make sense to assume that those same plants would necessarily be acclimated to current site conditions.

My husband and I live on piece of property that is very, very wooded. We only have small  garden areas. So, yes, 95% of our yard consists of the native plants that have been here for hundreds of years. As for all of the other garden areas, when our home was built, huge truck loads of dirt were trucked in to raise the foundation. So whether we leave that dirt and try to plant in it or add supplements, whatever we end up with is NOT native soil. The truth is, not very many of the factors that affected the native landscape “before human intervention” are present in modern landscapes.  The soil is different, not just because it has been moved around  from place to place but also because hundreds of years of man-made "stuff" has seeped into it and trucks and homes have compacted it. The climate is different, the drainage patterns are different.

There is a great resource on Virginia.gov entitled Native Plants for Conservation, Restoration and Landscaping. Many of the points in the document only add to my confusion.

Plants evolve over geologic time in response to physical and biotic processes characteristic of a region: the climate, soils, timing of rainfall, drought, and frost; and interactions with the other species inhabiting the local community. Thus native plants possess certain traits that make them uniquely adapted to local conditions, providing a practical and ecologically valuable alternative for landscaping, conservation and restoration projects, and as livestock forage.

If plants evolve over time in response to the characteristics of the region (which certainly have changed over the last few hundred years), why is it logical to think that only the NATIVE plants have evolved to fit the characteristics of our present-day site conditions?

In North America, plant species are generally described as native if they occurred here prior to European settlement. This distinction is made because of the large-scale changes that have occurred since the arrival of the European settlers. The Europeans imported a variety of plants to this country, many are still the major component of traditional lawns and gardens. They also include many beneficial plants important in farming, such as vegetables and grains. Today, approximately 25% of flowering plants in North America are non-natives or alien species, most of Eurasian origin.

Again, if the European settlers brought plants over here hundred of years ago, wouldn't they now be adapted to current site conditions?

I have never advocated the use of ALL native plants to anyone who doesn't make the choice on their own. First, because I think that gardens should be places of pleasure and creativity.  Gardens are where humans can work hand in hand with nature to create their own, personal work of art, and trying to direct what or how someone plants would stifle their creative process.

But the main reason that I don't "push" native plants is because I believe much more in the theory of "right plant, right place", or choosing plants to fit your CURRENT site conditions, not the conditions of what your part of the continent was like before humans set foot on it. And it makes sense to me that if I choose plants that fit the soil, water and temperature conditions for my site, then they will need less maintenance, less water, less chemicals, and, therefore, will be better for the planet, as it is today.

Again, I'm not an expert on the subject. I learned the lessons of  Right Plant, Right Place from various horticultural classes that I have taken and they have lead to my continued advice to learn to Work With Mother Nature, not against her. I believe that  getting to know your own property is key. Walk around, see where the water settles, get a soil sample, check out where the sunny and shady spots are. I'm pretty sure you will find out that none of that is the same as it was hundreds of years ago.

I certainly understand the value of using some native plants. But the benefit of using plants that
are suited to our current site conditions is that they shouldn't require extra water or fertilizer or pesticides, which will keep us from harming the current environment  even more and maybe, just maybe, will help us get the planet back to the way it was before we started "civilizing " it.

To quote one of my favorite aliens, doing anything else would seem illogical.

Resource for more information on the concept of Right Plant, Right Place:

Landscaping and Gardening – Fairfax County

Soils and Drainage - Fairfax County

Plant Right for Your Site

Waterwise Landscaping and Watering Guide (pdf)