Gong, Going, Gone — What Is Happening in My Native Plant Garden?
June 5, 2014
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Scientists recognize that native plants tend to occur in communities where species with similar limits tend to grow together, and these communities are defined by the dominant plant species in them. It is also recognized that the there is a predictable and natural succession over time where one plant community gradually or rapidly replaces another, although there are differing theories of how this complex process of succession occurs. Understanding the structure and functioning of native plant communities is the focus of many scientific studies that go beyond the understanding of most of us native plant gardeners.
However, after watching all the significant changes that occur in my native plant gardens, I can’t help but draw some parallels. It seems to me that in a sense my gardens are mini-communities that are going through their own process of succession. I have two plots where the changes have been dramatic over a 4-5 year period. In one 40’ by 35’ area, I have gone from a planting dominated by Purple Coneflower, Pale Purple Coneflower, and various Penstemons to one dominated by Big Bluestem grass with the original species either gone or only a handful remaining. In another, 50’ by 40’ area, I have gone from an area with sweeping stands of Golden Alexanders to one dominated by Slender Mountain Mint with only a few scattered Golden Alexanders remaining. Sometimes I hate to see the change and really miss my original mix of species.
All of this has gotten me to wondering how these changes happen and what drives the process in my own yard. Even if what I am witnessing is not true community succession as scientists define it, it is some form of succession. Plus knowing that succession will occur suggests some important basics that a person can take into account when doing a native plant garden. First is to just recognize that there is going to be lots of change. The characteristics of the planting site – soil, moisture and light levels—will influence the changes over time. Having an initial seed mix with too large a percentage of seeds of an aggressive species can eventually put that species in control of your garden. A seed mix that has a small number of aggressive species will likely lead to a planting heavily dominated by just a few species.
It isn’t always just which plants are aggressive. I talked to a staff person at one of the large native plant nurseries about what influences succession in our native plant gardens. He described a garden at their nursery site that had lots of Early Sunflower, a plant that I know from personal experience to be very aggressive. He said that one spring, they were suddenly gone and no one knew what had caused the change.
One of the most important factors affecting succession is the total number of plant species in the original seed mix. That seed mix forms the seed bank from which my mini-community will draw as the years progress. Use as large a number of species in the original mix as you can. A large number makes for more plant diversity and less chance that one or two species will take control and crowd out others. It should also make the succession process more dynamic and a little closer to what occurs in nature.
Disappointments aside, it is fascinating to watch all the changes occur and part of the fun of native plant gardening.