It is interesting to think about all the mysterious interactions that happen between plants and the soil. I recently attended a presentation about how mycorrhizal soil inoculates help with establishing prairie plants. Scientists can harvest soil microbes from healthy prairie, grow them in the lab, and then inoculate a future prairie restoration site by drilling the microbes into the soil. Many native plants that are found in a prairie have developed special interactions with fungi and bacteria in the soil. These interactions are beneficial to both parties in a symbiotic relationship. For example, bacteria fixing nitrogen out of the soil to feed the pea plant and the plant providing a special place for the bacteria to live in it’s root nodules. Often these interactions are species specific so that a specific type of plant will only interact with certain fungi or bacteria. It makes sense that the microbes in the soil and the native plants have evolved together over time so that native plants do best with native soil microbes.
In our gardens, most likely many of the native soil microbes are missing from the soil ecosystem. Microbes can be killed by being exposed to sun from tilling, soil compaction from vehicles, the soil horizons being mixed up from construction, and landscaping poisons. Most importantly a healthy garden of native soil microbes requires that the native plants that the microbes depend upon be present. Lawn and invasive species have a different set of soil microbes that can be detrimental to native species. In most cases when we plant a native garden we are not planting into the nurturing soil that the plant would experience in the wild. It is amazing that native plants do as well as they do in our gardens. Some native plants are pickier then others about their preferred soil microbes. It is easier to grow plants that are early successional species, better known as weedy species, like annuals. These early successional species also appear to be the best adapted to have relationships with a broader range of soil microbes that are more tolerant of poor soil conditions. This can explain why it is easier to quickly grow black eyed Susan than New Jersey tea.
Much like planting native plants to attract native insects, we may also be attracting native soil microbes to our yards. It may be that growing easy native plants in the garden now is building a healthy native soil that will create a more welcoming environment for the more difficult to grow natives in the future. Plant diversity, insect diversity, bird diversity, and soil diversity are all building on each other, creating a more diverse and a more truly native garden.
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