Soil Building Basics 3: Plant Diversity

"Soil is a living thing and needs to be kept covered. If you can see the soil, it is losing carbon, losing vitality, losing life. There is no bare soil in a healthy forest or prairie. The most effective way to regenerate soil is to maintain a living cover of at least 10 different kinds of plants for as much of the year as possible. Plants and their symbiotic microbial partners sequester the carbon that creates and maintains fertile topsoil. Increasing the level of soil carbon improves the health and productivity of farms, gardens and orchards, and helps stabilize local, regional and global climate."

-Christine Jones

Did you know that every plant has a unique relationship with a specific set of microbes underground at its roots? The more species planted, the more diversity is supported underground through these plants. Greater diversity above and below the ground also equals greater resilience.

Did you know that if you can increase the diversity and get microbes levels above a certain threshold, a super-abundant synergy happens in the soil?! Specific beneficial compounds are produced when different microbes reach a certain threshold. This boosts production and plant health to higher levels than if only a single species is grown. It's simple amazing. This synergistic effect which is just now being measured by science is completely counter to a common belief that extra plants "steal" nutrients from each other. Reintroducing variety and diversity can jumpstart these microbial systems underground into higher levels of abundance that support greater production and quality of plants aboveground. Our understanding of the way microbes work together is so new, and gets more and more inspiring as the science catches up to explain why these incredible effects happen. For example, it helps us understand why more plants vying for a "slice of the pie" so to speak, can actually produce MORE PIE?!? Just by participating, more plants increase the abundance in the soil so that it supports yet more life. There are other win-win, just-grow-more-pie scenarios in nature, too, like with bees. Just the very act of participating in harvesting pollen creates bigger fruit set, bigger and more genetically diverse seeds, more flowers from those seeds and more pollen for the following next season. The more they take, the more they grow.

Each plant has a different type of root shape: depth, width, density and growth pattern. Everywhere the roots reach, there is a interaction going on between the plant and the soil ecosystems around them. By planting a diversity of root shapes, there is an impact on the soil and soil building processes at multiple levels underground. Imagine the plants on the surface like the tips of glaciers with a small portion visible above that can sometimes indicate a huge mass below under the water line (in this case the soil line!). Plant with that view in mind.

One way to add resilience to a backyard is to diversify and revitalize the lawn from just one species to many. The predominant grass type in most lawns here in the US is Kentucky Bluegrass (Poa pratensis). Despite the name, it is actually not from Kentucky but introduced to North America from Europe and North Asia. It has relatively shallow roots, likes moist and cool conditions, and fertile, well-drained soils. As a cool season grass, it needs a lot of water and fertilizer to keep it green especially in the hot and sometimes dry summer months in North America.

However, many native and beautiful alternatives exist that can enhance the resilience of the landscape. Warm-season and/or native grasses can better withstand the heat of summer, resist drought, mitigate flooding and also are hosts for specific caterpillars like several endangered Skipper butterflies. Buffalo grass (Bouteloua dactyloides) and Pennsylvania Sedge (Carex pensylvanica) are two excellent of many!

And while we're at it, why not reincorporate other broad-leafed plants into the lawn? Prairie clover (Dalea purpurea) and heal-all (Prunella vulgaris) can be trampled or mowed just like many grasses and they also support many species of endangered bumblebees and other insects. Clover can fix nitrogen and was actually originally in lawn mixes in the US for this reason.

You might even consider adding a warm-season, clumping grass (that doesn't spread) along a border of a yard or lawn for added texture or as an accent. These gorgeous grass varieties don't spread and don't need to be mowed. They maintain color throughout the year with warm browns, golden yellows, soft greens, hints of blue, reds or even purples. The seed heads produce unique shapes and lines that support texture and interest in a meadow aesthetically especially paired with wildflowers (if you just decide you want a full meadow!) throughout the season as well as an important food source for wildlife like bobolinks and migrating birds. Many native grasses are important food sources or host plants for endangered butterflies and ground-nesting bees. They anchor the soil and feed the soil biology deep down in the ground. Some produce seeds that can be used as a wild grain to make nutrient-rich flowers. They have names like side oats grama, purple lovegrass, little bluestem, and sweetgrass.

There are so many options for incorporating resilience by planting diversity. Backyard "cocktail cover crops" offer a unique way to do it in the vegetable garden as well as in a lawn. Another post for that topic soon!

Increasing resilience can happen quietly all around us even in the grass beneath out feet. There is a vast, teeming and beautiful diversity that is possible below the ground if we support it with diverse plantings above ground!

For more information:

Graime Sait's article on the amazing effects of plant synergy specifically with the idea of "cocktail cover crops": https://blog.nutri-tech.com.au/cocktail-cover-crops/

Sedges as Lawn Alternatives: https://hoffmannursery.com/blog/article/sedges-for-lawn-alternatives

Buffalo grass as a lawn alternative: https://hoffmannursery.com/blog/article/try-a-different-lawn-with-buffalo-grass

Prairie Moon's nursery's "Eco Grass" - blend of slow growing, deep-rooted grasses: https://www.prairiemoon.com/eco-grass