The Dirt on Soil: Why Microbes Matter
Subterranean Secrets
Every gardener dreams of a thriving, vibrant garden. We spend time choosing the best plants, ensuring they get enough sun, and carefully watering them to ensure the perfect hydration… But what if the true secret to a flourishing garden lies not in what we see above ground, but in the teeming, invisible universe right beneath our feet?
Fertile, natural soil isn’t just plain dirt; it's a living ecosystem packed with billions of microscopic organisms. This complex community is the engine that drives plant health. By understanding and cultivating some of the pieces of the microbiome puzzle, you can transform your garden's health from the ground up.
What Are Microbes?
In the thriving community called the microbiome, there are individual microscopic organisms that work together to support the environment in which they live. These individual organisms are called microbes.
There are five primary types of soil microorganisms:
Bacteria
Actinomycetes
Fungi
Protozoa
Nematodes
While the soil microbiome is incredibly diverse, there are three powerhouse groups that every gardener should know. By harnessing and using this knowledge you can transform your own personal garden right before your eyes.
1. Bacteria: The Master Recyclers- As the most abundant microbes in the soil, bacteria are the ultimate decomposers. Their primary role is to break down organic matter—from last year's fallen leaves to compost—and convert essential nutrients into forms that your plants can easily absorb. Think of them as the chefs of the soil, preparing a nutrient-rich feast for your plant's roots.
2. Fungi: The Great Connectors- There are millions of fungal species, but a particularly vital group for gardeners is Mycorrhizae. These beneficial fungi form a symbiotic relationship with over 90% of all plant species. They create a vast network of fine threads, or hyphae, that extend far beyond the plant's own root system, effectively acting as a root extension. In exchange for sugars the plant produces through photosynthesis, the fungi transport crucial resources such as water and nutrients like phosphorus directly to the plant, dramatically improving its resilience and growth.
3. Nematodes: The Benevolent Predators- The word "nematode" can make some gardeners nervous, but the vast majority of these microscopic worms are allies, not enemies. But don’t worry! These micropredators do not harm people, pets, plants, or earthworms, making them a very useful tool in your garden. Beneficial nematodes are essential regulators of the soil ecosystem. They act as micropredators, grazing on disease-causing organisms and keeping harmful pest populations in check. Furthermore, as they consume other microbes, they excrete nutrients they have gathered right into the root zone—a process called nutrient mineralization.
Putting Microbes To Work
Ready to recruit these microscopic helpers for your own garden? Here are three straightforward and effective ways to introduce beneficial microbes to your soil.
1. Worm Castings - Also known as “vermicast”, is one of the easiest ways to add biology and gentle nutrition to your garden. Worm castings are produced through the digestive process of worms as they eat and excrete organic matter to form a nutrient and beneficial bacteria-rich compost.
You can add worm castings when transplanting by adding directly to the root zone (about 1-2 tsp) or you can top dress (about 1/4 cup for every 6" of growing diameter) and scratch them into the soil of established plants to get the benefits.
2. Mycorrhizae - Mycorrhizal fungi can be added to your soil when you transplant by adding a small amount of a granular version of the fungi to the root zone. There are also water-soluble versions which can be watered into existing plantings, some of which also contain "microbe food" such as molasses to help maintain a strong population.
3. Predator Nematodes - Not to be confused with pest nematodes, predator nematodes consume insects and larvae that live in the soil, even ones as large as cutworms. They work especially well for controlling fleas and fungus gnats. They are added by mixing with water just before applying to your soil. They are also being used experimentally as a foliar spray against leafminers in controlled environments. Who would have thought?!
Let’s Cultivate A Healthier Garden Together
Moving beyond the mindset of simply feeding the plant to actively nurturing the soil is the hallmark of a truly advanced gardener. The health, resilience, and vitality of your garden is directly tied to the life within its soil. By introducing and sustaining populations of beneficial bacteria, fungi, and nematodes, you are no longer just a gardener—you are the cultivator of a thriving, complex ecosystem.
Start with one of these simple methods. You will be rewarded with stronger plants, richer soil, and a deeper connection to the living world working in harmony just beneath the surface.