Nurturing and supporting healthy soil is the cornerstone of organic horticulture, and at the heart of it lies a vibrant community of soil microbes. These microscopic organisms, including bacteria, fungi, protozoa, and nematodes, play a pivotal role in maintaining soil fertility and supporting plant growth. Without them, soil would be little more than lifeless dirt. This environment that soil microbes exist in is called a “microbiome”. Think of it like a tiny universe existing within healthy soil, consisting of a variety of different organisms working together to create living soil that plants, insects, and other larger animals can’t thrive without.
Soil microbes are best known for acting as nature’s recycling team, breaking down organic matter like dead leaves, plant residues, and animal waste into essential nutrients that plants can easily absorb through their roots. But microbes also play an essential role in assisting plants in taking in those nutrients. For example, Mycorrhizal fungi form intricate networks with plant roots, significantly expanding their surface area for water and nutrient absorption, helping to create a safety net against drought and malnutrition. Nitrogen-fixing bacteria also work with the roots of certain plants to transform or “fix” nitrogen from the air into forms that they can use, a nutrient critical for strong, green growth. These symbiotic relationships not only feed plants but also protect them from stress such as drought, extreme heat, or nutrient deficiencies. Soil microbes also provide food to organisms larger than them such as insects - helping foster the local interconnected food web from the ground up.
Microbes also contribute to soil structure, which is vital for root development. As they consume organic material, microbes produce compounds that bind soil particles together, creating a crumbly, uniform texture. This crumbly structure allows air and water to move freely, providing an optimal environment for plants to grow in. At the same time, beneficial microbes compete with harmful pathogens and pests, preventing fungal issues and diseases like root rot. In essence, a thriving microbial community helps creates a balanced, self-sustaining ecosystem that fosters healthy plants and resilient soil.
So how can I help strengthen the soil in my garden?
To ensure these vital microbes flourish, gardeners can adopt a range of practices to enrich the soil and create a supportive environment:
Incorporate Organic Matter: Regularly add compost, well-rotted manure, or leaf mold (decomposed leaves) to your soil. These materials provide a buffet of nutrients for a wide variety of microbes while improving soil texture. As they biodegrade naturally, different soil organisms will feed and interact at different points of their decomposition. All of these organic materials also add bulk material to the soil - meaning you don’t have to buy bags of soil for your garden!
Apply Mulch: A layer of organic mulch, such as straw, wood chips, or shredded leaves, offers numerous benefits. It conserves soil moisture, keeps the temperature stable, and, as it breaks down, provides a continuous food source for soil microbes. Mulch also acts as a shield, protecting the microbial community from extreme weather conditions like intense heat or heavy rains. Avoid using inorganic mulches such as rubber, pebbles and gravel — these can alter moisture absorption and retention in soil, as well as increase heat. Substances like rubber can also release harmful plastics and “forever chemicals” in your soil, which soil microbes and plants themselves have trouble processing. If you’re growing food crops, it is especially important to use a natural mulch.
Introduce Plant Probiotics: Products like compost teas or microbial inoculants can jumpstart microbial activity in your soil. Compost tea, made by steeping compost in water, can be made at home and creates a liquid containing beneficial microbes that can be applied to your soil. We have also created our own microbial inoculant, our Essential Plant Probiotic, which contains a more targeted variety of beneficial microbes and added plant nutrients for stronger and more uniform results. Applying either of these (or both) to your soil boosts microbial diversity and activity, enhancing nutrient uptake and overall plant resilience.
Avoid Synthetic Chemical Inputs: Many chemical fertilizers (such as common blue powdered fertilizer) and synthetic pesticides are harmful to soil life, disrupting and depleting microbial populations, thus reducing their efficiency and populations. Switching to organic alternatives ensures microbes thrive and keeps the soil ecosystem balanced. For instance, fish emulsion, kelp extract, or organic blood and bone meal are organic fertilizers that provide plants with essential nutrients without harming microbes. They help feed the microbes and the plants! There are also natural pesticides and pest control solutions available for pest and pathogen outbreaks which will not harm the plants or soil life.
Minimize Soil Disturbance: Excessive digging or tilling breaks up the delicate networks of fungal hyphae (underground “root” networks) and disrupts the habitat of beneficial organisms. Soil microbial life is stratified into layers, kind of like a layer cake, and digging too deep too often can disturb these layers. Adopting no-dig or reduced-tillage methods protects the soil structure, allowing microbes to maintain their natural systems where everyone works on their own “floor of the office”. Avoid unnecessary cultivation of soil by controlling weeds by hand, or with an organic herbicide (such a horticultural vinegar).
Use Native Plants: Native plants are ideally suited to your local region and play a critical role in strengthening the overall ecology of your garden. These plants are adapted to thrive in your region’s climate and soil conditions without requiring excessive inputs, care, or fuss. They also attract and sustain beneficial pollinating insects, as well as birds and other wildlife, creating a harmonious and self-sustaining ecosystem that will in turn help benefit the microbes. Native plants serve as both a foundation for healthy soil and a support system for biodiversity, making them an essential component of a beautiful and vibrant garden. Native plants are primed to support and promote local organisms in a way that non-native plants aren’t, with certain native plants benefiting particular organisms (microbes, insects, birds, etc.) especially in a mutualistic partnership where they support each other.
Reduce Annual Bedding Plants: While annual bedding plants are colourful and eye-catching, they are very resource-intensive, requiring significant amounts of water, fertilizer, and care to thrive. Annuals use a lot of nutrients and water to maintain large, colourful blooms throughout the growing season. This is because they are often native to much warmer environments with more significant amounts of rainfall, such as a tropical or subtropical biomes where they would thrive naturally. Moreover, most annuals offer an insignificant benefit to pollinators, birds, and other wildlife because they are bred for temporary aesthetic appeal rather than ecological value. While they may produce a little pollen or seed to feed local butterflies and birds, they will not help to truly build a population compared to a native perennial that returns as a larger plant each following spring. Our native plants have evolved to create an abundance of seed and pollen which our local animals have evolved to search out and eat, and most annuals cannot come close to serving this ecological function. The yearly planting and digging up of annuals is also disruptive to soil layers, preventing the long-term population development of microbial life. Consider reducing your use of annual bedding plants and instead focus on native self-seeding annuals, perennials or flowering shrubs. These alternatives are more sustainable, require fewer nutritional inputs, and contribute to a healthier ecosystem by directly supporting pollinators and other beneficial species. By reserving annuals for small accent areas, you can strike a balance between aesthetics and ecological responsibility.
A garden with rich, living soil becomes a hub for local wildlife. Healthy plants attract pollinators like bees and butterflies, which in turn support bird populations and other beneficial creatures. By creating a balanced, microbe-rich environment, your garden plays a more active role in enhancing biodiversity and fostering a thriving local ecosystem. You will have a more exciting garden that’s truly alive year-round — allowing you to spot travelling insects such as bees and butterflies, and enjoy bird watching year round!
By embracing any or all of these techniques, you can cultivate healthy, living soil that not only supports vibrant plants but also contributes to a balanced, sustainable environment. Thriving soil microbes are the foundation of your garden, ensuring plants are well-fed, more resistant to disease and pests, and better able to withstand drought and other environmental challenges.