What Is Humus And How To Increase It In Garden Soil

Every thriving garden starts with a secret ingredient underfoot: humus. Scientists have long sought to understand humus, as shown by trailblazing forest soils researcher S.A. Wilde's musings in 1971 (via Horizon Documentation), "Humus: What is it? The spirit of the soil. The product and the source of life." Humus originally meant "soil" in Latin, but its meaning has evolved over the years to refer to a specific component: the stable part of the soil that helps it hold water and nutrients. Nature's way of revitalizing soil, humus forms from decaying organic matter — plants, animals, and insects breaking down with the help of bacteria and fungi. This natural process creates a soft, spongy material rich in nutrients like nitrogen, phosphorus, magnesium, and calcium, all essential for plant growth. Earthworms and rain further distribute humus through the top layers of soil, transforming it into fertile, nutrient-dense topsoil that every garden needs for healthy plant growth.

Humus works by making the soil looser and better at absorbing water and circulating air. This helps plants draw up those necessary components of life through their roots. Furthermore, its presence encourages a thriving population of beneficial microorganisms, which support plant health and decrease the prevalence of diseases. Whether in natural ecosystems or cultivated gardens, humus is a cornerstone of fertile, productive soil.

While forest soil naturally produces humus, your yard is no forest floor. In residential neighborhoods, leaves get raked up, dead animals aren't left to rot, and humus doesn't always naturally balance the soil. If you're wondering whether you have enough humus, your soil pH can give you a hint. It should range between 6 and 7 — a balance humus naturally helps maintain — so essential nutrients remain available to plants. If you want to learn more, here's how to create DIY tests to check the health of your soil.

If your garden needs more humus, the best way to boost its levels is to add soil conditioners to your garden. Consider starting a traditional compost pile or a vermicompost pile. With the latter, you use earthworms to break down organic material, such as kitchen scraps, yard waste, and leaves. Once these are fully decomposed, you'll be left with a rich humus to add to your garden. 

Composting at home has a lot of benefits. However, if you don't have time of space, you can purchase organic material to add to your soil, such as composted Hoffman Organic Cow Manure or Back to the Roots Organic Worm Castings. You can also consider adding organic mulch, such as shredded leaves, straw, or wood chips, which will break down into humus over time. Simply use a rake to spread the humus over the growing medium a few weeks before planting, and nature will help distribute it through the topsoil.