Using human or animal hair as a garden amendment is a sustainable practice gaining interest among gardeners seeking to repurpose waste into a resource. This organic material holds potential as a long-term soil conditioner and nutrient source for various plants. The viability of this waste product depends heavily on its chemical structure and how it is applied. Understanding hair’s slow breakdown rate reveals its role as a specialized gardening tool.
Keratin and the Primary Nutrient Content
Hair’s value as a soil amendment stems from its primary building block, a tough structural protein called keratin. Keratin makes up about 80% of hair’s composition. This protein is particularly rich in nitrogen, containing approximately 15% nitrogen by weight—a significantly higher percentage than many common organic fertilizers. Nitrogen is essential for vegetative growth, forming chlorophyll and amino acids.
The fibrous structure of keratin also contains a substantial amount of sulfur, typically around 5%, due to the sulfur-containing amino acid cystine. These strong disulfide bonds give hair its remarkable strength and resistance to degradation. Hair also contains trace amounts of phosphorus, potassium, calcium, and magnesium, which contribute to overall soil health upon release.
Methods for Utilizing Hair in Gardening
Gardeners can incorporate hair into the soil using several methods tailored to its unique properties.
One method is direct soil incorporation, which involves scattering chopped hair across a planting bed and working it into the top few inches of soil before planting. This technique is effective when establishing new beds or containers, where a small handful of hair can be layered at the bottom of a pot to act as a long-term nutrient reservoir.
A second, more common approach is integrating hair into a compost pile. Because hair can clump, it should be distributed in thin layers and mixed thoroughly with carbon-rich brown materials like dried leaves or straw. Chopping the hair into smaller pieces, ideally one to three inches, accelerates the breakdown process by increasing the surface area available to decomposer organisms.
Finally, hair can be used in compressed forms, such as commercially available mats or pellets. These manufactured forms create a slow-release fertilizer that is easier to handle and apply. Alternatively, a thin layer of hair scattered around plant bases acts as a moisture retainer and a natural deterrent for pests like deer and slugs.
Practical Drawbacks and Decomposition Rate
The most significant limitation of using hair as a fertilizer is the extremely slow rate at which its nutrients become available to plants. The highly cross-linked structure of keratin resists microbial breakdown, meaning it can take anywhere from six months to two years to fully decompose. This makes hair a long-term soil amendment, not a solution for immediate nutrient deficiencies.
Adding hair in large clumps can lead to matting, which is detrimental to soil health. These dense, water-repellent mats restrict air and water flow, suffocating plant roots and inhibiting proper drainage. It is important to shred or chop hair and mix it well with other materials to avoid this physical barrier.
Aesthetic concerns are another drawback, as visible strands of hair on the soil surface are unappealing to many gardeners. More importantly, hair treated with chemical products like dyes, bleaches, or strong shampoos may introduce unwanted synthetic compounds into the garden. For this reason, clean, untreated hair is recommended, especially when growing edible crops, to prevent potential contamination.