Watermelon rinds, a common byproduct of enjoying the refreshing summer fruit, are completely compostable and represent a valuable resource for your garden. Composting the rinds enriches your soil with beneficial nutrients, preventing this material from contributing to methane production in landfills. The rinds function as a nitrogen-rich “green” material, providing nitrogen, phosphorus, and potassium that fuels the microorganisms responsible for decomposition.
Essential Preparation Steps for Rind
The density and size of a watermelon rind require preparation before being added to a compost pile to ensure efficient decomposition. Cutting the rinds into smaller pieces, ideally 1-inch squares or smaller, significantly increases the surface area that microbes can access. This physical breakdown expedites the decomposition process, preventing large chunks from taking months to fully break down.
While the tough rind is compostable, scrape off any large amounts of residual pink flesh before composting. Minimizing the sticky, sweet flesh reduces the immediate attraction for common pests like fruit flies. Removing non-biodegradable stickers or labels is also necessary to prevent plastic contamination in your finished compost.
Managing Moisture and Decomposition Rate
Watermelon rinds are composed of over 90% water, making them a very wet, nitrogen-rich “green” material that can easily disrupt the moisture balance of a compost pile. This high moisture content requires immediate balancing with dry, carbon-rich “brown” materials to maintain the ideal moisture range of 40 to 60 percent. Failure to compensate for the excess liquid can lead to a soggy pile where airflow is blocked, encouraging anaerobic decomposition and foul odors.
To counteract this, incorporate a generous amount of materials like shredded newspaper, dry leaves, straw, or sawdust directly alongside the rinds. These brown materials absorb the excess moisture and provide the necessary carbon to achieve the optimal carbon-to-nitrogen ratio, which is typically around 30:1 for rapid breakdown. Following the addition of the rinds and browns, turning the pile mixes the materials and introduces oxygen, which helps the microbial community break down the tough rind fiber more quickly.
Avoiding Common Composting Issues
The combination of high moisture and residual sugars in watermelon rinds can present challenges in the form of pests and unpleasant smells if not handled correctly. The sweetness of the fruit scraps is particularly attractive to common pests, including fruit flies and rodents. To mitigate this issue, the prepared rinds must be completely buried deep within the center of the compost pile, away from the surface.
Burying the rinds in the pile’s hot core, often a foot or more down, helps ensure they are quickly covered and begin to decompose before pests can locate them. Immediately covering the newly added scraps with a thick layer of finished compost or dry brown material further acts as a barrier, deterring scavengers and flies. If the pile begins to emit a strong, rotten odor, it indicates the compost is too wet and lacks sufficient oxygen; adding more dry brown material and turning the pile quickly restores the necessary aerobic conditions.