Tomatoes can be composted, but they require specific management to ensure a balanced decomposition process. Tomatoes, including the fruit and healthy plant matter, are excellent additions to a compost pile because they provide a rich source of nitrogen and moisture. However, the high water content and potential for disease and seed survival mean they should not simply be tossed onto the pile without preparation. By understanding how to balance the fruit, neutralize the seeds, and handle the vines, you can safely recycle this common garden and kitchen scrap into beneficial soil amendment.
Composting Tomato Fruit and Balancing the Pile
Fresh tomato fruit is classified as a “green” material, meaning it is high in nitrogen and moisture. This nitrogen is necessary to feed the microorganisms responsible for breaking down the organic matter in the pile. However, the high water content of the fruit can quickly saturate the compost, leading to conditions that exclude oxygen.
An overly wet pile becomes anaerobic, which slows decomposition and often results in foul odors. To prevent this soggy environment, balance the tomato fruit with “brown” materials, which are rich in carbon and help absorb excess moisture. Ideal carbon sources include dried leaves, shredded newspaper, straw, or sawdust.
It is helpful to chop or crush the tomato fruit before adding it, as smaller pieces decompose much more quickly. For every layer of wet tomato scraps, a generous layer of dry brown material should be added to maintain a balanced carbon-to-nitrogen ratio. Burying the fruit scraps deep within the pile and covering them completely also helps to deter pests and speed up the decomposition process.
Neutralizing Tomato Seeds and Preventing Volunteer Plants
One common issue when composting tomatoes is the survival of their seeds, which can later sprout into unwanted “volunteer” plants when the finished compost is spread in the garden. Tomato seeds are notably hardy and can easily survive the cool temperatures of a slow, or “cold,” composting system. To guarantee the seeds are killed, a process known as thermal inactivation must occur through “hot” composting.
This process requires the compost pile to reach and maintain a temperature of at least 131°F (55°C) for a minimum of three consecutive days. Higher temperatures, such as 140°F (60°C), can ensure a more rapid and complete kill of the seeds. Achieving these temperatures requires a sufficiently large pile, often measuring at least three feet by three feet by three feet, to generate and retain heat.
Regularly turning the pile is necessary to aerate the material and move the cooler outer layers into the hot core. This sustained heat cycle effectively destroys the viability of the seeds, preventing them from germinating. If you cannot maintain these temperatures, it is safer to dispose of the seeds through municipal composting or simply accept the task of pulling the resulting volunteer seedlings.
Guidelines for Composting Tomato Vines and Diseased Material
The non-fruit parts of the tomato plant, including the vines, stems, leaves, and roots, can be safely composted only if they are completely healthy. Tomatoes are susceptible to several common and persistent plant diseases, such as Fusarium wilt, Verticillium wilt, and various blights. The fungal spores or bacteria that cause these issues can often survive the lower temperatures typical of many home compost piles.
If any part of the tomato plant shows signs of disease, it should be excluded from the home composting system. If these pathogens survive the process, the finished compost will act as a vector, spreading the disease to new plants and garden areas when applied.
For any diseased tomato material, the safest disposal method is to bag it and send it out with the household trash. Commercial operations can reach the sustained high temperatures needed to destroy plant pathogens, which are often difficult to achieve in a backyard setting. Avoiding the composting of diseased material helps to protect the health of your future garden.