The weeks after Halloween bring a disposal challenge for most homeowners, and we’re not just talking about all the leftover candy. The problem: What do you do with your leftover pumpkins? Happily, composting is the perfect solution for disposing of your sagging jack-o-‘lanterns, as well as all the other pumpkins and gourds that graced your hearth and home.
Leftover pumpkins are vegetable wastes, meaning they can supply nitrogen needed by bacteria that decompose organic wastes into finished compost. Leftover pumpkins and other higher-nitrogen “green” composts are mixed in a compost pile with “brown” composts, like shredded leaves, to create the right carbon-nitrogen balance needed for decomposition. That makes pumpkins a good source of nitrogen for the composter during the fall, when green yard wastes may not be as available.
Just tossing your leftover pumpkins into a leaf pile will not create compost anytime soon. The first thing you’ll need to do is to chop those pumpkins up into smaller pieces; pieces less than three inches work best. This creates more surface area to which the decomposing bacteria can attach, and that means faster decomposition in the compost pile or backyard composter.
Use a shovel to chop up the pumpkins nearby where you will compost them. Avoid chopping near anything you don’t want splattered; whole pumpkins are moist inside, and dried pumpkin pulp can be messy. But you can use that mess to your advantage, for chopping up pumpkins is a messy-fun task that may appeal your household’s youngsters or neighbor kids.
Pumpkins chopped up into small chunks are ready to become a layer in the compost pile or composter. Try spreading a one- to three-inch layer of pumpkin waste in between layers of shredded leaves. One of the nice things about composting whole pumpkins is that they already contain moisture; water is needed to create the moist environment preferred by the best bacterial decomposers. But you’ll likely still need to add some water to the pile to keep the moisture level just right for composting.
Even if you don’t have a composter or compost pile set up in your own yard, pumpkin leftovers can still help feed your soil. Gardeners for centuries have buried organic wastes in the garden, and composting by burial can be an earth-friendly way to recycle a few leftover pumpkins. Mix the chopped pumpkins with about an equal part of shredded leaves, buried at least five inches under the soil surface to keep away problem insects and other pests. The time it takes the pumpkin to decompose will vary by how warm the soil is this month and through the winter. In most regions the pumpkin-leaf mix will be unrecognizable by next spring, well on its way to becoming soil humus.
The time it takes pumpkins to decompose in the compost pile will vary, especially in colder regions. Adding chopped up pumpkins to a compost pile that is being regularly turned, and where decomposing bacteria are already established and working, could result in finished compost within two months. Pumpkins added to a pile not regularly turned, like a big pile of shredded leaves, will take longer to decompose and may not be ready to incorporate into the soil until six months or longer.