A common question posed by those new to composting is Can I compost rotten fruits and vegetables? While this seems like a simple question, the answer is quite complicated.
Why? Because it all depends on how you define rotten, and what caused that specific rot in the first place. A bruised apple, a bag of slimy lettuce, or a box of moldy potatoes may all be classified as rotting, but all have unique causes that determine if and how they should be added into a compost pile.
Composting rotting fruits and vegetables: In general, rotten fruits and vegetables are safe to put in a compost pile. However, there are exceptions, so we should be familiar with the signs of an unsafe compost ingredient.
What Is Rot?
The official definition of rot is:
“To undergo decomposition”
If you have ever composted, you know decomposition is the goal. We want our entire pile to rot. So, problem solved. Rotten fruits and vegetables are safe to compost.
And… that’s where the answer gets complicated.
There are many different reasons a plant, fruit, or vegetable may rot:
- Changes in enzymes
- Changes in chemicals
- Microbiological activity
- Macrobiological activity
Most causes of rot are beneficial and harmless in a compost pile. However, there are a few that may spread disease or encourage pests.
Enzymes are the driving force behind photosynthesis and fruit ripening. Once the fruit is picked, enzymes will continue ripening it, and this will eventually lead to it being overripe and inedible.
A fruit is anything that came from a flower, so cucumbers, pumpkins, snap peas, green beans, peppers, and squash all count as a fruit.
Overripe fruit is safe for a compost pile.
Chemicals are responsible for changes in flavor, and browning that is not related to being over ripe. This is mostly due to oxidation, or oxygen interacting with a chemical in the plant material. This can cause different reactions, but none are harmful in a compost pile.
Microbiological activity is where things get interesting. Microbes start breaking down fruits and vegetables once chemical and enzymatic changes have weakened them. (See Thriving Yard’s recommended compost activators that include beneficial microbes for kickstarting a compost pile).
Most are harmless, but there is one to be very cautious of.
If you process and can your own fruits and vegetables, you must be careful to inspect jars for botulism. If there is any sign that your canned foods have botulism, throw the entire container away using gloves. DO NOT compost the contents. Although rare, botulism can survive the composting process, and then grow in anaerobic conditions inside your pile.
Macrobiological activity is one cause of rot that should disqualify plants from the compost pile. This category refers to damage by visible pests, like insects and rodents.
Most damage caused by insects is frustrating, but not dangerous. However, if you’ve harvested food from the garden that has attracted or been damaged by an aggressive pest, it is best to throw it away.
Many damaging insects can survive in infested plant material and become active again when you use your compost. Burn or destroy plants that have infestations to prevent them in the future.
If your fruits and veggies are rotting due to rodent activity, throw them away. If you put these items in a compost pile, they will follow the food and burrow into your pile. It is best to take care of the rodent problem first, and then you can focus on building a new active compost pile.
Can I Compost Moldy Fruits & Vegetables?
Yes. Molds are a microbiological cause of rot, and most molds that occur on fruits and veggies are harmless.
If your garden veggies are molding, it is probably because they were not harvested in time, and cooler weather moved in. This is what happens in nature when seasons change, and it is perfectly safe to throw those moldy tomatoes and apples in the compost pile.
If produce in your fridge has developed mold, then it is almost irrelevant to composting. The mold that grows in a cold, dark, humid environment will not survive the compost pile. The mold will quickly die, and a new mold will take over to help with decomposition.
Can I Compost Brown, Slimy Lettuce?
Probably not. Spoiled lettuce would surely decompose, but the risks associated with it are too high.
Three common foodborne illnesses are found on leafy greens:
These bacteria do not cause rot. Rather, store-bought leafy greens spoil quickly, and these bacteria can survive on the leaves as they are rotting, or in the liquid that collects inside the packaging.
These bacteria are generally not a concern for home gardens, unless you are using manure. Tainted water supplies and improperly-composted manure are to blame for most outbreaks, and due to the short shelf-life of salad greens, many people will have already consumed infected plants before a public notice can be given.
So, odds are you won’t know you have infected lettuce until weeks after you have thrown it into a compost pile. Due to this, and the incredible ability of these bacteria to survive harsh environments, it is best to just throw spoiled salad greens in the trash, and start growing your own.
Can I Compost Rotting Plants?
If your growing season is coming to and end, and the weather has cooled off, you will notice many plants in your garden will begin to die and decay. This is a normal process, and these plants can be thrown in the compost pile as long as there is no active insect population affecting them.
However, if your plants succumb to a disease that causes rot while it should be growing and thriving, these plants need to be pulled and destroyed. Some diseases cause root rot, others cause stem or leaf rot, and others cause the fruit to rot before it’s ripe.
While not all diseases can survive composting (and, in fact, many cannot survive active composting), it is always best to be safe and destroy material that may infect your garden.
Composting is a great way to reuse materials that could be thrown away. In most cases, rotten produce and plant material will be safe in a compost pile. Even diseased material is usually destroyed during active composting.
However, it is always better to be safe and protect your garden and yourself from harmful pathogens.
Why are my bananas rotting so fast?
Bananas produce the hormone ethylene, which is responsible for the ripening of fruit. Many fruits give off small amounts of ethylene, but bananas release so much they’ve been dubbed the “killer fruit.”
If you store bananas in a closed space, like a refrigerator or cabinet, they will spoil very quickly from their own ethylene gas. If you store other produce next to them on the counter, that produce will also spoil quickly. You can use this hormone to your advantage, if you are careful. You can put underripe fruit near bananas in order to speed up the ripening process, but watch it to make sure you use the fruit as it ripens to prevent spoiling.
Why is my compost molding?
Because it’s decomposing! This is a good sign. However, there is one mold you should watch for during the composting process. Although rare, Aspergillus spores can grow in compost piles, and these spores can cause respiratory problems. If you notice respiratory issues after turning your compost pile, you should wear a mask.