Yes, you can add rotten potatoes in compost as long as you cut them into small pieces first. Whole potatoes have a bad habit of surviving the composting process and sprouting in your garden beds later. Chop them up and they'll break down just fine alongside your other kitchen scraps.
I learned this the hard way a few years back. I tossed a bag of soft, mushy potatoes into my compost bin without cutting them. Two months later I spread that finished compost on a raised bed. Within a week I had potato plants popping up everywhere across the bed. They grew right between my lettuce rows and choked out the seedlings I had planted. That mess taught me to always prep my potatoes before composting.
The reason potatoes survive is their eyes. Those small bumps on the surface contain growth buds that stay alive even when the rest of the potato rots away. Your compost needs to hold steady temps above 130°F (54°C) for several days in a row to kill those buds. Piles that run cooler or have cold spots near the edges leave plenty of eyes intact. A potatoes sprouting compost pile is one of the most common surprises for new composters.
The key to composting potatoes safely comes down to prep work. Cut every rotten potato into chunks smaller than 1 inch (2.5 cm). This exposes the flesh to heat and microbes on all sides. Bury the pieces in the center of your tumbler or pile where temps run highest. Mix them with a good amount of carbon-rich browns like shredded cardboard or dry leaves to balance the moisture.
Don't add potatoes that show signs of disease. Blight is the big one to watch for. If your potatoes have dark, mushy spots with a foul smell or white fuzzy mold on the surface, those spores can survive composting. Blight spores spread fast and will infect your tomato and potato plants next season when you use that compost on your beds.
If you spot sprouts coming up in your pile, don't panic. Just turn them back under the material before they grow roots and leaves. The heat in the center of the pile will kill them off within a few days. If a sprout has already grown several inches tall with green leaves, pull it out and toss it in the trash instead. At that point the root system is too strong to break down fast.
Your tumbler makes composting potatoes easier than an open pile does. The sealed drum holds heat better and the regular spinning mixes your potato pieces through the hot zone over and over. You get more even breakdown with fewer cold spots where eyes might survive. Fill to three-quarters full and spin every few days for best results.
Sweet potatoes follow the same rules. They sprout even easier than regular potatoes because their eyes are harder to spot. Cut them small and bury them deep in the hot center of your pile. I once found sweet potato vines growing three feet long through a pile I had ignored for a month. Those things grow fast when you give them warm, moist conditions.
A handful of chopped rotten potatoes adds good moisture and nutrients to your compost batch. They're rich in potassium and break down into dark, crumbly material. Just take two minutes to chop them up before tossing them in. That tiny bit of prep saves you from pulling surprise potato plants out of your garden beds all summer long. Your finished compost will come out clean, rich, and ready to feed whatever you plant next.
Read the full article: Compost Tumbler Guide for Beginners
