The list of vegetables not to compost is shorter than you'd think. Most vegetable scraps break down fine in a regular compost pile. The exceptions matter for specific cases like worm bins or when dealing with diseased plants from your garden.
You can compost vegetable scraps from almost anything in your kitchen. Carrot tops, potato peels, lettuce leaves, and pepper cores all break down without issues. Even tough items like corn cobs and broccoli stalks work fine. They just take longer than soft scraps.
I learned about the exceptions the hard way with my worm bin. I dumped a pile of onion skins and garlic scraps into the bedding one week. The worms fled to the opposite corner and stayed there for days. They didn't touch those scraps until they had broken down for over two weeks. Now I keep onions in compost piles only.
Alliums like onions, garlic, leeks, and green onions cause problems in worm bins. These vegetables have compounds that repel earthworms. They can harm helpful organisms too. Your outdoor pile handles them fine because the larger ecosystem absorbs the impact. But a contained worm bin can't escape the effects.
Citrus peels present a similar issue for worms. They break down slow and lower your pile's pH as they rot. A traditional pile handles citrus just fine in small amounts. Worm bins struggle with acidic conditions. Keep citrus scraps to less than 10% of what you add to any bin with worms.
My second hard lesson came from diseased tomato plants. I tossed some blight-infected vines into my pile one fall. The next spring, my new tomatoes caught the same disease within weeks. The pile never got hot enough to kill those pathogens. I lost half my crop that year.
Diseased plants top the list of food scraps to avoid composting. Tomatoes with blight, squash with powdery mildew, and peppers with bacterial spot all spread disease. Your pile needs to reach 130-150°F (54-66°C) for several days to kill these pathogens. Most home piles don't get that hot.
Weeds with mature seeds also need caution. Dandelions gone to seed and crabgrass heads can survive your pile. You'll spread them through your garden when you use the finished compost. Pull weeds before they set seed, or send seedy plants to municipal composting where piles get hotter.
Here's a quick rule for your kitchen scraps. If you have a traditional outdoor pile, add almost any vegetable waste you produce. Onions, garlic, and citrus break down fine with time. If you run a worm bin, skip the alliums and go easy on acidic scraps. Your worms will thank you for it.
Don't overthink vegetable scraps in your pile. The vast majority work great as nitrogen-rich greens. Save your worry for actual problem items like meat, dairy, and oils. Those attract pests and create real issues that vegetables never will.
Read the full article: Composting at Home: Complete Guide for Beginners
