Composting is one of my favorite ways to transform kitchen scraps and yard debris into gold for the garden—I mean, nutrient-rich humus that fuels next season’s blooms! But it’s such a bummer when you realize halfway through a pile that you’ve tossed in something that will either attract rodents or introduce pathogens to your prized tomatoes (Solanum lycopersicum, native to western South America). Over the years, I’ve learned (sometimes the hard way) which items break down beautifully and which should head to the trash instead. Whether you’re new to composting or you’d like a refresher before summer’s yard cleanup, these thirteen tips will clarify what you can safely add, what to avoid, and how to protect beneficial compost dwellers like earthworms and predatory beetles that help keep the pile healthy.
In this article, we’ll cover everything from kitchen scraps to invasive weeds, meat and dairy, paper products, yard waste, and more—each with practical advice and insights into how various pests and beneficial critters interact with different compost materials. I know how frustrating it is to see fruit flies swarm your bin or to find that sneaky bindweed (Convolvulus arvensis, native to Europe and Asia) has sent rhizomes back from the dead. By understanding what can nourish your compost and what will sabotage it, you’ll maintain a balanced, productive pile that yields rich soil amendment—and maybe even support nesting ground beetles or beneficial nematodes along the way!
Avoid Meat, Fish, and Dairy Scraps
It’s tempting to toss leftover chicken bones or those tiny fish scraps into the bin, but meat, fish, and dairy products can wreak havoc on your compost. These high-protein materials decompose slowly, generating strong odors that attract rodents, raccoons, and opportunistic flies. I once learned the hard way when I threw a handful of shredded cheese into my compost—within days, a skunk family moved in, rummaging through the bin at night! Even if your compost tumbler is secure, the lingering smell permeates the surrounding air, and ants or cockroaches may come calling as well.
Instead, keep your compost smelling fresh by limiting kitchen contributions to vegetable and fruit scraps, coffee grounds, and eggshells (more on those later). If you really want to break down meat or dairy on-site without pests, consider using a specialized hot composter that reaches over 130°F to kill pathogens and denature proteins, but remember those units still require vigilant monitoring. For most of us using backyard bins or tumblers, simply disposing of leftover meat and cheese in the municipal green cart (if accepted) or trash is the safest bet. Your rabbits and worms will thank you for avoiding these smelly ingredients!
Shred or Tear Paper and Cardboard Products
Paper and cardboard are excellent “brown” ingredients—rich in carbon and perfect for balancing out “green” nitrogen sources. But large sheets of cardboard or thick paper take ages to break down if placed whole in your bin. One of the tricks I love is shredding junk mail, tearing egg cartons, and cutting corrugated cardboard into inch-wide strips before tossing them in. The smaller surface area invites fungi and bacteria to colonize faster, which then encourages earthworms to nestle in, chomping away and turning that paper into crumbly humus.
Beware of glossy magazines or paper coated with plastic or heavy inks—they resist decomposition and can leach harmful chemicals. I once added several glossy flyers without thinking, and weeks later, that corner of my bin stayed paper-white and water-resistant. If you’re unsure whether a paper item includes a plastic or wax coating, do the “tear test”: if the edge peels off in a waxy layer or feels slippery, skip it. Standard office paper, brown bags, newspaper (black ink only), and plain cardboard are your friends—just shred them, layer them with moist greens, and watch beneficial mites and springtails spring into action!
Include Coffee Grounds and Tea Leaves
One of my favorite additions to any compost pile is spent coffee grounds—they’re an all-star source of nitrogen and help create a loose, aerated structure that earthworms adore. I save my morning coffee grounds in a small bucket in the kitchen, then sprinkle them evenly over my compost every week. Those grounds are slightly acidic, which can benefit acid-loving plants (like strawberries, native to Europe and North America) when the finished compost is applied. After a month, I always spot tiny cohorts of ground beetles and rove beetles hunting in the cooler, darker pockets formed by those coffee-rich layers.
Tea leaves—bagged or loose—also break down rapidly and similarly boost nitrogen levels. Just make sure the tea bags themselves are compostable: some contain nylon or polypropylene that won’t decompose. I once added an entire stash of mesh tea bags, only to find those plastic particles drifting through my finished compost months later—a rookie mistake! Now, I remove tags and staples and break apart any paper-based tea bags before tossing them in. The result? Fungal hyphae colonize the tea layers, attracting mites that feed on fungus, while earthworms burrow in and carry those rich nutrients down into the deeper compost layers!
Keep Out Diseased or Infested Plant Material
Indoor summer gardeners know the frustration: you spot powdery mildew on a climbing cucumber’s leaves (Cucumis sativus, native to South Asia) or bacterial leaf spot on your pepper plants (Capsicum annuum, Central American origin), and the urge is to toss the infected foliage directly into the compost. Resist that urge! Pathogens like fungal spores and bacterial cells can survive typical backyard compost conditions and later reinfect healthy plants. I learned this the hard way when a string of downy mildew lesions on lettuce scraps re-emerged in my subsequent batches of microgreens—such a headache! To avoid this, bag diseased plant material (including tomato leaves with early blight) and dispose of it in the trash or burn it where allowed.
Similarly, if you pull up root vegetables like carrots (Daucus carota, native to Europe and southwestern Asia) infested with root-knot nematodes, or you spot a patch of Japanese knotweed (Fallopia japonica, native to East Asia, highly invasive), don’t let those roots or seeds enter your compost. Invasive species can resprout from tiny fragments; I once tossed a handful of mugwort (Artemisia vulgaris, native to Europe and Asia and invasive in North America) into my bin, only to find half a dozen seedlings sprouting weeks later. Instead, place those in a separate yard-waste bag and take them to a facility that heats the waste sufficiently high—over 140°F—to negate any pest or weed threats!
Use Yard Waste Like Leaves and Grass Clippings Wisely
Dry leaves are one of the best “brown” materials you can add to a compost pile. In fall, I rake maple (Acer saccharum, native to eastern North America) and oak (Quercus rubra, native to eastern North America) leaves into my compost bin, layering them with moist vegetable scraps. Those leaves can shelter overwintering beneficial insects like lady beetles and predatory ground beetles, which later emerge to feast on pests in spring! Just be sure to shred or mow over large leaves first; small leaf pieces decompose more quickly, giving earthworms plenty of surface area to nibble and carry deeper into the pile.
Fresh grass clippings are fantastic “green” materials—it’s tempting to toss them straight from the mower into your composter. However, grass clippings can mat down, creating a thick, dense layer that repels air and traps moisture, leading to anaerobic conditions and nasty odors. I always mix fresh clippings with dry leaves or straw in roughly a 1:2 ratio by volume. That ratio gives me a nice balance: moisture-loving springtails and microarthropods move freely, munching through the layers, while fungi colonize the grass and decompose it at just the right rate. If you have treated grass (e.g., recently applied herbicides), wait at least four mowings before composting those clippings to ensure all chemical residues have dissipated.
Add Eggshells and Avoid Excessive Citrus
Eggshells—washed and crushed—provide calcium, which strengthens plant cell walls, reducing the chance of blossom end rot in tomatoes or peppers. I save shells in a jar, rinse them thoroughly to prevent attracting ants or small rodents, then crush them with the back of a spoon before sprinkling them into my bin. Those crumbly shards also create tiny air pockets, improving aeration and deterring slug or snail nesting. Plus, lime-loving earthworms relish the calcium boost and tunnel eagerly through shell-rich layers, carrying nutrients down as they go!
Citrus peels, on the other hand, can be tricky. A moderate amount of orange or lemon peel adds beneficial nutrients, but too much citrus can acidify the pile excessively—pushing pH below optimal levels and discouraging earthworms and beneficial bacteria. I once dumped an entire bag of orange peels into my compost—mistake!—and watched the early colonizing worms vacate the scene within days. Now, I add citrus peels sparingly, cutting them into small pieces so they break down more quickly. If you want to include lemons (Citrus limon, native to Asia) or grapefruits (Citrus × paradisi, hybrid of orange and pomelo) from your juicer, ensure you balance them with plenty of “brown” materials like shredded paper or dried leaves to neutralize excessive acidity.
Incorporate Small Woody Debris, But Avoid Large Logs
Small prunings—like rose clippings (Rosa spp., native to Europe and Asia) under a quarter-inch thick—are fine to add because they break down relatively quickly, especially when mixed with nitrogen-rich scraps. These woody pieces provide structure, creating air channels that help aerobic bacteria thrive. I love adding clipped stems from my lavender (Lavandula angustifolia, native to the Mediterranean), as the fragrant oils boost beneficial microbial activity. Just cut the stems into two- to three-inch lengths so they decompose faster and don’t create long-lasting woody lumps in your compost.
However, avoid tossing in large logs or thick branches—these take ages to decompose and can monopolize nitrogen, slowing down the entire composting process. If you have limbs over an inch thick, consider chipping them first or saving them for a separate wood chip pile. Those wood chips, once aged, can eventually be used as mulch, but they need their own space to decompose and shouldn’t hog the main compost bin. If you add too much fresh wood, you’ll notice the pile struggles to heat up: beneficial thermophilic bacteria won’t activate effectively, meaning fewer heat-loving predators like predatory mites and beneficial nematodes to keep pests in check.
Avoid Diseased or Pest-Infested Produce
Finding a wrinkled, spotted apple (Malus domestica, native to Central Asia) or a tomato with blossom end rot can be disheartening, and it’s tempting to toss all blemished or pest-eaten produce into the compost. Resist the urge! Diseased fruits—particularly those with gray mold (Botrytis cinerea) or blight lesions—can harbor pathogens that survive cooler compost piles, only to infect your potato plants (Solanum tuberosum, native to the Andes) next season. Similarly, if a zucchini (Cucurbita pepo, native to the Americas) falls victim to squash vine borer larvae, those larvae can pupate in the compost and emerge to attack next year’s crop.
Instead, discard any produce showing clear signs of disease or insect damage in the regular trash or municipal yard-waste program (if permitted). If you want to compost these materials safely, consider using a hot composting system that consistently reaches at least 140°F for several days, which can kill most pathogens and insect eggs. In more temperate backyard bins that rarely exceed 120°F, though, you’re better off keeping diseased or infested items out. This extra step can save you the headache of reinvigorating an insidious pathogen cycle or supporting a population of squash vine borers that will return to haunt your garden!
Include Wood Ash Sparingly
When you stoke your wood-burning fireplace or outdoor pizza oven, the resulting ash can be a valuable source of potassium and calcium—two essential nutrients for healthy plant growth. I carefully sprinkle a handful of cooled, sifted ash onto my compost heap in late fall, mixing it thoroughly with “green” materials like fallen grass or kitchen scraps. That tiny bit of ash raises the pH slightly and boosts mineral content, making the final compost ideal for acid-loving plants like blueberries (Vaccinium spp., native to North America) or rhododendrons (Rhododendron spp., native to Asia).
However, caution is key: too much ash can make your compost overly alkaline, which unwelcome critters like earthworms and predatory beetles avoid. I once overdid it, and the part of my pile nearest the ash became eerily free of the usual army of compost-dwelling insects, indicating pH was out of whack. To avoid this, limit ash additions to no more than one cup per cubic foot of compost, and always mix it deeply to prevent localized pH spikes. If you’re collecting ash from fruitwood—like applewood (Malus domestica) or peachwood (Prunus persica)—expect slightly higher sugar residues and scent, which may attract ants momentarily, but these usually dissipate once the ash is well integrated.
Don’t Compost Pet Waste or Diapers
It’s tempting to toss pet hair, soiled cat litter, or dog feces into a compost bin to cut down on waste, but that can present health hazards. Pet waste—especially from dogs (Canis lupus familiaris)—often contains pathogens like E. coli or roundworm eggs (Toxocara canis) that won’t reliably break down in typical backyard compost conditions. Likewise, diapers (cloth or disposable) can shelter harmful bacteria and often contain plastic or synthetic polymers that resist decomposition. I learned this after noticing my toddler’s cloth diaper liners still intact months later, even in the hottest days of summer—definitely not compostable!
For rabbits (Oryctolagus cuniculus) or chickens (Gallus gallus domesticus), some people compost bedding and droppings in separate bins to create specialized manure compost—provided it heats above 150°F to kill pathogens. But unless you have the space and commitment to a dedicated hot composting system, it’s safest to dispose of any pet waste and diapers in the household trash. By keeping these items out of your vegetable compost, you safeguard against potential disease transmission, ensuring that earthworms, beneficial mites, and predatory beetles in your bin remain as healthy allies in breaking down organic matter.
Incorporate Non-Invasive Plant Trimmings
I love adding pruned stems of lavender (Lavandula angustifolia, native to the Mediterranean) and rosemary (Rosmarinus officinalis, from the Mediterranean region) to my compost heap—they’re fragrant and break down nicely if cut into small pieces. Those aromatic herbs not only add carbon but also help repel certain pests in the compost pile itself. Similarly, fallen petals from native flowers like coneflower (Echinacea purpurea, native to North America) and black-eyed Susan (Rudbeckia hirta, native to North America) feed beneficial pollinators—even in the compost—because small mason bees sometimes nest in those wilted flower heads before they disintegrate entirely.
Be cautious when composting clippings from plants listed as invasive in your area—like Japanese knotweed (Fallopia japonica, East Asia origin) or burning bush (Euonymus alatus, East Asia origin). These species can regrow from tiny fragments if not fully decomposed. I once tossed a few small knotweed stems into my backyard bin, and the next spring, several new shoots emerged from under the bark-layered mulch—lesson learned! If you have invasive plant trimmings, either cut them into pieces smaller than one inch and ensure the pile reaches at least 145°F for a sustained period, or bag them and send them to a green-waste facility that handles invasive species. This way, you keep your garden—and your compost—both productive and ecologically responsible.
Balance Greens and Browns for Proper Nitrogen Levels
A well-balanced compost pile relies on both “greens” (nitrogen-rich materials) and “browns” (carbon-rich materials). Kitchen scraps, coffee grounds, and fresh grass clippings are your primary greens, while dry leaves, shredded newspaper, and small wood chips serve as browns. Too many greens create a slimy, smelly pile that attracts fungus gnats and slugs (with some slug species like Arion vulgaris being invasive in some regions), while an overabundance of browns slows the decomposition process to a crawl. I aim for roughly a 1:2 ratio by volume—one part greens to two parts browns—to keep microbial activity balanced and avoid creating conditions that repel earthworms or inhibit thermophilic bacteria.
When layering your compost, sprinkle greens evenly between thin layers of browns to maintain airflow and moisture balance. If your pile starts emitting ammonia odor, that’s a clear sign of excessive nitrogen—add more shredded paper or dried leaves to soak up the excess. Conversely, if little decomposition is happening after two months, it may be too carbon-heavy; sprinkle in some fresh grass clippings or vegetable scraps to kickstart microbial communities. With practice, you’ll learn to judge the consistency, color, and smell—ultimately supporting a robust ecosystem of beneficial nematodes, predatory mites, and beetles that keep your compost teeming with life and ready for use!
Protect Your Compost From Excessive Moisture or Drought
Rainstorms and irrigation can turn a well-aerated compost pile into a soggy swamp, driving out beneficial organisms and inviting anaerobic bacteria that produce foul odors. If your compost is soaking wet, cover it with a tarp during heavy rains or consider moving it under a shed overhang. I remember one torrential downpour that turned my meticulously layered bin into an anaerobic mess—smelly, slimy, and virtually void of worms. Once I recovered by flipping the pile, adding dry leaves, and giving it a day to drain, I restored that balance and attracted a flotilla of earthworms and sowbugs eager to get back to work.
During summer droughts, indoor gardeners often forget that compost bins need moisture to keep microbes active. If your area is experiencing a heatwave, I recommend giving your pile a gentle sprinkle every few days—aiming for the moisture level of a wrung-out sponge, not a mud puddle. This modest hydration helps springtails and beneficial beetles stay active as temperatures climb. I store a small watering can near my bin so I don’t have to trek back and forth from the tap; a few gentle pours after a week of hot, dry weather is usually enough to maintain activity. By protecting against both extremes—flood and drought—you’ll sustain the robust microbial and invertebrate communities that turn your scraps into crumbly, nutrient-packed compost!
