What Should I Feed My Compost?

You know the saying: Compost happens. That’s true, in a sense; grass clippings, kitchen waste, chicken litter, leaves, and even paper tossed together will decompose into a nutrient-rich soil amendment. But compost is also a living bioenvironment that requires some ground rules.

We asked our compost guru, Senior Horticulturist Andrew Miano, about what you shouldn’t – and should – put in your compost.

What SHOULDN’T I Compost?

• Bioplastics and cardboard products. While many new bioplastics are marketed as biodegradable, “they can require an industrial-style facility to biodegrade them properly,” Andrew said. “Your home compost system won’t do it.” Likewise, he says, even cardboard products that claim to be printed with plant-based inks may contain ‘forever chemicals’ that could linger in the compost and be inadvertently spread to your garden plot and raised beds and harm the beneficial microbes in your soil. He recommends recycling these products instead.
  
  
• Produce stickers. When adding vegetable or fruit peelings to your compost, be sure to remove all stickers first. “They’re commonly forgotten about,” Andrew says, “but they are made from a non-biodegradable material. It will not break down and you’ll get too much trashy material in your compost.”
  
  
• Animal products. Andrew cautions against adding bones, skin, or pieces of meat to the compost. “They can draw flies and other nuisance insects,” he said. “In a rural setting, you may also have critters getting into your compost and making a mess.” Andrew recommends sending meat scraps to the garbage instead.
  
  
• Fecal matter from domestic animals. Though people often add chicken or rabbit poop to compost, Andrew warns against dumping Fluffy or Fido’s droppings. “It can cause a health risk if it’s not properly composted,” he says. “There are things like salmonella and listeria that could linger in your compost if it doesn’t get hot enough. And it can make your compost extremely unpleasant to smell.” Dispose of it in the garbage instead.
  
  
• Diseased plants or persistent, seedy weeds. “If your compost doesn’t get hot enough – if it’s slow and cool – the weed seeds will survive,” Andrew said. “Some weed seeds will survive being set on fire.” A better-safe-than-sorry approach to composting diseased plants prevents spreading those diseases to healthy plants. Additionally, you might end up accidentally spreading an invasive plant, so it is better to dry weeds and diseased plants and burn them or put them out with the garbage, Andrew says.
  
  

What SHOULD I compost? 

Short answer: Lots of things. First off, Andrew says, aim for a good balance of “green stuff and brown stuff; I’ve found that a good 50/50 mix in a lasagne layering does just fine.” Greens are rich in nitrogen and protein; browns are rich in carbon or carbohydrates.  

• Kitchen scraps. The kitchen is a treasure chest of material for compost heap, from peelings and coffee grounds to meal scraps that don’t include meat, dairy, or fats. (These take much longer to break down, and they stink and attract animals.) Kitchen scraps fall into the ‘green category,’ which help to heat up the compost and feed microorganisms that contribute to decomposition.
  
  
• Grass and garden clippings, pine needles, wood chips, tree bark, and spent garden plants. This recommendation comes with an important caveat: Do not use clippings from lawns treated with RoundUp or other chemicals, and do not compost diseased plants, Andrew says.
  
• (Some) paper products. Paper can be good if you need to bulk up the compost and create some habitat for soil-dwelling creatures like earthworms. However, Andrew cautions to avoid adding paper products that have glue, stickers, or tape on them. These won’t break down, and they also may contain chemicals you don’t want in your garden. Look for newspapers printed with soy-based ink, and don’t use glossy paper, such as that used to print magazines and mailers. (And you can always add extra worms to the pile.) 
• Comfrey. “Comfrey is a great compost stimulator because it’s able to pull nutrients out of the soil by going deeper than other plant roots go. It’s best to use a variety such as Bocking 14, which doesn’t set seeds. “Chop and drop it fresh, or collect and dry it,” Andrew says. It doesn’t take much volume to get the compost going.
  
  
• Other biodynamic plants such as yarrow, nettles, and chamomile. These speed up the decomposition process in compost and add nutrients like nitrogen, sulfur, and potassium. Be sure to use dried nettle, not fresh, in the compost. Using biodynamic plants isn’t difficult, but it may be a bit fussy for those who prefer a more hands-off approach. For a basic overview of using these plants, see this article from the Biodynamic Association. 

Other essential composting tips: 

A healthy compost pile needs even moisture.

Keep tabs on the moisture. “Too dry and too wet both have problems that keep compost from reaching an ideal temperature and finishing more quickly,” Andrew said. “Too wet and not turning enough can cause more anaerobic growth, which you will know by the smell when you crack open the pile. Adding more brown material may help in situations where you need to ‘dry out’ the pile some.  

If you live in a wet environment, it's a good idea to use a tarp to cover your pile from getting too much moisture. And those in hot and dry climates may need to "water" your pile sometimes. You can easily set up a sprinkler, so you don't have to stand there for long periods to make sure it's getting down into your pile. The size of the pile may also determine how long or how much water you need on your compost.” 

Turn! turn! turn! your compost! 

Turning your compost regularly is essential. It helps aerate the pile, providing oxygen to the beneficial microbes that break down the organic matter. It also helps distribute heat and moisture. Higher temperatures also help control the growth of weed seeds in the pile. 

Key Takeaways:

• Be choosy about using paper. While it’s a good source of the ‘brown stuff’ in a compost pile, the chemicals in glue, ink, and paper coatings don’t have a place in your garden soil. 
• Avoid using fecal matter, especially from domesticated animals (i.e. dogs and cats).  
• Aim for a 50/50 mix of greens (nitrogen-rich stuff like kitchen scraps and plant material) and browns (carbohydrate-rich material like leaf litter).  
• Explore biodynamic techniques to amend the compost pile. 
• Control moisture, oxygen, and temperature in the pile by monitoring and turning the compost regularly. 

About the Author;

Andrew Miano with 2 Violeta kohlrabis

Andrew Miano is senior horticulturist at Baker Creek Heirloom Seed Co., based in Mansfield, MO. Baker Creek sells only heirloom and open-pollinated varieties and currently offers about 1,000 varieties from around the world. A landscaping job after high school led Andrew to edible landscaping, greenhouse work, and eventually studies in plant science, nursery and greenhouse production and management, and fruit and vegetable production. He leads Baker Creek’s trial growing program and is an expert in organic farming. 

You can always email your gardening questions to seeds@rareseeds.com. Put "hort question" in the subject line, and someone on the horticulture team will get back to you.