Thursday, April 9, 2020

Can I Compost my Potting Soil?

Last year I made a container garden for my herbs. I planted the seeds with store-bought potting soil and enjoyed them for the season. As I cleaned up my container from last year, I headed over to the compost bin and was about to dump the entire container in, when something caught my eye... those little white balls in the soil. I had no idea what these were or if they could go into my compost bin, since they resemble mini balls of Styrofoam.

So I did some digging... These little white balls found in store-bought potting soil are called perlites. Perlites are naturally occurring minerals found in soil, aiding aeration and drainage for plants. And for our use, YES you can compost them along with your potting soil! 
Guest Blogger and Composting Coach, Angela Rivera


  1. Angela, that is a maybe. If you can crush those balls between your fingers, it is perlite. If they just return to their form, they are likely Styrofoam balls, which do not compost. For many years, the nursery industry used a mix of Styrofoam balls, peat moss and fertilizer for potted plants because that mix weighed much less than real soil. In that industry, heavier weight means higher shipping costs.

    The really bad thing the potting mix in which most plants come is that it dries out rapidly and the drier it gets, the more difficult it is to get wet. One of the first things a person should do when purchasing a plant growing in this potting mix is to repot the plant in a much more decent soil.

  2. I am curious about what to do with weeds and sod, especially now that Hamilton County is not picking up yard waste. I’ve read before not to compost weeds to avoid incorporating seeds from the composted weeds into your garden. I’m doing some major sod removal and weeding this spring and have it all in a big pile in a corner of my yard, but am not sure what to do with it. I just wanted to check here to see if it’s completely correct that neither could be composted.

    1. Good morning Miss Maple, composting weeds is a personal preference. I, personally, love composting weeds because it adds a boost of nitrogen and more material to my compost = more finished compost. You cannot guarantee that the compost will get hot enough to kill the weed seeds though so you may plant the weeds with the finished compost. In my opinion every breeze moving through my yard is planting weed seeds though. An alternative is removing seed pods and composting the green material.

      Hamilton County does not collect yard trimmings from any community, that is up to the city/village/township where you live. We do have yard trimmings drop offs- two of which are still open during the stay at home order. If you can just hold onto it in a corner of your yard and bring it later in the year, that is what we recommend.

      Sod is compostable! Defintely add that to your pile. Or you can offer it up to some neighbors on NextDoor if it is replantable.