We wouldn’t call container plants fancy, but they do like to hang out in soil that makes every day seem like a spa day. Who can blame them? With its lightweight texture and flair for regulating moisture, potting mix just nurtures potted plants in all the right ways. The good stuff doesn’t come cheap, though, so at the end of the season you may be left wondering: Can you reuse potting soil? With a little prep work, you sure can—and it’s not hard to do, either.
How to Sterilize Used Soil
The first step in reusing old potting mix is to sterilize it. You want to prevent damping off, a disease caused by soil-borne fungi, as well as stop any other bacteria or pests that were planning to linger around till next season. (Even with sterilization, though, you want to avoid reusing soil that housed a diseased plant or one with major insect issues. It’s best to throw it out and start over in this situation.)
One of the easiest ways to sterilize potting mix that’s still in good shape is through solarization, a simple method that lets the sun do most of the work. Your part includes gathering all of your used potting mix into heavy-duty plastic bags, tying them shut, and then finding the sunniest part of your yard to stash them.
If you’re starting this process at the end of the growing season, you’ll need to store the bags in a sunny spot until spring rolls back around. (Pro tip: Add another layer of plastic to help increase the soil temp.)
How to Store Used Soil
Clean, airtight storage bins are the best friend to any potting mix you plan to keep in reserve. A sparkling interior is key—you don’t want to put sterilized soil in a potentially contaminated container. If your storage solution isn’t new, grab a scrub brush and follow these steps to wash it. While you’re at it, do the pot your plant was in and any tools you used, too.
Fill the storage bin with a cleaning solution that’s 1 part bleach to 9 parts water.
Let it soak for 30 minutes.
Dump most of the water—keep a little bit to help scrub the bin clean from top to bottom. (Always safely dispose of bleach by pouring it down a drain, not onto the ground.)
Remove any remaining water and spray the bin with a hose.
Make sure the bin is completely dry before adding any potting mix to it.
Once your bin is clean, dry, and filled with potting soil, make sure the lid is on tight and then store it away from the elements, like in the garage, until you’re ready to get growing again.
How to Revitalize Used Soil
If there’s a downside to soil sterilization it’s that it kills off everything living in the soil—the bad and the good—so you’ll need to give your potting mix a nutritional boost before putting it back into action.
One option is to add (fully-decomposted) compost to your sterilized soil. Add one part compost to three parts potting mix. You don’t want to overdo it with the earthy goodness, so that ratio is important—although compost is chock full of nutrients, it has a tendency to become compacted and can block the flow of air and water to plant roots if you have too much in a pot.
That’s it! Once your potting mix is ready for your plants once again, you can get out there and start growing. Soon you’ll have a whole container garden full of blissed-out veggies, flowers, and herbs. Cue the spa music.