Can You Reuse Potting Soil? Yes, in many cases, you can reuse potting soil. However, you do need to prepare the soil first by removing pathogens and re-introducing nutrients. The soil is also viable if the plant it housed didn’t die from a pest infestation or disease.
Quality potting soil is vital if you want your houseplants to not only live but also thrive.
Unfortunately, high-quality soil is far from dirt cheap. To save money, you can reuse potting soil, but only in certain conditions.
Here’s a closer look at the feasibility of reusing potting soil mix for succulents, flowers, cacti, and other indoor plants.
Related: Does Potting Soil Go Bad?
Potting Soil Explained
Surprisingly, potting soil doesn’t contain any dirt. It’s a mix of moss, bark, peatmoss, sand, fertilizers, and more designed to resist mold, allow for efficient drainage, and help plants grow. It’s specifically made for use indoors.
Potting soil doesn’t last forever. As plants grow, they pull nutrients from the soil. Also, water washes away nutrients over time. However, you can replenish the soil as necessary.
Reusing potting soil alone won’t sustain a plant. However, you can mix it in with new potting soil. Replenishing your potting soil will save you in the long run because you have to buy less new soil.
What Conditions Damage Potting Soil?
Can you reuse potting soil in every instance? No. Only potting soil in particular conditions will work.
The most significant factor in how effectively you can reuse potting soil is what happened to the plant that used to be there. Watch for these potential problems:
- Insects and Pests
If the plant died due to those cases, the soil mix is not a good candidate for rejuvenation processes. Those same issues will likely occur to the new plant. However, if you want to move a healthy plant out of a pot, or you have a plant that died due to a different problem, then you can try to use the soil for something new.
Sterilizing Your Recycled Soil
Your first step is to sterilize your potting mix. It removes any potential threats such as disease pathogens, bugs, eggs, or weed seeds. Sterilizing can’t remove a massive pest infestation or a tangled root ball, but it can successfully eliminate minor amounts to make the soil safe to use.
Two sterilization options are available
First, the sun works as an effective sterilizer. Put your soil in black plastic bags or covered buckets. Next, place the bags or buckets outside in the direct sun for four to six weeks. The sun will raise the soil temperature and kill a host of potentially troublesome organic matter.
Check out our article on Solar Sterilization of Soil
Oven-based sterilization is also called pasteurization. It allows you precise control over the temperature, and it’s available year-round.
Place four inches of soil in a pan. Cover it with aluminum foil. Insert a meat thermometer to monitor the internal temperature.
Bake in the oven at 180° degrees Fahrenheit for 30 minutes. Afterward, remove the soil and allow it to cool. Keep it covered during the cooling period, which should last about half an hour or so.
Note that precision matters here. Bake the soil at precisely 180° degrees. If used soil is allowed to bake at 200° degrees or higher for any significant amount of time, it can release toxins.
NOTE: If you try “cooking” the soil, be prepared for a smelly house!
Sterilize Pots and Tools
Pathogens and other problems aren’t just found in soil. They can also transfer to your new plants through contaminated tools and pots. Wash everything thoroughly in a solution of one part bleach to nine parts water.
Let each pot, tool, etc. soak in the solution for 30 minutes.
Rinse and dry them thoroughly to avoid bleach build-up and mold growth.
For terra cotta pots, soak them in clean water for at least 10 minutes to remove all bleach traces.
Potting soil loses its nutrients over time, so you’ll need to add fertilizer before using the soil again. You have two options. Add slow-release fertilizers that will last for an entire season. You can also add liquid plant fertilizer approximately every two weeks
You’ll also want to add vermiculite. It’s a yellow/brown mineral that retains moisture efficiently, which helps indoor plants grow.
Finally, you can add fresh compost. However, because compost is so dense, you don’t want to use too much of it. Use one part compost for every four parts of fresh potting soil.
Blend With New Soil
Once you’ve pasteurized and fertilized the potting soil, you’re ready to put it to use. Blend it with a mixture of new potting soil. You want to use an equal amount of each.
Can You Reuse Potting Soil More Than Once?
If the soil meets the conditions above and can adequately rejuvenate it, you can use potting soil multiple times. However, the more times you reuse it, the more new fresh soil you’ll want to add.
How To Store For Soil During Winter
Storing your potting soil properly helps keep it in good condition for repeated use. Store the soil in garbage cans, clean containers, or buckets. Keep them out of winter weather as much as possible. Storing them in a dry garage will typically keep them protected.
Final Thoughts For Healthy Soil
Can you reuse potting soil? Yes, but it does require a specific process to work correctly.
Potting soil can’t be used indefinitely, but it can successfully support several plants. As long as the soil contains no pathogens or roots, you can sterilize and fertilize it for further use.
While you’ll always need a certain amount of new soil to keep your plants alive, reusing old soil is an effective and easy way to keep costs down.