Yes, you can reuse old succulent soil if you treat it the right way first. Start by checking for pests and disease signs. Clean soil from healthy plants just needs some fresh grit added back in. Soil from sick plants should go in the trash to avoid spreading problems.
I tested this method on soil from my healthy jade plants last year. The mix came out fine after I baked it and added fresh perlite. But when I tried to save soil from a plant that died of root rot, the next plant in that pot got sick too. Now I always toss soil from problem plants without trying to save it.
You'll want to sterilize old soil before using it again to kill any hidden threats. Spread the soil on a baking sheet about 2 inches (5cm) deep. Heat your oven to 180°F (82°C) and bake for thirty minutes. This kills fungus spores, pest eggs, and weed seeds that hide in the mix.
The smell from baking soil can get pretty strong in your kitchen. I suggest opening a window and running your vent fan while you work. Some growers do this step in an outdoor grill instead. The results work just as well and keep the smell out of your home.
Let your soil cool down before you add anything to it or pot up your plants. Hot soil can damage roots on contact. Spread it out on a tray for an hour or two until it reaches room temperature. This step also lets extra moisture escape from the heating process.
To rejuvenate succulent soil that has broken down, add fresh mineral parts back in. Mix in 25-50% new perlite or pumice to restore the drainage your mix has lost. The original grit gets crushed over time and packs together. Fresh chunks bring back the air flow your roots need.
When I first started reusing soil, I skipped the fresh grit step. The mix looked fine but drained slow. My plants started showing stress within a month. Now I always add at least one part new perlite for every two parts old soil to keep things draining fast.
Some growers skip the oven step and just add amendments to their old soil. This works if your plants were all healthy and you saw no signs of bugs. But if you had any problems at all, take the time to sterilize old soil before you use it again.
Store your treated soil in a clean dry container until you need it. A bucket with a lid works great for keeping things fresh. Label the container so you know what's inside and when you made it. Use up your stash within a few months for best results.
Not all soil is worth saving in the end. Mixes that smell bad or show mold growth should go in the trash. Soil from plants with root rot carries the fungus that killed them. Saving a few dollars on soil isn't worth losing another plant to the same problem.
Read the full article: Ultimate Succulent Soil Mix Guide
