Grow medium is an integral part of any gardening operation be it and outdoors garden or a few plants in planter on your windowsill, because the growing medium is the thing that provides your plants with nutrients and other substances your plats need to grow. And those, who are avid indoors gardeners or container gardeners know the struggle of wanting to reuse their grow medium for their next batch of plants, but not knowing if it is a good idea. So lets discuss reusing your grow medium and should you even do it.
First things first, I have to say that both soil and other growing mediums can be recycled and reused. You just have to know how to do it, since it probably wouldn’t be advisable to just pluck out your old plant and plant new one in the same soil right after. That is because the soil usually becomes infused with different nutrients when plants grow in it, so before you go and reuse your potting soil for your next grow, you should flush it thoroughly. Use a nutrient flush solution and flush your soil a couple of times, so you can be sure that the soil doesn’t have excess salts or other nutrients in it from the last grow, that can not only harm your plants but also mess up your nutrient schedule and your plant’s growth.
But extra nutrients isn’t the only thing you need to watch out for, when you are thinking of reusing your soil, 
you should also be wary of different diseases that might be hiding in the soil. Some of the most damaging and hart-to-get-rid-of plant diseases actually live in the soil. For example, both powdery mildew and root rot are soil born plant diseases. So if you are thinking of reusing soil, but the previous plants that were in it had one of these diseases, then I would suggest to better just buy a new potting mix. Better safe than sorry. But if that really isn’t an option, you can still recycle and reuse the soil, you just have to allow your soil a resting period. After flushing the soil, put in a sunny place, let it dry out completely and then leave it to rest for a while. This process will make sure that the spores of these soil-borne diseases will die off and won’t infect the next plants that you use that soil on.
Additionally, you should also not only remove the old plant from the soil that you are thinking of reusing, but you should also try to get all of the old roots out of the grow medium. This will make sure that your soil has nice and healthy texture for you next plants. You can even add some fresh potting mix to the old soil, which will be better for your plants and give them some fresh, natural nutrients to feed on.
Finally, when your old soil is ready for reuse, you can plant your plants in it again. Just make sure to not only water the plants that you plant in the recycled soil well, but also to fertilize them, so they get all the nutrients they need. By fertilizing them I mean not only once the plants are already in their pots, but also during the actual planting process. This will help the plants to adjust to their new environment faster, as well as will encourage their growth and reduce the stress that plants go through, when they are planted or re-potted. On top of that, by feeding plants nutrients upon planting them, it will also make sure, that, even if you didn’t flush your soil good enough, the plants will still get all of the nutrients they need to grow properly.
