To my fellow frugal gardener
Many times over the years I’ve been asked if old potting mix can be reused. I base my answer to this question on my personal experience. I have found that as long as I am sure that the plant in a container from the previous year had not died of insect or disease damage the soil is perfectly fine to reuse. That being said; I do have some recommendations for those who choose to do this. Keep in mind that a container of old soil mix is depleted of its nutrient value. Frequent watering has leached out any nutrients and fertilizer that was contained in the original mix when it was fresh. The easiest way to reuse old potting mix is to empty all of your containers into one large container. An old trash can, wheel barrow, or large pot will work fine. Then add fresh compost or manure at a ratio of one part fresh to three parts old. If you are using fresh potting mix instead of compost you can mix at the rate of 50/50. It is a good idea to add some form of fertilizer to the mix as well. I prefer dried corn gluten meal. But kelp, worm castings, or fish emulsion are also good choices. Mix thoroughly then moisten slightly and you will be ready to plant.
Note: If you prefer to be on the safe side you can sterilize your soil in the oven (this will kill any residual disease or insects.) Preheat @ 350 degrees, place soil in a shallow, oven safe dish, and bake for 20-30 minutes. Allow soil to cool then mix with fresh soil as we mentioned earlier. Money saved on potting mix will mean more to spend on plant material! Happy Spring planting, everyone!