A Gardeners Forum Forums Gardening Reference Gardening in 2004 Reusing potting soil

Is it EVER a good idea to reuse potting soil? :rolleyes: I've seen people whose plants have died or they just repotted and keep the old soil. I know to reuse it if you're repotting a plant; just didn't know if it's okay to keep it and use it mixed with new soil to pot other plants.

I use it for potting up larger plants or transplanting plants from cell packs to hanging baskets but never for starting or transplanting seedlings. I always mix some fresh fertilizer in and sometimes even some perlite.

If you bake your used potting soil in the oven it will sterilize it for you. Preheat oven to 200 degrees. Place used soil mix into a turkey sized baking bag & place on a large cookie sheet, laying the bag sideways and tucking the open end under. Poke several holes in the top, then place a meat thermometer in the center. Set oven from preheat to bake, place cookie sheet with soil into oven. When the internal temp reaches 180 degrees, leave in oven for another 30 minutes. This will bake most organisms that can cause seed germination failure & dampening off, as well as killing any seeds that might be left over in the used soil.Though nutrients can be lost. The use of baking bags can curtail the unpleasant odor of baking soil. Remember, the seedlings really don't need any nutrients in the soil until they establish true leaves, since nutrients are supplied by the cotyledons (first leaves)until then. If you are not using the sterilized soil for seedlings, but rather established plants, just use a proper fertilizer to re-nutrient the soil, and compost works wonders too:) Hope this helps, Chrissy

There is some risk in reusing potting soil. Fungius spores and dormant plant pests might be in the soil. The risk is probably low, but if you can afford to use new soil and discard the old, you might be better off.

i add my "used" soil to the compost bin, to the raised beds outside (the ones i am just starting) and to plants that i know are healthy and hardy. i use fresh potting soil for everything else. usually, if i have a plant die, it is because i forgot to water it on its schedule, so my "used" soil is really to dry to do anything with!

I'm cheap, I container gsarden and keep all my soil, the freezing in the large plastic garbage can is my assurance the bugs are now composting my soil, I do add the most slimy soils to my compost bins. I then mix the soil with new potting soils in the spring, and sand, peat, manure etc....
The interior soils are only reused in the inside, I don't want bugs from outside making themselves 'at home' as it were.....mostly I've had no troubles, the old roots left behind kind of compost my potting soils indoors.

Pl