Should I reuse this potting soil? - Ask Extension
I planted some bulbs in potting soil this spring, just to see what would happen if I planted them in the spring vs fall. The bulbs have not developed ...
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Should I reuse this potting soil? #864916
Asked April 17, 2024, 5:40 PM EDT
I planted some bulbs in potting soil this spring, just to see what would happen if I planted them in the spring vs fall. The bulbs have not developed and have mold in them. Can/should I reuse the potting soil that has had molded bulbs in it? Thanks!
Juneau County Alaska
Expert Response
Hi Sally,
Reusing potting soil is a common practice that growers do and it's a matter of what you will reuse it for and what is the acceptable risk you have. In your case, my decision would be to NOT use it for starting seeds because used potting soil will more likely have higher numbers of "damping off" causing organisms. I only use new, bagged soil for that (though I know folks who are successful with well composted media for starts).
The mold formed on the outside of your bulbs is likely "saprophytic" which is just consuming the dead outer leaves of the bulbs and is beneficial in soils to release nutrients which your plants can use (or be consumed by soil bacteria and other organisms which also release useful nutrients).
If you had planted the bulbs in a scenario in which it was thought that they rotted due to disease, I'd be hesitant to reuse it at all (to prevent potential spread of any disease), but in the scenario you have described, I think a safe reuse of that potting soil is to put it in to a garden bed (not a bulb bed) or compost pile. In that environment, there will be strong competition from other organisms and if managed properly, the "good guys" will outnumber and out compete the "bad guys".
BTW- the other times I am really careful not to reuse potting soil is if the previous plants have had known infestations of root maggot or slugs which can persist in the soil to the next year.
Reusing potting soil is a common practice that growers do and it's a matter of what you will reuse it for and what is the acceptable risk you have. In your case, my decision would be to NOT use it for starting seeds because used potting soil will more likely have higher numbers of "damping off" causing organisms. I only use new, bagged soil for that (though I know folks who are successful with well composted media for starts).
The mold formed on the outside of your bulbs is likely "saprophytic" which is just consuming the dead outer leaves of the bulbs and is beneficial in soils to release nutrients which your plants can use (or be consumed by soil bacteria and other organisms which also release useful nutrients).
If you had planted the bulbs in a scenario in which it was thought that they rotted due to disease, I'd be hesitant to reuse it at all (to prevent potential spread of any disease), but in the scenario you have described, I think a safe reuse of that potting soil is to put it in to a garden bed (not a bulb bed) or compost pile. In that environment, there will be strong competition from other organisms and if managed properly, the "good guys" will outnumber and out compete the "bad guys".
BTW- the other times I am really careful not to reuse potting soil is if the previous plants have had known infestations of root maggot or slugs which can persist in the soil to the next year.
