Those of you who love plants have probably jumped over a similar hurdle.  Maybe you tried to overwinter a tomato plant and it eventually gave up the ghost, or you have a house plant that was potted up into a larger containetr, leaving some soil behind.  Either way, you're left with dirt from which the nutrients are mostly gone, but with plenty of yummy organic matter left.

The best use of old potting soil depends in part on your house plant style, and on what kind of mixture you started with.  In the most typical scenario, you bought potting soil from the big box store and you use chemical fertilizers to feed your plants.  In this case, you might as well reuse the potting soil since you're basically growing your plant hydroponically, using the potting soil as a structural element only.  You might want to mix the old potting soil half and half with high quality compost or new potting soil, though, to add a few nutrients to the earth.

(As a side note, if your plant died from something soil related, you won't want to reuse the troubled dirt as is.  Some gardeners report good results with sterilizing the soil by pouring boiling water over it, or by baking the soil in the oven.  Finally, you could simply add the potting soil to the outdoors garden, where beneficial microorganisms will make short work of the bad guys.)

At the other extreme, you might make your potting soil out of a mixture of compost, stump dirt, or other organic materials like I do.  In this case, your potting soil is providing the nutrients as well as the structural components, which is why you'll need to topdress your potted plants at least once a year and to cut away part of the roots of long-lived plants to replace some soil lower down.

In this homegrown scenario, depleted potting soil should head out to the garden, where it will act as a soil amendment.  I dumped mine between logs in a hugelkultur bed, but you could also apply the old potting soil to the top of a bed in the vegetable garden or alongside a tree mound that needs to be expanded.  The soil is probably low in nitrogen, but is unlikely to be low enough that it will grab nitrogen out of nearby earth.  Instead, it will help fluff up your garden soil, increase its water retention capacity, and make microorganisms happy.

(By the way, thanks for cleaning up the office, honey!)

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About us: Anna Hess and Mark Hamilton spent over a decade living self-sufficiently in the mountains of Virginia before moving north to start over from scratch in the foothills of Ohio. They've experimented with permaculture, no-till gardening, trailersteading, home-based microbusinesses and much more, writing about their adventures in both blogs and books.



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