How To Reuse Old Potting Mix To Improve Your Garden's Clay Soil

If your plants are saying "nay" to the clay soil that surrounds them, it's time for a garden refresh. Soil that has too much clay in it makes it difficult for plants to grow to their fullest potential for several reasons. Clay tends to retain moisture for a long time because it's so dense, plus it doesn't drain as well as a sandy or loamy garden soil. It's harder for plant roots to penetrate clay soil, and even if they do, it's difficult for ever-important air to reach those roots. 

Correcting the too-much-clay issue is often just a matter of adding organic matter to the soil and mixing it in. One material that's handy for this purpose is old potting soil. Save that soil after potted plants die, or when there's potting mix left over after transplanting seedlings. As long as the used potting soil still smells fresh, isn't compacted, and hasn't housed diseased plants or plant pests, you can repurpose it as an amendment to the clay soil in your garden. Old potting soil that's in good condition can also help your raised garden bed thrive. 

It's best if you are able to amend all of the garden soil at once if it contains too much clay, but in a pinch, just amend the areas where you're about to add new plants. Dig a hole about three times as deep and wide as the plant requires, and transfer the scooped-out dirt to a sheet of plastic or cardboard. Dump the potting soil near the dug-out soil and mix the two together. Add a little of the mixture to the hole, then set in the plant or seedlings. Fill the rest of the area in with the mixed soil.  

It's worth noting that used potting soil won't have the same nutrients in it as fresh potting soil, but it will make the garden's soil less clay-dominant. A mason jar comes in handy to test the composition of your amended garden soil to determine how much clay is still in it by volume. The ideal garden soil is loamy, which means it has nearly equal amounts of clay, silt, and sand. Loamy soil retains enough moisture while still draining well, and many garden plants prefer such conditions. 

To give the new garden soil a boost, mix some compost into it as well. Compost acts a bit like a fertilizer in the soil. It makes the soil less clay-heavy while increasing the available nutrients in the soil, making it healthier for the plants. Adding other forms of organic matter, such as decayed leaves, peat moss, and straw, will also help improve drainage and reduce compaction.