As the traditional gardening season comes to an end, we gardeners are finishing up the last of our seasonal chores. One task that easily fills an autumn day in my garden is the deconstruction of all my container plantings.
I grow many different edibles, tropicals, annuals and perennials in glazed ceramic patio containers every year. While the fig and banana trees go into the garage and any perennials find their way into the garden, those containers that housed annuals and frost-tender edibles now need to be emptied before being stacked in the shed for the winter. Leaving them full of potting soil and exposed to the damaging freeze-thaw cycles of winter almost always results in cracked terra cotta come spring.
The quandary I’m always left with after this chore is completed is what to do with all the used potting soil I pull out of them. Potting soil should not be reused for container plantings from one year to the next as the nutrients have mostly been depleted and it may harbor pathogens. Although I sometimes “recycle” a small percentage of my potting soil by amending it with a heavy dose of compost before using it again, most of the potting soil I use is replaced every spring.
But I’m always looking for other ways to use my spent potting soil. Here are four ways to breathe new life into old potting soil.
1. Host A Plant Swap
In years past, I saved a few garbage bags full of my used potting soil every fall and stored them in our shed. In the spring, I used this old soil to pot up divisions of hostas, daylilies and other perennials to share with friends. Because these plants will find a permanent home in a garden, they won’t be in the container long enough to notice the lack of nutrients.
2. Make A Potato Bin
I sometimes pile my used potting soil into a 4-foot-tall, box-wire frame, lined with newspaper. I combine it with shredded leaves, aged horse manure and compost every fall. Come spring, I plant seed potatoes into the top of the wire bin. By the time late summer arrives, I’ve got plenty of spuds to harvest.
3. Make A New Garden Bed
Sheet composting—aka lasagna gardening—is a great way to make a new garden. The technique utilizes layers of organic matter to create a new planting bed right on top of existing sod. To do it, throw down some cardboard or newsprint, cover it with your old potting soil, and then top it with several layers of shredded leaves, untreated grass clippings, aged manure, kitchen scraps, straw and other organic matter. By spring, it will be ready to plant.
4. Compost It
Old potting soil can easily be added to a compost pile, though any small, white pieces of perlite will remain, even after the compost is finished. I’m careful to ensure my compost pile has a good mixture of ingredients to help it decompose at a good clip and create a balanced compost.