6 Things To Do With Old Potting Soil To Get The Most Out Of It

What to do with old potting soil is a common question. Don’t throw it away! Here are 6 things to do instead.

Gloved hands holding potting soil
(Image credit: philipimage / Getty Images)

Potting soil plays a central role in backyard gardening during the summer months. That’s when gardeners are installing new beds, refreshing old beds, and planting seeds and starts. Roll around to the end of August and the growing season is coming to an end, sometimes before the bags of potting soil are used up. And then there’s the potting soil used to grow annuals that have germinated, flowered, and died.

So, what to do with old potting soil? If you are wondering what to do with old soil, read on. We have a lot of good ideas for you.

Do You Throw Away Old Potting Soil?

The throw-away culture of yesteryear is now considered wasteful. Our nation has become more conscious of waste. As recycling came into its own, disposable straws disappeared from the coffee shops and one-use bags were banned from grocery stores. That new awareness means that tossing out old potting soil just isn’t an acceptable option.

Yet you have to do something with old potting soil. Do you find yourself asking “Where can I dump old potting soil?” Or, “Can I put old potting soil on my lawn?” You definitely can recycle that potting soil yourself in your very own garden.

What to Do With Old Potting Soil

Potting soil doesn’t “go bad” after one use. That means that you can treat unused half-bags of potting soil in exactly the same manner as potting soil that was to grow pots of annuals or vegetables during spring and/or summer. Just be sure not to reuse soil that was used to grow potted plants that died from bacterial, fungal or viral disease.

Assuming that isn’t the case, you have options! Here are six great ones to consider.

  1. Landscape hole filler or topper for current beds - Use old potting soil in the landscape to fill any holes on footpaths. It can also be used to top off existing flower and vegetable garden beds. The soil acts as a sort of mulch to protect the old beds from temperature swings. Don’t use soil from potted plants that died from disease, however, without sterilizing it.
  2. Starter soil for new beds - Are you installing new beds in your garden that will be used in spring for flowers or crops? Old potting soil makes a great base soil. In the spring, you will top it with new soil and add appropriate fertilizer.
  3. Compost heap - Here is the easiest option of all: Simply toss the old soil or unused half-bags of soil right on the compost bin. A good compost pile should be a balanced mix of green material, brown material and soil. As you blend in green and brown materials, the old potting soil will be incorporated into the compost to be used for future plantings.
  4. Layered on lawn - Lawns need love in winter too. Why not spread a thin layer of the old potting soil on top of that lawn. Over time it will work its way into the soil, and, in the meanwhile, it will offer some winter protection.
  5. Reuse in potted plants - Out with the old, in with the new! That attitude was typical for in years gone by when it came to old potting soil, but it isn’t the rule anymore. It is entirely possible to reuse soil recovered from container planting as long as you blend in about ⅓ new potting soil and add fertilizer for nutrients.
  6. Make a potato bin - What is a potato bin? It’s a home-made container made of box-wire frame and up to 4 feet (1.2 m) tall in which potatoes will be grown. Start this project in the fall by layering newspaper in the bottom of the bin, then add used potting soil, shredded fall leaves, aged horse manure and compost. Let this sit all winter long and toss in seed potatoes in spring.

Frequently Asked Questions

Do I Have to Replace Potting Soil Every Year?

When you use potting soil for container plantings, it’s not a good idea to leave the same soil in the pot for next year’s plants. That is because the nutrients in the soil have mostly been depleted by that year’s growth. In addition, some used potting soil may contain pathogens.

Can I Put Old Potting Soil in My Garden?

Yes, you can use old potting soil in your garden beds. It’s possible to use it to start new beds, layer it on the lawn, use it to top the soil in current beds, or even make a potato bin.

Teo Spengler
Writer

Teo Spengler has been gardening for 30 years. She is a docent at the San Francisco Botanical Garden. Her passion is trees, 250 of which she has planted on her land in France.