What to Do With Old Potting Soil
(the Dirt From Your Pots)

by | Updated: May 27, 2021

What to do with old potting soil - one option is composting

What can you do with the dirt in your pots after your flowers have died?

You have a few options for what to do with old potting soil!

Let’s assume, for a sec, that your flowers were healthy at the end of the season.

If yes…

Here are 4 things to do with old potting soil:

1) You can put the soil in a sealable container. Store it for next season.

Where to store used potting soil - old garbage cans work well for the dirt

An old garbage can works well because the lid creates a good seal and the wheels make it easier to move.

But any type of storage container that you can seal should work.

The nutritional value is gone from the soil, so you wouldn’t want to use it on its own next season. But it’s possible to thoroughly mix it with fresh ingredients — like new potting soil or “compost.” (Compost is a mix of organic materials used to improve soil.)

This approach allows you to re-use some of your old potting soil.

You may want to put your storage container in the sun and put a little water in it, so it can heat up. You’re trying to “cook” any bad stuff that may be hanging out in the soil — like insect eggs or disease. (Insects can overwinter and/or lay their eggs in the soil.)

When I lifted the lid on the garbage can pictured above, whew! I could feel the heat coming out. This is a good thing.

2) You may be able to take used potting soil to a yard waste drop-off program.

Many cities offer “leaf and yard waste drop-off” programs in the fall. They’re a great way to dispose of the materials from your flowerpots, like your dead flowers and old soils. And the materials you drop off will be used to create compost, which is good for our soils and plants.

The companies that do commercial composting have machines that can heat the soil and leaf material to very hot temperatures, so the compost can be safely used next year.

Leaf and yard waste drop-off

To see if your city offers this type of program:

  • Look on your city’s website OR check nearby cities. Some cities only make these programs available to their own residents. But other towns make their leaf and yard-waste drop off services available to anyone.
  • Search for words like, “Leaf drop-off,” or, “Yard-waste drop-off.” Often times, these programs aren’t advertised as composting programs.
  • Read up on what’s allowed for yard waste. Dead flowers are usually allowed, but make sure they’ll take your used potting soil too. I usually take the potting soil with me and ask when I get there. (I’ve never had an issue, but I imagine it can vary by city.)
  • Follow the instructions for the drop-off. For example, you may be asked to put your yard waste in brown composting bags. They look like tall paper bags. The instructions should tell you where to find composting bags, like a local hardware store. Or, the instructions may say you can bring your yard waste in any type of container. They’re just going to have you dump it out — as was the case in the photo above.

3) You can add the old soil (and flowers) to your own compost pile.

Home composting is a topic for another time. But just know it’s another thing you can do!

Dirt and flowers in a compost bin

4) You can mix old potting soil into your flower garden beds or spread it lightly across the top.

The dirt from your flowerpots isn’t adding anything beneficial from a nutritional perspective. Over the summer, all the good stuff left the soil with each watering.

But we have such tricky soils in the Rocky Mountain region — like clay and sand. The potting soil may help improve the texture of your soil in the ground. That can lead to better water drainage for your plants, so they have happier roots.

And hey, it beats putting the soil in a landfill.

Here are a few tips:

  • It’s easiest to mix old potting soil into the ground in areas that don’t have plants.
  • If you’re spreading a thin layer of potting soil on top of the ground near plants, lightly spread it in the areas between plants, but keep it away from the “crowns” of your plants. (The crown is where a plant’s stem comes up from the ground. It’s where the stem and roots connect to each other.)
  • If you’re going to mix the old soil into the ground near existing plants (like “perennials” — the plants that return each year), be careful where you dig. You don’t want to disturb their roots.

Now, what if your flowers had disease issues?

Then, put ALL the contents from that flowerpot in the trash — including the potting soil.

Disease can carry over from one year to the next in both the soil AND on the flowerpots themselves.

If you had diseased plants, it’s a good idea to sterilize your flowerpots, so you can keep next season’s flowers from getting sick. You can find out how to sterilize your flowerpots here.

If there were any disease or insect-related issues in your flowerpots, there’s a chance you may accidentally spread these issues to next season’s flowers. That’s what we’re trying to prevent.

“Can I leave the dirt in my flowerpots until spring?”

Yes, but there are advantages to emptying your pots in the fall:

  1. You can participate in yard-waste drop off programs in the fall, as we’ve chatted about above.
  2. You’ll have less work in the spring and can focus your energy on planting.
  3. You’ll lower the chances of your pots breaking over the winter. If your potting soil has moisture in it and it freezes in your pots over the winter, it can expand and damage your pots. You can learn more about flowerpot freeze damage in: “When should I empty my flowerpots?”
  4. You don’t have to worry about insects laying their eggs or overwintering in your flowerpots.

Thanks for thinking about how to re-use potting soil

More than 50% of Denver’s landfill waste comes from people throwing out organic materials, according to the City of Denver.

Cheers to you for exploring what to do with old potting soil and finding ways to use it in a productive way!

Related tips that may interest you:

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I’m a Certified Colorado Gardener, dog mama and Midwesterner-turned-Colorado girl. I help budding gardeners in the inter-mountain west get more confident with flower gardening, so you can create an outdoor space you love. More about Ann >>

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