How to Refresh Old Potting Soil and Save Money

By: Angela Judd | August 30, 2024

Can you reuse old potting soil? At the end of the growing season, the soil in containers can become compacted, depleted of nutrients, and less effective at supporting plant growth. Starting with fresh potting soil each time you plant is ideal, but it can be expensive. Follow these steps to refresh your old potting soil, use it for another season, and save money.

IMPORTANT NOTE: If the plant in the container struggled with pests or disease, it’s best to dispose of the soil, clean out the container, and begin with fresh potting soil.

1. Empty Old Potting Soil Onto a Tarp or Wheelbarrow

The first step in refreshing old potting soil is to dump out the existing contents of the container onto the tarp or into a wheelbarrow.

Once the soil is out, it’s a good time to clean the inside of the container with a stiff brush and ensure the drainage holes are not blocked. Rinse it well and let it dry in the sun. Also, scrub off any ollas. Clean ollas will wick water more efficiently.

2. Remove Old Plant Material

Removing old plant material is the next step in reinvigorating old container soil. This includes pulling out spent plants, roots, and any debris left in the soil.

NOTE: If there isn’t much soil left after the plant material is gone, it may be best to start over with high-quality potting soil.

3. Loosen and Water the Soil

Over time, container soil can become compacted, making it harder for roots to grow and for the soil to hold water and nutrients. Compacted soil can also turn hydrophobic, repelling moisture instead of absorbing it. To fix this, gently break up the soil with a hand trowel or garden fork. Aerating the soil improves its structure, making it easier for roots to spread and water to absorb and drain properly. Finally, water the soil thoroughly, giving it time to hydrate fully.

4. Mix in Fresh Worm Castings to Refresh Old Potting Soil

After cleaning out and loosening the soil, it’s time to mix in fresh worm castings. I use in-bed vermicomposting bins, and the harvested castings are free! Worm castings, in particular, are an excellent way to refresh old potting soil. They are rich in nutrients and beneficial microbes that help improve soil health and support plant growth. Learn more about the benefits of worm castings in this blog post. The ideal amount is about 5% worm castings in the soil. You can also add some fresh compost to the spent potting soil.

5. Incorporate Organic Fertilizers to Refresh Old Potting Soil

Add some balanced organic fertilizer to refresh your old potting soil. Used container soil is often devoid of nutrients because they are rinsed out of the soil each time you water. This is the one I like to use, but any balanced organic fertilizer will work. Use the least expensive one you can find. The back of the package should tell you the correct amount to add to your soil.

6. Add New Potting Mix

The final step to refresh old potting soil is to mix in some fresh potting mix. I like to add an equal amount of fresh soil to the old soil. This helps ensure plenty of perlite, coconut coir, or other moisture-holding ingredients essential for container gardening soil. I use the Raised Bed Mix from Arizona Worm Farm in all my raised beds and containers. Learn more in this blog post.

7. Fill Containers Back Up

Add the refreshed potting soil to the clean container. Fill the container all the way up with soil. Don’t add fillers like rocks. Containers naturally limit the size of roots, so giving plants access to as much soil as possible is essential.