Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
At the end of the summer, it’s not enough to just remove the dead plants from your containers. You should also remove the potting soil and clean and sterilize your containers before using them again in the spring.
Can Potting Soil be Re-used?
Potting soil should never be reused. It has been sitting outside all summer collecting weed seeds, insect eggs, fungi and mold spores, all of which can overwhelm and even kill anything planted in it the following year. You should discard your used potting soil in the fall.
There are articles on the internet with instructions on how to sterilize your used potting soil in your oven or your microwave. Ignore them. Heat may not kill everything and the heat may not be evenly distributed throughout your soil. Some gardeners throw their potting soil into their gardens. This is also not a good idea. You are adding weed seeds, insects, fungi and mold to your garden which will grow next year in your garden.
Potting soil is expensive. No one likes to just throw it out. I add it to my composter. A properly constructed compost can reach a temperature of 120⁰F. This will be sufficient to kill all of the weed seeds and pathogens in your potting soil because the soil will be heated for months during the winter instead of just an hour or less in your oven or microwave. The microbes that break down your compost ingredients will also destroy the fungi and mold spores. The added benefit is the resulting nutrient rich, organic compost that can be safely used in your garden as a mulch or fertilizer or even as potting soil in next year’s containers.
How to Clean and Sterilize Your Containers
Bleach Your Containers
After removing the soil from your containers and brushing out any that is stuck to the sides or bottom, you should sterilize your pots to kill any bacteria or mold that may be clinging to the sides. Use a solution of 1 part household bleach to 9 parts water. Mix your solution in a sink or bucket that is large enough to hold the pot that you are sterilizing. You want to completely immerse the container in the solution for a minimum of 10 minutes. Then rinse thoroughly.
Get Rid of Salt Deposits
After you have sterilized your container, you should get rid of the mineral deposits and salts that have accumulated over the growing season. These deposits leached out from the water and fertilizer that kept your plants healthy during the growing season. Left to accumulate in the container, they can damage or kill your new plants the following year.
Use a wire brush or steel wool to remove the deposits from your clay pots. For plastic pots, a plastic scouring pad should be sufficient. Stubborn deposits can be scraped off both clay and plastic pots with a knife.
Wash Your Containers and Dry Them in the Sun
The final step in preparing your containers for reuse is to wash them in soapy water and rinse thoroughly. You want not just to get them clean but also to remove any bleach residue. Bleach kills plants as well as fungi and mold so you want your containers to be completely free of bleach before putting plants in them again. Leave your pots in the sun for a few hours to dry. This takes advantage of the sterilizing effect of the naturally occurring ultra violet radiation in sunlight.
How to Properly Store Your Containers
You should store your containers in a protected area if possible. Your basement, garage or garden shed are all good places to store your containers over the winter. Leaving them outside, exposed to the elements, will weather them. They won’t be as attractive and won’t last as many years as they would have if you had stored them indoors.
Plastic pots can be stacked, but it is recommended that clay pots be stored individually. They are fragile and the weight of stacked pots could crack or even break the pots on the bottom of the stack. If you are storing your pots in an unheated shed, make sure that you clay pots are completely dry before you place them there. Any moisture left in your clay pots will expand and contract with the varying winter temperatures creating cracks or breaking your pots.
Reusing your containers every year benefits both the environment by reducing your carbon footprint and your budget by eliminating the need to purchase new containers every spring. To ensure healthy plants in your containers, clean and sterilize your containers at the end of each growing season and use new potting soil in the spring.
© 2013 Caren White
Lisa Bean from Virginia on December 12, 2018:
This is great info. I'm so bad about cleaning out pots after use - most of the time I will clean them in the spring time or when I'm ready to plant something else in them...
Caren White (author) on October 25, 2014:
Faith, cleaning pots is no fun, but in the spring I'm always glad that I did. Thank you so much for the vote, tweet and pin!
Faith Reaper from southern USA on October 25, 2014:
Great information you have shared here! I had no clue that the pots even needed cleaning ... so thank you for that, and it makes a lot of sense after reading your insightful hub here.
Voted up ++ tweeting and pinning
Caren White (author) on August 23, 2014:
Glad it was helpful, Peg. Thanks for reading and commenting.
Peg Cole from North Dallas, Texas on August 23, 2014:
This is good information to put to use as summer winds down. I hadn't thought to add the potting soil to my compost bin, so that's a really useful tip. Thanks.
Caren White (author) on November 07, 2013:
I am a compost fanatic, always looking for new "ingredients"! Thanks for reading and commenting Jackie.
Jackie Lynnley from the beautiful south on November 07, 2013:
What a great idea, I am just starting a compost pile having 3 hens and stray and read that could make a killer fertilizer in about three month so I will throw all my potting soil on it, thanks!
Caren White (author) on October 31, 2013:
Ginger, so glad you found it useful. I'm looking forward to spring too!
ExpectGreatThings from Illinois on October 30, 2013:
I didn't know half of these tips. I have always just dumped the soil in my beds. No wonder I have so many weeds every year! Pinned this so I can refer to it in the Spring. And oh, I can't wait for Spring! - Ginger
Caren White (author) on October 30, 2013:
Flourish, it takes a little effort but it is so worth it.
Pearl, a composter is so versatile. I love being able to make something useful (compost) out of garbage.
Connie Smith from Southern Tier New York State on October 30, 2013:
This is great information! From now on my old potting soil will go in the composter, and I will be more diligent about cleaning and sterilizing my pots. Thanks for sharing ;) Pearl
FlourishAnyway from USA on October 30, 2013:
I had no idea pots need to be cleaned like this, but it makes sense. Glad you provided insight in this article. Thanks for doing so.