Reusing containers and pots for planting this year’s garden is a great way to minimize waste and save a little money, but it’s not a requirement. In fact, mixing fresh organic soil with last season’s organic soil left in the container can actually help revitalize the soil!
However, there are many gardeners who believe thoroughly cleaning and sterilizing your containers each season and starting with fresh organic soil is the best way to eliminate any risk of harmful pests or fungi that may have over-wintered in your containers. Below are the best steps to incorporate in your spring gardening routine for container gardening.
Why it’s good practice to thoroughly clean containers
Many plant diseases and pests can overwinter in the small amount of soil that might be stuck to your container. Some can leave survival structures and spores right on the surface. While you would surely notice a vole or shrew hiding in the bottom of your pot, other issues like harmful fungi, bacteria, or eggs aren’t so easy to spot.
The risks of not sanitizing containers before reusing
Soil-borne pests can rise again, coming out of dormancy to infect your new plants and cause trouble. Insects, fungi, and other plant parasites may wait in debris stuck on your pots. Pythium is a common plant pest that causes root rot. Rhizoctonia is a genus of fungi that can cause root rot, damping off, and leaf blights.
Cleaning Solution Recommendations
You won’t need any complex chemicals to get the job done. Household bleach is one of the easiest, least expensive, and most effective ways to sanitize your reused potting containers. Regular liquid dish soap helps to loosen stuck deposits and dissolve salts and residues.
Other household cleaners can also be effective if you have only a few pots to clean. Common household general purpose cleaner sprays like you would use on your counter or bathroom may work fine, but bleach is the standard method.
Alcohol solutions like rubbing alcohol are excellent for sterilizing pruning tools between plant tasks, but the volume needed for sanitizing pots isn’t practical.
Considerations for different materials: terracotta vs. plastic
Plastic pots and glazed pottery containers are non-porous. In contrast, terra cotta and clay containers are porous, meaning they aren’t impervious to soaking up water. Terra cotta pots will benefit from a longer soak time, however, a diluted household bleach solution will work for both.
Steps to Properly Clean and Reuse Garden Containers
You can do it all in the kitchen sink or bathtub if you only have a few small containers. If you need to sanitize larger pots or have many containers to do, you should set up to perform this potentially messy operation outside. Wear clothes you don’t mind getting wet and dirty.
- Assemble your gear. Depending on your pot types, you may need a tub, sponges, dishcloths, a nylon brush or scrubby pad, an old toothbrush, gloves, a wire brush, and bleach.
- Remove all old plant residues, stuck on soil, and mineral deposits. You might need the scrubby pad for this on the plastic pots. The toothbrush works great on seed trays. Terra cotta can handle the wire brush if needed. Give the containers a vigorous scrub with warm water and dish detergent to remove all soil, mineral, salt deposits, and other matter. When you are done, the pots should look clean — nothing is left inside.
- Prepare a 10% bleach soaking solution by mixing 9 parts water with 1 part bleach. Watch out for the fumes. Pouring a lot of bleach can be hazardous. Follow any safety precautions on the label. Doing this step outside also helps with that strong, irritating bleach odor. To make the bleach solution, dilute 1 cup of bleach in 9 cups of water. Scale up as needed for larger quantities. For example, if you need about three gallons of solution, that would be 12 quarts total, so you’d need about 1 ¼ quarts of bleach and 10 ¾ quarts of water.
- Soak pots in the bleach solution for at least ten minutes, but 30 minutes is better. Swish and shake the pots in the solution to dislodge any air bubbles hiding in crevices. Air bubbles will prevent the bleach solution from sanitizing the entire surface.
- Ensure no part of the pots are left above the bleach solution. Use a heavy screen and a weight to hold plastic pots down (they float).
- After soaking, remove from the solution and rinse thoroughly with clean water, then allow to air dry.
- Keep sanitized, ready-to-use containers away from uncleaned ones. Don’t restack them with dirty ones and make more work for yourself!
You don’t have to do this if you feel confident you are not at risk for soil-borne pests and pathogens. But if you do, following these steps will protect the investment in time and dollars you have with your container garden! Once you’ve done it, you’ll find that sanitizing all of your pots at once isn’t that big of a chore, and it will become just another spring routine.
Sanitizing your reused pots and containers ensures you are giving those young plants the best possible start and can prevent costly losses.
Remember to use new potting mix. Don’t go to all that work just to reuse possibly contaminated potting media from last year!
About the Author:
Andy Wilcox is a freelance writer and flower farmer who is passionate about gardening, horticulture, and forestry and believes healthy soil leads to healthy people. He is a Master Gardener and a member of the Farmer Veteran Coalition of Wisconsin. He can be reached via email: email@example.com.