Reusing plastic, clay, and other containers is a great way to save money and reduce the amount of plastic waste that goes into landfills. Plastic containers cannot be recycled in traditional single-stream home recycling programs and, unfortunately, programs to collect and recycle plastic pots are not common.
It is important to clean and disinfect old pots each time you use them whether the pot is plastic, clay, or some other material. Disease-causing fungi and other organisms including insects can remain in old containers and the debris that accumulates in them, infecting the new plants potted in them. Mineral salts can be both unsightly and damaging to plants. The salts leach through clay pots forming a white film on the outside of the pot creating an unsightly container by some gardener's standards. Salts can also accumulate around the rims of both clay and plastic containers. Salt deposits on container rims can dehydrate plant stems resting there.
Proper cleaning and disinfecting of pots requires just a minimum amount of effort, yet can mean the difference between the success or failure of containerized plants. Plus it allows you to reuse containers and reduce plastic waste. Follow the steps below to clean and disinfect used containers.
How to Clean and Disinfect Plant Pots
Both plastic and glazed ceramic pots are non-porous making them relatively easy to clean. Terracotta and clay pots are porous but still possible to clean.
To disinfect the pots, start by using a brush or rag to remove all the loose soil particles. Then wash pots in soapy water (dish detergent works great) and rinse clean. Soak the container in a solution containing one part household bleach to nine parts water for a minimum of 10 minutes and rinse. Prepare the solution by adding bleach to water (not water to bleach to avoid splashing) and protect skin and clothing from the bleach solution. Use the bleach solution within two hours of preparing it.
How to Remove Mineral Deposits from Plant Pots
Mineral deposits can frequently form around the upper inside rim of the pot near the soil line. Remove this mineral deposit from plastic or glazed ceramic pots with a scouring pad. Tough-to-remove deposits can be scraped away with a knife. Smooth any rough edges with steel wool. Rinse the pot and it is ready for reuse.
Both terracotta and clay pots are porous and often mineral deposits are located all over the container. To clean clay pots use steel wool or a wire-bristle brush to remove mineral deposits and other debris. If mineral deposits remain, use a knife to scrape them off. Rinse pots thoroughly and soak them in a bucket of clean water until you are ready to use them. Dry clay pots can wick moisture away from the potting medium dehydrating newly potted plants.
Using Alcohol or TSP (Trisodium Phosphate) Cleaners
Sometimes a soak in 10% bleach for ten minutes is not practical or efficient, such as when you are trying to disinfect just one container. Rubbing alcohol can be used as an alternative disinfectant to 10% bleach. Clean the containers in the same way as described above but instead of soaking them in bleach solution, wipe all surfaces of the container (inside and out) with a cloth soaked in undiluted 70% isopropyl alcohol (rubbing alcohol). Alternatively, the container can be sprayed with rubbing alcohol, provided adequate coverage can be obtained.
TSP cleaners (often sold as deck or siding cleaners) are occasionally used as disinfectants for pruners and other garden equipment but are not practical, economical, and/or safe to use on containers. For this reason, it is not recommended to disinfect plant containers with TSP cleaners.
Using Household Cleaners as Disinfectants
Household disinfectants like surface wipes, cleaners, and sprays (i.e. Lysol, Pin-Sol, Clorox wipes, Microban, etc) are a potential alternative to a 10% bleach solution to sanitize containers. These products are generally easier and safer to use than bleach. They are very effective at killing bacteria and other pathogens on surfaces and equipment in hospitals and schools, but their effectiveness at killing plant pathogens on containers and garden equipment has not been well evaluated. It is likely that these products could be effective at disinfecting containers, but a 10% bleach solution is preferred over these products because the formulations and active ingredients of household cleaners can vary by product and their efficacy on containers is not well known.