IF YOU WANT to reuse your clay pots, it is important to clean, sterilize and remove fertilizer and hard-water salts from them prior to reuse. It is a chore that can quickly become unmanageable unless you clean your used pots daily while you are repotting during the marathon repotting season in the spring.
SCRUB DEBRIS FROM THE POT The first step is to remove any potting mix, roots and other detritus from the pot. I fill a 5-gallon (about 19-L) bucket with water and drop the pots into the bucket as I am repotting. You can add a little dishwashing liquid to the water if you like. Your last repotting chore of the day will be scrubbing these pots. Use an abrasive pad to scrub away as much of the adhering roots, encrusted salt and other debris as you can.
STERILIZE THE POT Sterilizing porous clay pots is necessary to avoid transferring pests, diseases or viruses from the last occupant to the next occupant of the pot. You can use either chemicals or heat to sterilize clay pots. Traditional Bleach Soak.
[1] Clay pots are porous so they can absorb salts and pathogens which can be damaging to the next occupant of the pot. Pots should be cleaned and then sterilized before they are used again. Your final repotting chore of the day is cleaning the debris from the pots so you do not end up with the tedious chore of cleaning a stockpile of dirty pots.
The traditional advice is to disinfect your clay pots by soaking them for several hours in a 10 percent (by volume) bleach solution (one part chlorine bleach to nine parts of water). If you are using a 5-gallon (19-L) bucket, add ½ gallon (1.9 L) bleach, drop in your scrubbed pots and fill to the top with water. You can also add pool algaecide (2 tsp/gal [about 10 ml/3.875 L] if 10 percent strength) in lieu of, or in addition to, your bleach solution for extra killing power. You’ll pull the pots out of the bucket, wash them off with a hose and drop them into a second 5-gallon (19-L) bucket filled with water. Let them soak for several hours to remove any residual bleach or algaecide. Remember to use rubber gloves so your skin doesn’t contact the bleach or algaecide solution which, after a very few exposures, can cause skin sensitivity and chemical burns. The bleach or algaecide kills everything with the possible exception of viruses so the next step is heat treatment. If you bake the pots in the oven at 400 F (260C) for two hours, any virus will be eliminated. Add your used rhizome clips and other wire products to the oven to decontaminate them at the same time. Let the pots cool off in the oven and they are ready to be reused, assuming the salts are gone. Dishwasher and Oven Alternative.
[2] Once you have removed the debris from the pot, you can use a dishwasher to finish cleaning them and help draw salts from the pot. The pots still require sterilization to eliminate virus particles.
I have started washing prescrubbed pots in the dishwasher, followed by baking them in the oven, thereby eliminating the need for the bleach soak. After the initial scrub, I let the potssoak in a water-filled 5- gallon (19-L) bucket to start dissolving any residual salts. Alternatively, you can bring them into the kitchen and soak them in hot water, which will hasten salt dissolution. I scrub the pots a second time to remove encrusted salts and residual debris and then pop them into the dishwasher, sometimes with twice the normal amount of detergent or a few teaspoons of trisodium phosphate. The heat and detergent will draw the salts either out of the pot or to the outside edge of the pot. As they are removed from the dishwasher, check for any remaining salt encrustation and, if present, scrub with an abrasive pad while the pots are still warm. Then bake the pots in the oven for two hours at 400 F (204 C) along with any wire products that need decontamination. Let them cool in the oven. If salts are not visible on the pots, they are ready to be reused.
REMOVE STUBBORN SALT ENCRUSTATION Sometimes you will find or acquire pots with stubborn salt encrustations that are still present after your normal cleaning sequence. You need to remove any residual salts that have been absorbed into the porous clay pots. Otherwise, the roots of your newly repotted orchid can burn if they come into contact with the white deposits as a result of salt toxicity. If soaking and washing the pots does not remove all the salts, you have a few alternatives.
[3] Terry set up a heat treatment station in our boat house with a secondhand oven he bought for $50. I set the oven to 500 F (260 C) and let the pots bake for two hours to eliminate all pathogens and also to help remove stubborn salt encrustations.
Mild Acid Soak
If the pots still have visible white stains, try an overnight soak in a mild acid. Use white vinegar in whatever concentration you are comfortable handling, either a pure or diluted solution. Scrub any residual salt from the pot, and follow with a second soak in water to remove the acetic acid. Ray Barkalow of First Rayssuggests using citric acid, a mild organic acid that is very effective for removing deposits. Citric acid may be sold in your grocery store for use in ethnic recipes as “sour salt.” Even at 1 cup/gallon (¼ L/3.875 L), it is still quite plant-friendly, so you need not worry too much about rinsing. The product is used in fertilizers to enhance solubility and in leaf cleaners for removing deposits.
Simmer on the Stove
For stubborn salt deposits, drop your pots in a stew pot filled to the brim with water and set on a slow simmer for several hours. The heat will help draw the salts from the pot.You can add a mild acid such as vinegar or citric acid to help solubilize the salts. Then soak the pots in fresh water to remove leftover acid.
Simmer on the Stove
For stubborn salt deposits, drop your pots in a stew pot filled to the brim with water and set on a slow simmer for several hours. The heat will help draw the salts from the pot.You can add a mild acid such as vinegar or citric acid to help solubilize the salts. Then soak the pots in fresh water to remove leftover acid.
High Temperature
Increasing your oven temperature to 500 F (260 C) during the heat sterilization step will also help remove stubborn salt encrustations. The deposits on the pots are a combination of minerals from the water supply (probably naturally occurring bicarbonates and carbonates), minerals from the fertilizers (nitrates and sulfates predominantly) and organic plant wastes. Ray Barkalow of First Rays contends that these materials are all blended together and are probably deposited on the pot rather than chemically bonded to it. The cooking process destroys the sticky organic materials and possibly changes the physical or chemical properties of the inorganic materials, making them more friable and easy to remove. At any rate, cook the pots for an hour or two at your oven’s highest temperature setting and when the pots are cool enough, place them in the sink and fill the sink with water for a brief soak. It is best to use this alternative when the house can be opened for ventilation and vapors can be dispersed easily. The fumes are similar to those you get when you put the oven through a selfcleaning cycle. You will have to ventilate to get rid the house of fumes, but your pots will look brand new without using chemicals such as bleach or acid.
[4] Pots in the final soak after heat treatment. The pots look almost brand new and are ready to return to duty.
ONE-STEP CLEANUP USING A KILN Bob Scully,Jr., of the former great orchid nursery Jones & Scully, uses a kiln to sterilize and desalt pots prior to reuse. He simply removes the coarse debris from the pots and runs them through a kiln. The kiln has a firing temperature on the order of 1,000 F (540 C), a high enough temperature that pests, diseases, viruses and salts are all eliminated in one step. He brushes any residual ash off the pots after removal from the kiln and they’re ready to reuse.
Cleaning up your pots can quickly become a chore if you stockpile dirty pots to handle “later.” Drop your dirty pots in a bucket of water as you are repotting so the debris and roots will be softened up by the end of the day. Your last repotting chore of the day will be to scrub the debris from the pots. Then you either stockpile prescrubbed pots or continue on with the sterilization process and drop them into a bleach solution, wash in the dishwasher, cook in the oven or do whatever you choose to sterilize your pots. You will be able to sleep the sleep of the righteous knowing that your “almost new” pots are ready for your new beauties.
— Sue Bottom started growing orchids in Houston in the mid-1990s after her husband Terry built her first greenhouse. They settled into St. Augustine, Florida, Sue with her orchids and Terry with his camera and are active in the St. Augustine Orchid Society, maintaining the society’s website and publishing its monthly newsletter. Sue is also a member of the AOS Editorial Board (sbottom15@hotmail.com).
