Clean Makes Green

Seedstarting Containers


Clay pots, transplant flats, seed trays, etc. These are just some of the many devices we use to start our seeds. And most of the time, they work just fine. But occasionally the seeds we plant will start sprouting and looking healthy. Then, for no apparent reason, they will die off.

What happened? Disease. Certain spores, fungi, and bacteria can infect seedlings and weaken and/or kill them. These organisms may be present in the pots and seed trays that you re-use. Many of these can survive quite nicely in a dormant state. Then when soil is added and seeds planted, the organisms “wake up” and begin feeding on your tender young seedlings?

What can we do about it? The answer is simple. Clean and sterilize your containers. The Philadelphia County Master Gardeners recommend the following procedure for effectively cleaning and sterilizing your containers:


  • Soak pots and other planting containers in warm, soapy water to loosen fragments of matter. Use a scrub brush to scour the pots clean, scrubbing off any debris as well as mineral/salt deposits.
  • Use steel wool for difficult to remove stains, and rinse with warm water until all the soap runs off.
  • Make a bleach solution: 1 part bleach to 9 parts water. This is equivalent to 1.5 cups of regular strength bleach and 13.5 cups of water. (Our note: if you are using concentrated bleach, use 1 cup of bleach to 14 cups of water.)
  • Completely submerge pots and planting containers in the solution and soak for 10 to 15 minutes.
  • Completely submerge pots and planting containers in the solution and soak for 10 to 15 minutes.
  • Upon removing the containers, rinse with warm water.
  • Scrub lightly with soapy water (using unscented dish soap) and rinse well until soap runs off and water runs clear. Inspect for remaining residue and repeat the procedure if necessary. (If stains or residue remain after the sanitation process, do not reuse the pot.)
  • Lay containers out to dry for 24 hours before using. If possible, dry pots in direct sunlight for some of that time. Exposure to the sun can help to kill off certain bacteria.


Thoroughly washing and disinfecting your containers will greatly reduce the odds that your seedlings will be weakened or killed by a disease causing organism. And although it seems like a lot of unnecessary work, the healthy seedlings you germinate and transplant will make your efforts well worth it.

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