Cleaning Seed Starting Supplies & Pots....Without Bleach!

Over the years, I've used a couple of different methods to clean my seed starting supplies and pots.  Way back in the beginning of my gardening journey many years ago, I simply rinsed everything off in the laundry room, let it dry, then put it away.  Then one year, I was hit hard with Damping Off - the two words that strike fear in the heart of all seed starters.  Damping off is a fungus that attacks fragile seedlings shortly after they emerge from the soil.  One day your seedling is fine, then the next, it's keeled over and limp as a noodle.  If you look closely, you'll notice that the bottom of the seedling (just above the soil line) looks pinched.  Unfortunately, once your seedling is attacked, there's nothing you can do to save it - you have to start over.

I lost a good chunk of my seedlings that year and, after a bit of research, I started to sterilize all of my equipment using a 10% bleach solution at the end of the season.  It was effective but it was also a long, tedious process. Should you be interested in giving this method a go, I've provided a detailed description at the end of this post.  In a nutshell, you rinse everything off followed by a 20 minute soak in a bleach solution, then rinse again & let dry.  This cleaning process would usually extend over a couple of days, especially once my seed starting obsession grew, as you can only fit so many trays/pots/cell packs into the bleach solution at one time.

Then one year I read about the sanitizing power of the sun, not in relation to cleaning pots but in general.  That got me thinking - why couldn't I use this power to simplify this grueling task?  So I tried it out's been years since I broke out the bleach and so far so good (knock on wood!!)

My New 'No Bleach' Method

My new simplified method of cleaning up is SO much easier and, so far, it's proven to be effective.

Firstly, you need to pick the right day to do your cleaning, which basically depends on the weather.  It should be hot (mid-20's Celsius/mid-70's Fahrenheit or higher), sunny and relatively calm - you don't want your supplies blowing all over your yard!

Now to the actual cleaning - you only need two tools:  (1) A hose with a strong nozzle (my favourite is this one from Dramm) - I use the 'Jet' setting for a nice, strong spray (2) A small scrub brush to get at any stubborn soil - nothing fancy needed here...mine is from the dollar store.  And that's it.

The actual cleaning involves:

(1) Using the sprayer to blast all of the soil from the pot/tray.

Using a powerful sprayer does most of the work for you

(2) Setting the pot/tray in the sun to dry.  I make sure to place all of the pots upright to let in as much sun/airflow as possible, then after a couple of hours I'll flip them over so that the undersides are exposed & allowed to dry as well.

If I have tall/narrow pots that tend to tip over, I'll place those in a mesh tray so that they stay upright.

These narrow pots would fall over if they weren't in a tray

While the sun may not 'sterilize' my pots, the shot of UV and heat 'sanitizes' them enough where I've not had any issues with damping off for the past several years.  

This method saves me time, it's easy to do, it's a lot less hassle AND I avoiding the decidedly unpleasant aspect of both dealing with and then disposing of the bleachy water.

A batch of pots and trays drying in the sun

Handling a bleach solution more than once per year doesn't do you or the environment any favors so in the past, I would wait until the very end of the season to clean up...which brings me to another big benefit of the Sunlight method:  I can do my cleanup in smaller batches throughout the summer instead of having one ginormous pile to deal with in September.

At the end of the day, the question that you may be left with is this:  Is there a greater risk when you use the Sunshine vs Bleach method?  I don't have a definitive answer so I'll go with maybe (I would love to see a study on this!).  However, I'll stick my neck out and say that, based on having successfully used this method for years now, the risk is fairly small.  So for me, the hours of work and hassle it saves/has saved over the years is worth the possible slight increase in risk.

Remember too that simply using bleach to sterilize doesn't guarantee you won't be hit with damping off as the fungus can come into your home unsuspectingly on soil you purchase or even on your hands from handling other plants or tools.  So regardless if I use bleach to clean my pots or not, I always up my defenses when it comes to certain plants that are more susceptible to damping off (such as brassicas) by sprinkling the soil with a bit of cinnamon and topping it off with vermiculite when I sow the seeds.

I do have one caveat to my no-bleach method:  If I do end up having an outbreak of damping off at some point, I'll most likely use bleach that year.  Not using bleach in this situation would increase the risk of contamination the following year beyond the point that I'm comfortable with.


If you have an alternative method of cleaning/disinfecting your seed starting supplies or would simply like to share how you do one of the most tedious tasks of the season, do let me know in the comments!

Using Bleach to Clean Pots, Trays, Cell-Packs

Note that you should not use bleach on any supplies that are made of metal or have metal parts such as pruners, trowels, etc. as bleach is corrosive and will cause irreversible damage.  If you need to disinfect these types of tools, first wash them as usual with water and/or soap, then spray them with isopropyl alcohol or a disinfecting spray like Lysol.

  1. Sweep/clean the area (in my case I used the garage floor) so that you have somewhere to place the cleaned pots, cell packs, etc. once they are washed.  Remember you are using bleach so you want to stay away from grass or garden beds - stick to doing this on a driveway or in your garage.
  2. Fill a large vessel (big enough to hold your largest pot/tray - I used a plastic garbage can) with water and add enough bleach to make a 10% bleach solution.  IMPORTANT:  Please wear long rubber gloves & goggles when you are handling bleach, either directly (i.e. when pouring) or indirectly (i.e. when submerging pots).  It is corrosive and you could get chemical burns (yet another reason I avoid using bleach if at all possible!)
  3. Before placing your pots in the bleach solution, rinse them off so that they are relatively free of any soil.
  4. Add your pots and other plastic/terra cotta/ceramic supplies to the bleach solution, making sure they are completely submerged.
  5. Allow the items to sit in the bleach for about 20 minutes or so.
  6. Remove each item from the bleach, then rinse it thoroughly with clean water.  You can either have a 2nd container with clean water (disinfect the 2nd container with bleach first, then rinse it out and fill with clean water) or do as I did - simply rinse each item off thoroughly with a hose sprayer.
  7. Place the freshly clean pots, cell packs, etc, on a clean surface to dry in a single layer.  Stacking things will just delay the drying process.  I would simply lay everything out on the garage floor (see #1).  Drying usually takes a day or so, depending on the ambient temperature - when I left this task to the end of the season when the temps were a lot cooler, it would often take a couple of days for everything to thoroughly dry.   Also, you may have to flip things over about halfway through so that the undersides also dry.
  8. Once they are dry, stack them up and put them away...and this was usually accompanied by a big sigh of relief that this task was (finally) done and I wouldn't have to do it again for another 365 days!


  1. Thanks for the tips! I've been sloppy of late in cleaning out my pots but I'm generally using them for cuttings as I generally sow seeds directly in the ground, or not at all ;)

    1. I think that the outdoor environment somehow keeps damping off at bay as I've never heard of outdoor seedings being affected. When it comes to cleaning my outdoor pots for annuals, I'm usually a 'down and dirty' cleaner too (i.e. doing the bare minimum). I've never had an issue so far so I'll likely keep doing that until I do!

  2. Since downsizing and moving I have no room for seed starting, sadly. But I used to do the bleach method which was not a great alternative but what choice do we have sometimes. I love this sunlight method and will keep it in mind if I ever get the chance to seed start again.

    1. Yes - having to use bleach is such a royal pain! Being able to do the cleanup in smaller chunks throughout the season also makes this task so much less tedious :)

  3. I wash my pots and trays throughout the year in batches. I put them in a big trug of water and leave to soak for a few days to loosen the dirt. Then I tackle them with the hose pipe and a little pot brush and leave them out to dry. It's a job I hate doing. I know some people don't wash pots, just leave to dry out then brush the dirt off, but I prefer my way.

    1. I would consider washing out pots important, especially for seed starting supplies as those little seedlings are so fragile. But having said that, I often do things that are 'not what is normally done', simply because I prefer a different way - so long as it works for you, that's what's most important!

  4. WE are lazy gardeners and just brush out our pots and trays, Surprisingle we don't seem to have any problems raising seed. Famous last words!

    1. Ha - with everything you do around the allotment, the last thing I would call you & Martyn is lazy! Fingers crossed your luck continues! :)

  5. This is a great, informative post, Margaret! I don't grow as many plants from seed as you do, but I tend to keep my pots out on the screen porch over the winter. I think it's cold enough (below 0F/-18C some days) to kill the fungi, etc. Then, just before I'm ready to plant, I line up the pots in the sunroom where they bake for a couple of days (actually a similar technique). Happy dreaming of seed starting in 2024!

    1. That's a great process, Beth! Yet another reason for the 'Why we need a Sunroom' list to help nudge my husband in that direction 😉


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