What I’m about to say goes against traditional wisdom that’s ingrained in nearly every gardener and written about by many a cooperative extension office, but I’m bringing it up to ask a simple question: Why?
Why do we need to wash our dirty pots before germinating seeds or putting plants in them?
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To wash or not to wash
I confess that I haven’t washed my plastic containers in years, at least not in the way that’s usually advised. Consult almost any gardening guide and the instructions often include scrubbing the pots with soapy water and disinfecting them with a diluted bleach solution.
But I, on the other hand… I am firmly in the brush-off-the-dirt, wipe-off-the-gunk camp of annual garden cleanup, and I stack my containers in the potting shed like this, ready for the next round of seedlings. (This is the brush I use, which makes quick work of seasonal clean-up, though any stiff bristle brush will do.)
Occasionally I hose them off to remove any stubborn and particularly crusty bits, or I wash the containers for aesthetic reasons (mostly for gifting plants to friends).
I’ve amassed a towering collection of plastic seed starting pots, gallon pots, six packs, and seed trays over the years that continues to grow, and I can’t imagine hand-washing (or even hand-soaking) every single one of them at the beginning or end of each season.
It seems like a silly waste of effort for not that much benefit, at least where pests and diseases are concerned. (If you’re the type of person who loves to clean, however, then none of this applies to you.)
Why, then, are we told to wash our containers at all?
Do pests and diseases linger on unwashed pots?
One popular argument states that washing pots supposedly reduces the chances of damping off disease.
But researchers now know that to be untrue. The conditions that cause damping off (humidity, excessive moisture, and poor air circulation) originate not from dirty pots, but from poor growing practices like spacing seedlings too close together, overwatering, watering the leaves, and leaving plants in non-ventilated greenhouses or under plastic humidity domes and cloches.
In short, your seedling is more likely to develop damping off because of you rather than a dirty pot.
But can washing pots prevent other fungi, bacteria, or pests from hitching a ride on your new plants? Isn’t washing pots a part of good plant health management?
Maybe, and sure, to a certain extent—but neither reason can justify the colossal pain in the butt of washing a pile of pots in the sink, two or even three times when all is said and done.
While pests and diseases can certainly transfer from an old plant to a new one, the chances of that actually happening are slim.
There may be the rare occasion that a dirty pot harbors root aphids lurking in leftover soil or spider mites hibernating under the rim, or perhaps a plant you tried to grow in the pot was plagued with allium rust or clubroot.
Related: Get Rid of Aphids Naturally With These 9 No-Fail Solutions
If any of that were the case, and serious enough to warrant consideration at all, don’t bother with washing and disinfecting that pot. It’s far more economical to throw it out and use a brand-new pot with brand-new soil instead. The time saved and peace of mind earned is worth the couple extra bucks to replace it.
Read next: Make the Best Seed Starting Mix for Dirt Cheap (It’s Organic Too)
As for terra cotta pots: Salts and other minerals that build up on the outside (usually at the base, and caused by fertilizers or hard water) can be unsightly and can sometimes hinder proper drainage if left to accumulate. Those are about the only reasons you’d need to scrub and wash them with a stiff bristle brush.
Otherwise, the fear of disease running rampant among dirty pots is really, truly overblown.
Should you disinfect plant pots with bleach?
The common advice for disinfecting plant pots is to use a household bleach containing 8.25 percent sodium hypochlorite, and dilute it to a 10 percent bleach solution.
But that dilution amount (8000 ppm, or parts per million, more than even the disinfectant level recommended for hospital settings) is insane. It’s overkill and not something you want to be standing around and inhaling all day.
To put it in perspective, the bleach dilution recommended for cleaning up spills of bodily fluids (like vomit or diarrhea) or disinfecting hospitals with Clodstridium difficile infection is only 5000ppm.
So please, do not disinfect your garden pots with a 10 percent bleach solution.
If you really want to wash your pots at all, hot soapy water is sufficient (and a lot less toxic).
And that brings me to another problem: For the bleach disinfectant to work, you have to wash your pots in hot soapy water first. That means they need to be emptied of all soil and debris, scrubbed with detergent, and rinsed clean. Then you can soak them in a (much milder) bleach solution before laying them out to dry.
You can’t just soak dirty pots in a bleach solution (no matter what dilution it is) and expect them to come out squeaky clean. With the way bleach works, any dirt or organic matter (including soap residue) floating around in the disinfecting solution actually inactivates the microbe-killing power of the sodium hypochlorite.
Bleach also has an expiration date. After a shelf life of six months, it becomes 20 percent less effective with each year that goes by.
Think about it: When was the last time you bought a new bottle of bleach? And how much are you actually disinfecting anything if you’ve been using a bottle that’s been sitting around for more than a year?
Why you should embrace the “dirty” pot
When you think about how plants are grown in their natural environment—outdoors, in the elements, with no coddling from us gardeners—they’re exposed to all the insects and microbes that were there before. Thus, plopping a seed or plant into a dirty pot is no different than plopping it into, well, soil.
How often do you see damping off in your garden? (Not as often as you see it in your indoor seed starting tray, I bet.)
Susceptibility to pest or disease is more an unintended outcome of our own tendencies (to overwater, underwater, sow too soon, sow too late, over-fertilize, or any other simple mistakes), and less a direct result of secondary infection from a dirty pot.
Viable seeds raised under good conditions (where light, moisture, and air circulation are concerned) produce plants that are vigorous enough to withstand your garden-variety microbes (and in fact, they’re made stronger when exposed to these elements because the plants then deploy their natural defense mechanisms).
This is not to to say I advocate poor hygiene or shoddy maintenance when it comes to your tools and equipment. Proper care of pots and other gardening gear goes a long way toward maintaining longevity and sparking joy when you see everything all clean and orderly.
Read more: DIY Tool Cleaning Station: The Fastest Way to Clean Garden Tools
But the advice I constantly read about washing and disinfecting your pots seems like a gardening myth that’s often repeated but lacking in scientific basis.
What are your thoughts? Are you a devoted pot washer, or merely a dirt brusher like me?
This post updated from an article that originally appeared on August 15, 2017.
This is one of the most informative posts I’ve read on this topic. Your clear explanations and real-life examples are incredibly helpful.
I’ll give you one of the best reasons why I washed the pots now or at least wipe them out with rubbing alcohol and let them air dry; SCALE and that awful sticky shiny “honeydew” of excess water and sugars the insects excrete is a suck the life out of your plants. It gets on everything. Especially your hands; my bird of paradise became infested with scale. It was my first time dealing with it. The pot was all sticky. I didn’t know what it was I didn’t even think about it and on my way out of the greenhouse, I picked up an Anthurium and Yep you’re right, you guessed it. Those were beautiful pots and they became completely gross sticky.
And believe me, I’m not as neurotic about sterilizing my tools as I should be, and I work with orchids. But now a good amount of my orchids have scale and sticky pots 🙁
I just had this thought and am curious as to what others might think. I am really anxious to try the not washing out my pots but was wondering if anybody has tried or considered spraying the inside of the pot with neem oil before you put soil in it? I’m thinking if there are any critters in there that the neem oil would take care of that. Would love to hear other people’s thoughts.
This is great advice. I’m bringing in 3 sun-loving plants (lemongrass, hot pepper and a variegated basil) to overwinter in my home and I’ll be using new pots and bagged soil because we had a terrible year with bugs and I don’t want to inadvertently bring any of them (especially the earwigs) inside. I will give the plants themselves as thorough a cleaning as I can & hope they survive the whole process. It’s my first time overwintering anything so it’s an experiment for me as well.
Rowena, I’d love to know how you did with over wintering as I want to try this this season?
Also any tips or don’ts that you may have learnt.
Loulou
I have been of the dirty pot camp. But this year lost over half of my seedlings. I did have them a bit too wet at times I think. The little seedlings seemed quite robust. But then when I transplanted into larger pots, most of them keeled over in a couple days. At that point they had good light, temperature, and air circulation and I used store bought soil. Must have been the injury of transplanting let in the microorganisms that started growing when they were too wet in the flats. But I also switched soils, so hopefully it isn’t that the soil I bought is contaminated. Oh crap I just realized when I repotted I scooped the spilled dirt from the table back in the bag, which undoubtedly included some from the flats. If it wasn’t contaminated it is now. Maybe I can just take whats on top and sterilize it in the oven. Anyway, looks like I’ll have to change camps, especially to clean these pots! If dirty pots means loosing most of my seedlings, I guess at that point it’s worth it to wash em! Tho this old timer I lived with, he used just garden soil mixed with peat for potting, but he would pour a bit of sand on top. I guess the sand would make the surface of the soil dry out fast and reduce the chance of damping off.
Sounds like aphids may have attacked your plants. They’re tiny tiny white bugs you’ll see on leaves, underside of leaves and stems Spray them with Neem oil ( follow directions for diluting and applying)
I hardly ever wash my pots, but when doing so I scrub away any obvious bits. Leave the pot to soak in 3 parts water to 1 parts vinegar solution, for 5 minutes, then scrub with a rag under cold water and leave to air dry.
Just a comment on bleach ratios: 1:32 and 1:9 are commonly used ratios and are actually more dependent on whether the solution is being used in an indoor or outdoor environment than anything else. The hospital ratio would be lower to prevent respiratory irritation from people exposed to the chemicals.
Also note too low OR TOO HIGH a ratio renders bleach ineffective against organisms. When cleaning mound, the solution won’t work at all if there’s too much bleach and not enough water.
I am in your camp on this.
Thank you Daria!
I don’t think I’d even heard about disinfecting pots with bleach! Haha I barely clean mine up at all. I might spray them off with a hose, but that’s about it!
Same!
I’m with you, I just brush out the dirt (and spider webs). I’ve had some issues with seedlings damping off this season, but I think it had more to do with my soil medium and not the pot.
I usually find that damping off issues are a result of too much moisture or not enough air circulation… nothing that a dirty pot can cause or prevent.
Damping off can be controlled by a THIN, SPRINKLE of cinnamon on your potting medium. For lettuce, etc, press a row down, plant the seeds, And Tamp the soil over seeds.
haha Love your blog!
You are so lively!
Amazing job x
-Daria
My pots are lucky if they even get all of the dirt at the bottom dumped out completely! I’m like you, overkill.
Haha, ditto on the dirt still left behind in my pots!
Agree wholeheartedly. Of course, if you’ve had a fungal attack of some kind, or have collected pots from unknown source, all bets are off, bleach away, or toss. I think this washing and then bleaching business hails from uptight town, and has no business playing in the dirt with me, and mine. You rock, GB! Sally forth!
I’ll also only brush pots, sometimes very lazily, and have yet to have unhappy seedlings or unhappy repotted plants! Agreed that it’s a bit too much; I focus on having high quality potting soil and good conditions to grow.
Agreed, it’s all about good soil for me!
As a Master Gardener in Training, I have also been told to wash pots thoroughly and disinfect using a diluted bleach solution. However, in my own garden, I have started to relax a bit and am now just giving pots a rinse in warm water, perhaps a scrub if there is any caked-on dirt, and that’s about it. Saves a ton of time and I have seen no ill effects as of yet. For commercial operations, I can definitely understand that it may not be ideal to chance it.