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To Bleach or Not to Bleach? What is best to reuse seed trays

Bismarck, ND

I've been starting my own garden veggies for the last few years and now I have quite a collection of used trays and cells. Each year I purchase new cells but I really would like to start using my supply. I've been reading that using bleach is a good way to sterilize stuff but I've also read that using bleach is not a good idea. Any thoughts on Bleach or Not to Bleach?

Galesburg, IL

I have been using bleach for about 20 years to sterilize both in commercial operations and personally. I don't know why anyone would say it is not a good idea.

Remember, before you bleach your trays/cells, they need to be washed and not have an overabundance of potting soil/dried plant material on them. I usually wash trays cells as soon as they are emptied that way they are ready for bleaching when I get to it.

I use a large Rubber made trash can for bleaching, large plastic totes also work well - all depends on the quantity of material you have.

Everett, WA(Zone 8a)

I only garden on a tiny scale, but I also try to wash inserts and trays and plastic pots as soon as I get the soil out. I think it is good to get all visible soil off ASAP, so soil organisms aren't encouraged to form spores.

Well, I spray them with a hard mist and spray from a garden hose hand sprayer. I let batches of trays & pots stand a while, wet, to soften up, and try to spray the rest of the soil off. It helps to have some kind of corral like chicken wire or fencing to hold things in one place while I blast them.

(The mist conserves water, but the spray scrubs harder. I use the spray in short blasts and use the mist continuously.)

Then I rub and scrub any remaining visible soil or stain that didn't come off easily and and spray again.

(Typically, they next sit in rain and sun for a while. I'm sure that rain and sut bring in more microbes, but hopefully few plant pathogens.)

Then, when I have time and I've collected a lot of plastic gadgets, I make sure they're still visibly clean and spray them all again anyway, to get the dust off, to soften remaining films, and to protect my dishwasher and drainage pipes.

Then I run them all through a dishwasher, briefly. I fill it up and run it for a few minutes, then remove that bunch of trays and replace with other trays. So one complete cycle of the dishwasher might handle 5 batches of trays. Afterwards, I let the soap sit on the trays for a while, then rinse them all with the hard mist from the garden hose, outdoors.

Probably a big barrel of bleach is better, but I found that kind of dunking very tedious and tiring with just a 5 gallon bucket. At least I get mine visibly clean, then hit them with hot, caustic , soapy spray.

If I start seeing plant diseases, I'll have to find a bleach-dunking method that works for me. Maybe hand-spraying in my bathtub. That would have the side-benefit of getting my tub really clean!




Carmel, IN(Zone 5b)

I've been using bleach on my trays/cell packs/pots/capillary cloths for years, and have never had a problem with diseases or damping off. I think it's important to use the proper amount of bleach, and to rinse thoroughly.

I do try to remove as much dry potting mix before soaking, and I use a bottle brush to clean out the pots/cell packs. It's rather a labor of love, but my seedlings and plants have all thrived in pots/trays that have been used for several years.

Linda

Everett, WA(Zone 8a)

How many years do your capillary cloths last? Are they commercial, and what brand name?

I've been using cotton flannel, and they look pretty beat-up after a few months in a tray, especially if I s0pill any soilless mix.

Carmel, IN(Zone 5b)

Rick: I bought some capillary mats from Lee Valley (actually, it's a large size that you can cut to size) that holds up really well. I also purchased some from my Master Gardeners group. I will check where they purchase from because they are really sturdy also. At MG, we pay cost, so I can buy them for $1 each.

Will report back as soon as I can find out.

My mats from both sources are at least a few years old and have held up well to a mild bleach solution.

Everett, WA(Zone 8a)

Great. I've been looking for an excuse to order from Lee valley since I saw their tiny seed spoons. Others have praised the Lee Valley cap mats.

I keep hoping they will re-stock either of certain small-knife-sharpening guides that have been unavailable for decades. Mine both got lost during a move. "Buck Honemaster" was one of them.

Thanks!

Calgary, AB(Zone 3b)

I wonder if it may depend on the conditions in your area - if you're in a humid area, is there a larger amount of fungal/mildew spores floating around and a greater propensity for fungal disease to spring up where conditions favour it, both inside and out? Anyway, i've always gardened in relatively dry, low humidity climates and have never bothered bleaching pots, or even washing them, or sterilizing soil or any similar measures. Over many years and starting a lot of species from seed each year, I've never been bothered by damping-off. I also re-use soil from year-to-year, as I usually knock most of the soil off the roots prior to planting seedlings in the rock gardens.

Everett, WA(Zone 8a)

AltaG, I think you're right. It depends hugely on local conditions.

Dr. Carolyn, in the Tomato forum, made a point about safeguards against diseases like soil diseases. (For example, rotating cops.)

If you never have a certain problem, don't worry about it, and don't take burdensome measures against it. If certain pest or disease isn't a problem in your climate or your soil type or under your conditions and practices, "it ain't broke".

But when you DO have problems with X, Y, or Z, then you do have to discover and use effective counter-measures against them.

Carmel, IN(Zone 5b)

Rick: the seed spoons from Lee Valley are my favorite gardening tool outside of my garden knife. As I get older (and it gets harder to see tiny seeds even with my bifocals) the spoons are a godsend--really easy to get just the right amount of seed where you want it placed.

Lee Valley occasionally runs free shipping--sign up on their website for notifications. (And no, I don't work for them LOL)

Jackson, MO(Zone 6b)

I live in a hot humid area. I don't take the time or spend the energy bleaching my pots. I have never had a problem with mold.

(Pam) Warren, CT(Zone 5b)

I had a huge problem with damping off the first year I I tried to start seeds for this garden. I had been quite successful in a previous zone so it was quite a shock, I can tell you! Thanks to DG, I began using peroxide for all watering ( formulas vary some, I use 10:1), including wetting the soil mix before use. That was the end of it. Also since then I stopped worrying about sterilizing anything. The only other thing I do religiously is sprinkle cinnamon on top of the cells and pots after sowing or transplanting, which prevents gnats. I think I read somewhere that it may also act as a fungicide, but I'm not sure about that.

Pam

Irving, TX(Zone 8a)

Pfg
will it be the same to add Cinnamon to the water? instead to sprinkle it on the soil?

(Pam) Warren, CT(Zone 5b)

I don't know. I think I've read hat some people add it to the soil..

Bismarck, ND

I was gone for a while and pleasantly suprised by the number of reponses to the bleach question! Again its a mix of "have used" and "not used" but nobody sounded an alarm about NOT using bleach so I think Im going to use a 10 to 1 mix and wash the trays and since the 9 packs are fairly cheap I think I'll recycle and replace those and reuse the larger cells for potting up.

(Pam) Warren, CT(Zone 5b)

There's nothing wrong with using it, for sure. We're just all over the place about how necessary it is. So many variables...

Pam

Victoria, Australia

When starting seeds indoors, it is essential that the seed flats and trays are cleaned and disinfected before reuse.

If they are not disinfected properly, seedlings will likely suffer from damping off (which will kill the seedlings at the soil level). This is one of the things that makes starting seeds indoors much more time consuming.

Wipe the loose dirt out of the flats and trays. Next is to wash them in soapy water to remove the hardened on dirt. Then to disinfect them, soak it in a 5 gallon bucket of a water and bleach mix for 15-20 min. Use the recommended 1 part bleach to 9 parts water solution. Finally, rinse them, let them air dry and they are ready to use for starting seeds.

Wakita, OK

We've also had good success with soaking pots and trays in a solution using a commercial sanitizer available at Sam's. It's only about 6 dollars for a large bottle of concentrate and doesn't irritate my asthma like bleach does.

Calgary, AB(Zone 3b)

Quote from nelsoncastro :
When starting seeds indoors, it is essential that the seed flats and trays are cleaned and disinfected before reuse.
If they are not disinfected properly, seedlings will likely suffer from damping off (which will kill the seedlings at the soil level).


Well, this is the variability being discussed... I don't find it necessary at all for starting seeds indoors, and it seems others find the same. Evidently, in your conditions, it is necessary. I wonder why?

Everett, WA(Zone 8a)

For me, the biggest variable seems to be how wet the surface of the soilless mix is, and how 'open' the mix is.

Then, for slow seeds, whether they have been pre-soaked (Salivia)

After that, and I'm guessing now, running a little fan even part of the time seems to help them stay healthy.

Also, if I leave some seedlings in tiny cells TOO LONG (like 72 or 128 cells per tray), nothing can keep them from dieing. But preventing the bottoms of the cells from being waterlogged (with perched water) gives them an extra few days before they die.

Casper, WY(Zone 4a)

Since Nature does not sterilize her ground I don't sterilize my seeding trays. I just wash them as they get emptied. Never had any problems. Can't see making more work for myself when it is not necessary.

Everett, WA(Zone 8a)

>> Never had any problems.

In my mind, that's the key phrase, especially after filling in the subject: YOU don't have a damping-off problem or soil-born diseases. I used to have entire trays of seedlings die, so I use a few of the tricks. Not Clorox or peroxide yet, but I bet many of the people who do, need to, for one reason or an other.

>> Since Nature does not sterilize her ground I don't sterilize my seeding trays.

That, on the other hand, is an argument form with which I respectfully disagree. (Or you might have been rhetorical.)

If I succeeded in duplicating EVERY relevant aspect of nature, it would be more persuasive, but I'll stick with your other argument instead: what works for you, does work for you. What works "for nature", might not work for everyone who starts seeds indoors.

I'm probably not DISagreeing with you, maybe I'm just splitting hairs.

Nature is perfectly happy with 1% germination and 2% survival of seedlings if the plant drops 10,000 seeds.

Nature is perfectly happy if entire varieties and species die off if they c an't hack it in that locale: there's
plenty more species where they came from.

If a spot takes a few dozen generations (or 100 generations) to re-populate, that just provides a niche for new varieties to develop.

Nature seldom treis a warm-season. long-seson crop in a cold, short-summer climate.

Nature usually provides deeper drainage than my 2-3" cells provide.

Nature provides air that moves and isn't stagnant, and smells better than my indoor air!

Nature provides brighter light than I provide

Nature provides an entire population of soil microbes many of which are beneficial.

Nature seldom over-waters as much as I do (a skill I'm sure you and most gardeners have mastered).

(I'm not trying to be contentious, but I hear the suggestion that we should imitate nature more often than I agree with it.)

Casper, WY(Zone 4a)

Well Rick, I will just say this. I have gardened in 4 states, and altogether for 45 years. So, if nothing drastic has happened from not sterilizing in all those years, I don't feel the need to waste time when not needed, I think I am doing fine.

The states that I have gardened in was NY, MA, NE, and now WY. I didn't sterilize in any of them. In all the years I have gardened, I learned what is important and what isn't.

I scrape off any dirt, including lime deposit on pots and trays. Then wash with hose and scrub with SOS, rinse and leave in the sun to dry. I just don't sterilize in bleach or anything else.

Everett, WA(Zone 8a)

I'm pretty sure there is something that you're doing that prevents damping off. If we identified that, and everyone was able to do that successfully, probably no one would need to bleach pots.

I assume that you would agree that many people DO have problems with damping off?

(Hmm, it would be interesting to try to measure whether someone WITH frequent damping off problems had fewer if they started using bleach BUT did everything else the same way they did before. I know that I changed many things my first few years of seed starting, and then picked ONE of the changes as the "reason" I stopped having damping off problems.)

>> leave in the sun to dry

Maybe you're getting UV sterilization ?

More likely, something about the way you water, or provide air circulation, or the seed-starting mixes you use prevent damping off.

(Pam) Warren, CT(Zone 5b)

Peroxide. No damping off.

Calgary, AB(Zone 3b)

Quote from RickCorey_WA :


>> leave in the sun to dry

Maybe you're getting UV sterilization ?

More likely, something about the way you water, or provide air circulation, or the seed-starting mixes you use prevent damping off.


I don't leave pots in the sun to dry, since I don't wash any pots; I top water; I've never used a fan or anything to promote air circulation; and I use a variety of soil mixes (all starting with commercial potting soil but reused year to year) depending on what I'm growing (border perennials or alpines).
So, go figure...

Everett, WA(Zone 8a)

Successfully re-using soilless mix from year to year is the most amazing. Do you put some of your own compost into each batch? If you have some potent friendly microbes that prevent damping off, you could sell them and get rich!

I think we need to follow you and blomma around with video-cameras to see what magic thing or things you do that prevent damping off!

I see from PlantFiles that you're also very experienced.

(I assume you meant that you do all those things above, but still DON'T have many or any seedlings lost to damping off. And you don't sprinkle pixie dust o mist with various potions. )

I usually assume that perennials and alpines will be pretty slow-growing for their first few inches, hence most vulnerable to D.O.

I'm going to bookmark your post so I can point other people to it as proof of "on the other hand ..."

P.S. Can I ask how you store seed-starting mix from year to year so you c an re-use it? Do flush it? Does it freeze all the way through?



This message was edited Mar 13, 2013 2:50 PM

This message was edited Mar 13, 2013 2:52 PM

Northeast, PA(Zone 6b)

If someone has problems with damping off, it would be interesting for them to run an experiment. Sterilize half the pots and don't the other half. Start same seeds in these and see if there's a difference in damping off. (Obviously water the same & have same airflow over both).

I haven't had any problems with damping off. I sterilize my pots just because... I have a huge double laundry sink so I fill one side, add bleach and soak the pots, swish them clean with a brush, rinse & air dry. But I don't know that it actually makes a difference that I add the bleach. The sink is awfully large so its probably not at the recommended strength and its open a long time with several batches of pots so it probably gets weaker with each batch (yes - I wash A LOT of pots each year).

Tam

Everett, WA(Zone 8a)

Tammy,

>> I haven't had any problems with damping off. I sterilize my pots just because...
>> But I don't know that it actually makes a difference that I add the bleach.

I bet that describes more than 75% of most people's garden practice and garden advice.

"I always do it this way ... and it works for med."

Once we read 4-5 people saying that, we start telling each other: "we HAVE to do it THIS way ...."

I very seldom be controlled experiments, even though I love to fiddle and play at "making science".

Sometimes I think that our "special tricks" just remind us how careful and virtuous we're being. In my case, maybe it helps me to overwater a little less, and that makes all the difference.

Calgary, AB(Zone 3b)

Quote from RickCorey_WA :
Do you put some of your own compost into each batch? P.S. Can I ask how you store seed-starting mix from year to year so you c an re-use it? Do flush it? Does it freeze all the way through?


No, I've never added compost to my soil mixes so there's certainly no "potent friendly microbes" being added. The soil I reuse is just dumped into large Rubbermaid storage bins that are kept in my basement potting area until next usage - no flushing (whatever you may have meant by that?), and no freezing.

Everett, WA(Zone 8a)

>> no flushing (whatever you may have meant by that?),

I usually flush some water through a container "to remove excess salts" or left-over fertilizer. But I guess that seed-starting containers don't get much, if any, fertilizer added.

Something you do must be pretty wonderful if it prevents damping off even while re-using mix and pots from year to year without washing.




Calgary, AB(Zone 3b)

Quote from Tammy :
If someone has problems with damping off, it would be interesting for them to run an experiment. Sterilize half the pots and don't the other half. Start same seeds in these and see if there's a difference in damping off. (Obviously water the same & have same airflow over both).


Yes, I agree totally! That would be a great first step towards an actual controlled experiment! Seed-starting advice on these forums and in general suffers, IMO, from a huge lack of scientific reference - people draw hard and fast conclusions from information that is anecodotal. Note: Some information, though it is anecdotal, may be based on a lot of repeated observation and may be sound though it is not based on controlled experimentation. However, I think the vast majority of anecdotal information is not necessarily well-thought-out, and is not based on a lot of knowledge, or experience and observation. For example, a single experience may often be the basis for an opinion that becomes the only possible truth for that person.

On public forums actual scientific evidence (e.g. Dr. Norm Deno's findings) tends to get shouted-down or is simply overwhelmed by the all anecdotal advice. A large part of the anecdotal stuff (though not all) consists of people advising other people to do random things that can't be supported by any chemical or physical reasoning. What I mean by "random" and "insupportable" are various things I've read, e.g. chill seeds in fridge overnight (this was in a published book purporting to tell people how to start seeds), soak seeds in apple cider (Why apple cider, if soaking is the goal, rather than plain water? "Because it's an acid"). One can see how these bits of "advice" probably came from a distortion or misunderstanding of findings from actual studies. I suppose the "overnight in the fridge" bit is some miscomprehension of what stratification is about, and the apple cider bit may be some misunderstanding of what sort of strength of acid would actually be needed to make any difference in dissolving through a hard seedcoat. Anyway, very interesting subject.

Calgary, AB(Zone 3b)

Quote from RickCorey_WA :
>> no flushing (whatever you may have meant by that?),

I usually flush some water through a container "to remove excess salts" or left-over fertilizer. But I guess that seed-starting containers don't get much, if any, fertilizer added.

Something you do must be pretty wonderful if it prevents damping off even while re-using mix and pots from year to year without washing.


I use very little fertilizer. I want sturdy, compact plants, not soft, loose ones.

I'm not doing "anything wonderful" - I am doing the absolute minimum!

Calgary, AB(Zone 3b)

Quote from RickCorey_WA :
I'm pretty sure there is something that you're doing that prevents damping off.


Maybe it's the other way around... are people doing something that promotes damping-off? E.g. excess watering? If bottom watering, do pots sit in water? Not removing cover as seeds germinate?

This message was edited Mar 14, 2013 1:16 PM

Everett, WA(Zone 8a)

Yes, that's exactly the kind of thing I mean.

You don't think you're doing anything special, and yet 90% of beginners DO have damping off. Something like 2/3 to 3/4 of experienced gardeners have enough problems with DO that they jump through some hoops to prevent it. Many or most commercial growers sterilize or throw mix and pots away rather than risk re-using them.

(I usually figure that if PROs spend on something, it IS a problem for most people.)

So something or things that you and blomma do, that you don't think are special or noteworthy, ARE giving you results that many people can only achieve by jumping through hoops and spending time, energy and money. If you could bottle it and patent it, you could be rich! Maybe something rare and precious like "common sense"! :-)

"Too much watering" or "too-wet surface" or "humid air" are all highly probable suspects. Everything I read used to say "dirty pots or re-used mix or dirty mix", but now I have to question that wide-spread belief. It does not apply to everyone!

There are many anecdotal reports of "I used to have DO, but now I bottom water and that cured it".
And "I used to, but now I sprinkle grit or Perlite and it stopped".
And "I used to, but now I water with H2Os and it stopped".
And "I used to, but now I sprinkle cinnamon and it stopped".
And "I used to, but now I water with Chamomille tea and it stopped".

In my case, I used to have a lot of DO and non-emergence, but now I do blah blah blah and have never seen it since. I THINK the faster-draining mix and coarse non-water-holding top-dressing and maybe the fan are the cures. But maybe without knowing it, I ALSO learned how to avoid over-watering, and I just don't realize I did?

Maybe it's all about having enough air in the mix. The evidenc e is not c ontrolled enoguh to conclude anything "scientifically".

>> Not removing cover as seeds germinate?

That may cause terrible problems to beginners, but there is such a loud, unanimous online chorus of "take the done off AS SOON AS the first sprout emerges", that I don't think many people make that mistake twice. Not if they go online to ask for advice!

Everett, WA(Zone 8a)

Altagardener,

>> people draw hard and fast conclusions from information that is anecodotal

>> For example, a single experience may often be the basis for an opinion that becomes the only possible truth for that person.

>> and may be sound

Those were really well said and I agree with all of the above.

I think that MOST gardening advice comes from hearsay and "this worked for me, so it is the best or the only way".

My approach is that if several people I respect say THEY do it a certain way, I'll try to imitate them as a starting point to see if I can find something similar that works for me. Then I either adopt that as My One True Way, or keep doodling with variations that amuse or interest me - or seem cheaper or easier or more fun.

I have the same "My Way" disease that many people have. Once I come up with "My Way", and happen to like it or be proud of it, I'm stuck in that rut for a long time, for good or for ill.

But I don't care if 100 people all quote the same common knowledge. That just means that we all know the same old tales or read the same websites. One person who says I DID THAT knows more than 100 people who read about it.

One person who tried it several different ways and noticed different results under somewhat controlled circumstances knows more than 10 people who "always do it the same way".




This message was edited Mar 14, 2013 2:59 PM

Everett, WA(Zone 8a)

Probably my silliest gardening habit is that I want things to "make sense to me".

Silly, right? If it works, why should I care WHY it works? I'm not sure, but I want to know "why"! Then maybe I can think up some other way to get the same effect, even better adapted to my conditions and my own preferred habits.

I don't care if "everyone" knows something or does something: if I can't dream up some pseudo-plausible mechanism that explains why it "should" work, I'm suspicious of it. I want to find a different way that "makes sense to me".

Or I want to doodle around with variations on the "thing that makes no sense" (to me) until I see some result that hints at what is really going on. Or it may even work better for me!

Since I seldom put very much effort into real controls, it's Lazy Science or pseudo-science or just pottering around for entertainment.

Irving, TX(Zone 8a)

ooohhhh i have a big headache my English is not so good to understand all of those words ... oohhh

What if I tell you that I "never" cleaned or sterilized my pots of soil ... I never had any of those problems ...

Everett, WA(Zone 8a)

I'm not ranting for or against bleach or anything else. The last two posts were just rambling about the intersection between hobby-gardening and the semi-scientific method or pseudo-scientific method ... or the lengths to which I will go in order to entertain myself!

People who use the practical method of "this works for me" and "I avoid unnecessary work" are certainly more practical then I am, and in that sense much smarter.

I suspect that anyone who does large volumes of seed trays may HAVE to give more consideration to "least effort" than I do with my 4-6 trays per year.

As it happens I don't bleach or re-use USED mix. I don't even water seeds with potions or sprinkle with pixie dust (but I keep intending to water with H2O2 'just because it sounds like a good idea'.

I do save UNused mix and bark from year to year under not-very-clean conditions. I always clean seed trays carefully and usually clean bigger pots reasonably well. Why? At one time I thought those were necessary and now they are a habit.

I'm passionate about very fast-draining, very-well-aerated mix, because that's my pet theory. Many other people get good results with peaty mixes and without obsessing as much as I do: some day if I get tired of pine bark I may evolve in their direction.

And every time I set up a tray and every time I water or refrain from watering, I think about whether I'm still over-watering and argue with myself about it. Probably that is where I should focus my attention, but I've chanted "moist but not soggy" and "damp but not moist" ... or is it "moist but not damp" until I'm dizzy.

My new mantra is "just barely NOT DRY".

Or I'll make up a Charles Goren Box for watering. There's a joke that Goren had a secret box that told him how to bid. After he died, people were allowed to look into the box. It had one piece of paper with one word on it. "PASS".

My Watering Box would say "DON'T water yet".

Everett, WA(Zone 8a)

Drthor, that is the topic of the thread.

I'm glad the three of you are chiming in with "I don't need to do anything special". Something like 70% of seed-starting people had trouble with damping off until they found some "trick".

I wish you (you three) knew what it was that you're doing that prevents the problem, and could teach it to me, and to professionals who currently spend a lot on steam, bleach and new pots every year.

It might be as simple as "moist but not damp". Or being able to sense that these seedlings would wilt in another 24 hours so I WILL water today instead of three days ago.

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