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

Very well said, Thank You!

You point out the reason I've come to this forum less and less. I've gotten frustrated with everyone giving recommendations with no scientific evidence (or a grounding in reality). I used to spend the time to try and correct misinformation while offering scientific based explanations and recommendations, but I don't have time for that anymore.

Just to offer an "on the other hand", and "take the other side", several people have cited studies that were done scientifically, showing something specific about supplying bottom heat to germinating certain seeds providing no benefit (under certain specific conditions and defining "no benefit" in a precise and specific way that was easy for them to measure).

Then those studiers were translated or mistranslated into something like "no one should ever use bottom heat because it never has any advantage of any sort to anyone".

The overwhelming evidence to the contrary (contradicting the mistranslation, not the study) may be anecdotal because it was not obtained or documented under tightly controlled conditions and then peer-reviewed. But there is a difference between "anecdotal" and "useless". The determining factors are HOW sloppy our "before and after" tests are and how much they came from "I did this", and how much they came from pass-along hearsay.

I would also argue that there is more value to thousands of people doing something and forming an opinion, than there is in a dozen people doing it.

I also use a "plausibility" test.
- Seeds germinate and emerge faster at different soil temperatures.
- A seed catalog or an Ag text shows many or most seeds' optimum germination temperature over 70F.
- Some seeds' optimum germination temperature is above 80 or even 85 F.
- Slow seedlings straining to overcome adverse conditions may be more subject to diseases and (anecdotally) don't always recover and "catch up" from early stresses.
- Most commercial growers spend money and energy to control germination temperatures, and they aren't stupid or knowingly wasteful.

The ultimate benefit of a germination heat mat may be subtle, or only accrue to some gardeners, or only observed outside of ideal lab conditions, but this is one case where I trust the large % of gardeners who think heat mats improve their results, over the [u]applicability and relevance[/u] of loosely quoted studies that found one set of circumstances where one specific metric was not improved by the use of a heat mat.

Or consider a thought experiment.

The seed starting room air temp is 55-60 F.
The seeds are peppers and eggplants.
Optimum germination for them is above 85F.

At 55 degrees or less (soil is usually colder than air, at least indoors) , will they come up in time for summer, or ever (before they rot), or before the cat knocks the tray over?

Or will they struggle to the surface and succumb to damping off or TMV or aphids before they're 3" tall?

This is just an "on the other hand" suggestion. I value the results that come from controlled experimentation, but the value of science is not in one or another study, but rather in the accumulated consensus of dozens of studies that agree.

it's also important to find and define the areas of relevance of any one study's conclusion. That's usually advanced by one research team "showing up" another team by finding an exception to their rule, or varying some previously un-thought-of condition that reverses some aspect of the first team's conclusions.

The PhD version of "Naah Naah Nye Naah Naah, so THERE!". Now that's Real Science!

Kindness please.

Sorry, it's difficult to understand your logic here... It's not sensible to support scientific controlled studies on one hand, but then to throw them out on the other hand by presuming that they're only valid in some sort of "ideal lab conditions".
If you haven't done so, I'd suggest you read Deno's publications - which are easily accessed these days - and also Henry M. Cathey's 1969 publications in Florist's Review on heat mats if you can find them (and if you do find them, please let me know how). (Deno summarizes Cathey's findings.)

This message was edited Mar 15, 2013 11:19 AM

I'm not trying to be contentious or arbitrary.

The main reason I question this result and not some others, is that real-world experience by pros and many careful hobbyists flatly contradicts what was alleged as someone's conclusions about laboratory-controlled situation.

The mis-quoters aroused my ire. Just changing "usually" to "always" and then sneering at the entire gardening and agricultural population as superstitious dullards got me going. (That was some other thread, in a forum far away and long ago.)

I'm curious to know what Cathey actually tested, and whether tomatoes, peppers and eggplants germinate and emerge just as fast at 70 as 80-85.)

Also I know Deno worked with small numbers of mostly-esoteric seeds, mostly ornamentals and wild seeds. (Plus he states that he tested at 40 and 70F, not above 70). I thought he tested hardly any common garden crops, but apparently he must have tested some (at 70).

I found it!

SEED GERMINATION THEORY AND PRACTICE SECOND EDITION
pp. 3-4 in the Second supplement

Deno said:
"Secondly, a century ago temperatures inside houses were colder than the 70 which is now customary. In such colder houses bottom heat was beneficial in order to raise the temperature to 70."

First, everything said there SUPPORTED the idea that 70F is needed by many seeds to get even "satisfactory" germination. Greenhouses, basements and bedrooms BELOW 70 F usually or often benefit from germination bottom heat. That could be the end of the debate from my perspective.

My original objection stands: misquoting a scientist who made some SPECIFIC claims based on specific controlled tests into "ALL you people are dumb for ever using heat mats" is a misuse of the empirical method.

(It is also often hard to extrapolate from a lab into the real world. You have to allow for the different conditions and expectations. Deno's "satisfactory" might be someone else's going out of business due to increased heating costs or slow germination.)


I read what Dr. Deno said as "I have studied germination at 40 and 70 for most of the species studied by Cathey and confirm that germination at 70 is satisfactory."

So he did not test warm-weather crops above 70 himself.

What was "satisfactory" to him, with small numbers of seeds in sterile paper towels may not have been "optimum" compared to many thousands of gardeners and market growers and nursery people starting millions of trays of seeds.

He cited Cathey's data (or conclusions) as :
"Germination was usually optimum around 70, and temperatures down to 50 or up to 85 often result in markedly lower germination."

"Usually" and "often" are not "always" and "never". If they are saying that "most" seeds don't need bottom heat in a 70F room, well, duhh, yeah.

I need to look at the specifics of Cathey's tests, criteria and data to say anything more. But also, from the time I spent doing tissue culture and cancer research, I know that I need to ask myself what axes Cathey and his/her team were grinding. What have they been trying to convince others of, for the last 10 years? Every scientific paper (every text of every sort) is written by someone with opinions, motivations and biases that might be conscious or unconscious. Cathey might be a saint, or might be a normal scientist (normal human).

The example I use is the study funded by the National Peat Association (something like that). They showed much worse seedlings did (in their lab, in their tests), with coir instead of Wonderful Peat. If you read carefully enough, you might notice they never washed the coir and bought it "wherever". Then if you read another graph carefully, you might tell yourself "LOOK at all that frigging SALT!!". Duhh, yeah, the seedlings barely survived the terrible choice of the coir supplier." But their conclusion was not "flush the coir if you buy a bad batch", it was "seeds germinate MUCH better in our product than in coir. Coir stinks and no one should use it".

More likely, Deno and Cathey both found something "satisfactory" because the species and conditions they were most interested in, and their criteria for success, agreed with their conclusions, not someone else's real-world needs. Like air temperatures below 70, or below 85.

= = =

It's more interesting that these two concluded that "everyone else is wrong" about any crop seeds benefiting from soil temps above 70. (Or did they claim "usually" and "often", for most species, instead of "any"?)

Deno states that he (Deno) tested at 40 and 70, as I thought, yet then makes this claim:

>> "Both Cathey's results and my own indicate that temperatures above 70 are neither necessary or desirable for germination."

Maybe they did not desire fast germination! Deno seems to find germination after 6 or 10 weeks just fine, but I think nurseries prefer 6-10 days if they can get that with a little bottom heat.

I'll need to find and look at Cathey's data to see how many hot-weather crops he or she tested. Also, I would need to find the rationale behind "not desirable". If they don't care about speed of germination, or are talking about situations irrelevant to the people who have extensive experience with bottom heat working better for them, that would explain the disconnect.


I was trying to make some distinctions:

- Carelessly repeating hearsay without asking "how many people TRIED it both ways" is bad.

- Giving some consideration to an observation made by thousands of professionals on millions of seed trays over many decades and at least some careful hobbyists is good.

- Reading one or two studies and then claiming they proved wildly more than they ever tested is bad.

- Reading any number of studies and then drawing b road conclusions without citing the limitations of each study doesn't get any traction in scientific circles and shouldn't from uis, either.

Concluding much of anything based on 1-2 studies is actually very bad. Technical literature is FULL of studies (and years worth of repeated studies) that were then contradicted (or explained) by later studies that said in effect "but what about THIS variable??"

Like noticing that the Phosphate concentration in the buffer had a huge unanticipated effect on tissue culture growth, when five years of smart PhDs all thought "Oh, that just controls the pH, we always use PBS". Switching from Phosphate Buffered Saline to Ringer's solution or Ringer's Lactate could give TOTALLY different results about blah-blah-blah cellular interaction. They weren't lying or even wrong just irrelevant to what they thought they were studying (conditions inside HUMAN tissues).

The real world is complicated. Lab research is hard. Applying lab reults to the real world is REALLY hard.

When a few studies contradict huge amounts of carefully-collected real-world experience, maybe a few more studies are needed. Maybe they should go into commercial greenhouses in Alaska and try to start 10,000 tomato seedlings at minimum cost. When they tell the owner "now dial your air temp up to 70 F +/- 1 F", maybe their research funding will pay for the new heaters and all that oil.

Not that I know how Cathey did his or her tests, or what factors I would ask to be re-checked by independent teams.

But the real world is much more complicated than any lab. No one can test EVERY variable or even reliably think of all the relevant variables.

Or maybe both Deno and Cathey were exasperated by stupid people who thought that EVERY seed needs as much warmth as eggplants and peppers.

More likely they knew how to avoid ever damping off, drying out, aphids, cold drafts, mites, intermittent over or underwatering. Or cats that will pee in a pot if the seedlings don't come up pretty quickly. If it was a variable that they didn't test, that "laypeople" don't control perfectly, lab results are just not relevant to real world "laypeople" until enough different te4ams te4st the same theory in different ways to stumble onto the RELEVANT real world issues (molds, fungi, drafts, underwatered weekends, cats ... ).

Or maybe I'm wrong, and nurseries and greenhouses DO heat huge glass structures to 70, or let acres of seed trays sit around for three times longer than necessary, waiting for seeds to sprout.

Or maybe every resource I've seen that cites optimum germination temperatures for many crops are just untested superstition. I need to buy some Ag textbooks before I go too far down that road, just because some superstitious bumpkins start some crops indoors with heat.

Possibly I'm even wrong about peppers and eggplants germinating faster at 80 or even 85 than at 70. I thought those were no-one-would-argue examples.


Since Dr. Deno put all three into the public domain, I'll assume his permission to quote.

"Henry M. Cathey has already studied this question extensively, and his results were published in Florist's Review August 21, August 28, and September 4, 1969. He studied germination at five degree intervals from 50-85 F. Germination was usually optimum around 70, and temperatures down to 50 or up to 85 often result in markedly lower germination. I have studied germination at 40 and 70 for most of the species studied by Cathey and confirm that germination at 70 is satisfactory.
...
Both Cathey's results and my own indicate that temperatures above 70 are
neither necesary or desirable for germination.
...
Why have temperatures above 70 have been recommended so often? Many of
the recommendations in the literature are inferential such as recommendations to use
heating cables or place the seed flats on hot pads or other warm surfaces such as the top of a refrigerator. There are possibly two reasons for these traditional concepts. Many greenhouses in spring may be at temperatures significantly below 70 and particularly the soil temperatures are below 70. Bottom heat could be helpful.

Secondly, a century ago temperatures inside houses were colder than the 70 which is now customary. In such colder houses bottom heat was beneficial in order to raise the temperature to 70."

P.S.

Persistent URLs for Dr. Deno's book
"Seed Germination, Theory And Practice"
and supplements:

http://hdl.handle.net/10113/41278 (1993)
http://hdl.handle.net/10113/41279 (1996)
http://hdl.handle.net/10113/41277 (1998)

(I think six pages is my longest forum post ever!
Apologies to anyone wearing out their "page Down" key!)


This message was edited Mar 15, 2013 9:10 PM

P.S. I'm not making my main point up. Here's a list from Thompson & Morgan.
I skipped over anything whose lower limit for recommended germn soil temp was below 75, then only scanned A+B+C.

Abelmoschus - - - - 75-80
Araujia - - - - 75-80
Aristolochia - - - - 75-80
Cacti - - - - 75-80
Caesalonia - - - 75-80
Cordyline - - - 75-80
Crossandra - - - 75-85

But spank me, they cite 70-80 for tomatoes!
Solanum 70-80


http://tomclothier.hort.net/page11.html

Tom Clothier is respectable and not a seed vendor.
He cites 86 F as fastest emergence for eggplants, Cucumber, Muskmelon, Okra,

He cites 77F as optimum (fastest) for tomatoes, peppers and many others:

Johnnies Seeds cites similar optimums, many above 70F.

Asparagus, lima beans, snap Beans, Beets,
Cabbage, Carrots, Cauliflower, Lettuce,
Peas, Peppers, Radish, Sweet Corn, Tomatoes and Turnips.

If Deno and Cathey are just saying that no one should care about fast or slow germination, OK, they have free speech too.

And those last two posts illustrate the other reason I spend very little time on this forum (or site). Long ranting posts that are way off topic. I've come to the conclusion that there are only about 10 people here who actually know how to create a thread and everyone else chimes in to discuss anything that pops into their mind.

It also reminds me of my days as an Extension Specialist when someone would come it with a "terrible problem" and "desperately needed my help" I'd take time, research a solution for them and talk them through it - they would then spend the next half hour telling me I was wrong and didn't know what I was talking about because Aunt Sal told them to do something her Aunt told her about when she was a kid. It was frustrating then and even more so now.


Bye

I agree....this is becoming ridiculous .....please just stop :(

trc65, Debsroot
I agree 110%.

Spring FEVER!!

I also agree wholeheartedly.

I personally enjoyed reading Corey's long messages, and although I might not agree with everything he said, I appreciate that he took the time and effort to put that information and those viewpoints here. My guess is that, right about now, he is reminded of that old saying, "No good deed shall go unpunished."

I also appreciate the information and viewpoints provided by other responders. We have strayed from the original topic of "To Bleach or Not to Bleach?" and that is still an open question, as it probably should be.

It always puzzles me that a long post bothers anyone. With the Page Down key, it takes less than 2 seconds to scroll past the longest post, But it takes 10 times as much work to say "I don't like the way you post".

Still, many6 people feel strongly about thread drift, so I'll defer to the wishes expressed above.

I guess I don;'t always wait for the original topic to peter out before I drift off-topic, but no amount of thread drift ever prevents anyone from saying anything they have to say on the original topic .

If altagardener, with whom I was speaking, wants to continue, we can do it by private Dmail.

Thanks, Zen-Man .

Its been awhile since I visited this question I first posted in Feb. I didn't sterilize, just washed with warm/hot water, allowed them to drip dry and reused them So far all my seedlings look good. I have four 72 cells trays and two 18 cells trays of toms, peppers, onion, broccoli, etc. We'll see and I'll report back. Hopefully I didn't screw up by not heeding trc65s advice. Also I didn't realize that damping off was anyway related to bleaching my stuff. Guess you learn something new everyday.

Here are my seedllings growing in 6-packs and 3" pots that have only been washed and airdried. No sterilization and no damping off....ever!

1] Daylilies in 6-packs March 23, 2013 and not one died from dampingoff.
2] Closeup
3] Daylilies in 3" pots that have not been sterilized and not one.
4] 156 Daylily seedlings in the nursery on May 2012
5] Dayliliy seeds sprouting with Deno method just prior to planting in 6-pack. This may be the reason why no damping off.

Thanks blomma. Makes me have hope for my choice! I'll google "Deno method".

You are welcome.

You don't have to Google Deno. It is just to soak the seeds overnight in hand hot water to plump them up and soften the seed cover. Then place in a moist paper towel inserted in a ziplock bag. If perennials need stratification (moist cold) , place in fridge for 2 weeks. If not, place in room temp.

By the way, I have trays that were purchased in 2002 and after a cleaning, I reuse them to hold pots.





This message was edited Apr 8, 2013 6:15 PM