interesting stuff kandm.... it makes sense to me, especially the fan idea.( hardening off gets to be a challenge here with the wind. no matter where i put them to harden off they seem to stress most even from the slightest breeze.) might as well try it to help strengthen them up. get out the feather duster and a lil fan give them movement once in awhile. easy enough.

Yes, one reason why the use of a small fan on seedlings is common practice.

Dave

I have long thought that thigmomorphogenesis was a neglected area where the hobbyists who wants to do some experimentation could work. On these forums back in '01 when there was a fad to test music and plant growth in school projects I suggested on these forums that a student could set up a cheap experiment using a CD, as we called it back then, of drum music and run some thigmomorphogenesis experiments. To my knowledge no one was interested. The fad then was to test Mozart.

BTW, Googling hits a lot of links to serious thigmomorphogenesis experiments in agriculture and forestry. It is not particularly strange or unpopular.

The "Transplant Production and Performance article I link to below is a pretty good read if you want to learn more about mechanical stress and thigmic response. Various types of thigmic stresses are discussed and evaluation. The author compares brushing with various items, wind, shaking manually vs with a machine and stress from some sort of an impediment; plexiglass, burlap etc The article also discusses treatment duration, timing (morning v evening) and frequency. (The paper is a bit old so if anyone can find a more recent study I would be interested to read it, thanks.)

The other article I linked to, the one titled "Bracing up...." had a good explanation of what's going on at a cellular level in the plant. It never occurred to me that the plant cells were actually growing differently based on their environment. I suppose I should have assumed it but I forget how responsive they are to stimuli.

"The indoor nature of the average seed-starting environment also influences the seedling's hardiness with regard to mechanical stress. Unless you arrange otherwise, the space under the lights is a calm, windless environment. Since moving air causes a plant to lose moisture faster, a windless environment contributes to the circumstances that encourage a thin cuticle. It also lends itself to the development of more slender stems, not adapted to the buffeting provided by the wind out-of-doors. Plants respond to mechanical stimulation (wind, raindrops, the gardener's dog taking a shortcut) by growing a bit slower and changing the way they build their cells. The cells end up shorter, stockier, and have thicker walls, making for shorter, sturdier plants. Without such mechanical stimuli, which are usually absent under the lights in the house or shed, the plant tends to make longer cells, with thinner walls. Nothing wrong with this; the plants are simply responding to the environment in which they are grown, and as long as that environment does not change, they're just fine. They are well adapted to that environment. But of course, their environment will change, and change dramatically, the day they are transplanted to the garden proper."

Here is a link that might be useful: Transplant Production and Performance Mechanical Conditioning for Height Control

Kandm, thanks for bringing the article to attention. It's one I've used when explaining the importance of hardening off seedlings...unfortunately many ask 'what happened' after the fact when conditions have gone wrong, rather than ahead of time when it's helpful :) Hopefully some new-to-seed growers will read and benefit. Or even some not-so-new-to-seed -- I did a pretty thorough job of burning the pomegranate seedlings on a windy day that I was going to gift to my sister, had to keep them another YEAR while they recovered, recently enough I should have known better.

I use to think I should baby seedlings if I wanted them to be successful, but the more I read about them the more I started to think about a 21 year old child living at home. If you want a child to move out you don't bring them breakfast in bed everyday. You harmlessly irritate them until they're ready to get away lolol!!!

morz8 wrote: Hopefully some new-to-seed growers will read and benefit.

Yes! I didn't know about this, and was wondering why my seedlings were growing so tall even though I have the lights right close to them.

Off to fan the little plants... Thanks very much! :)

Place the seedlings outside on days when the temps are above 40 degrees and the wind will do the same thing for you as running a fan. My seedlings go outside every available day when the temps cooperate. I have found that being so early in the season that the sun strength is nowhere near where it is in the summer and I haven't experienced any sun burning on the plants either.

A few of my plants were knocked over by strong winds last year and can testify that. I stopped last year using the stimulus(a fan and sloght blowing while looking at them) and the plants were substantially weaker to wind and other variables(animals mostly. This year I am starting to use the fan as stressors to promote its growth again. The problem with growing indoors is there are too little stress factors. so the plants will not try as hard. Do we try harder when something is easier? Same concept. My tomatoes all fell over due to a storm, they lived and produced twice as many toms as I usually get even in a larger field because the stems stopped growing up but rather out(these are not vine toms) so the plant didn't have to try so hard, with that being said the stress of it being outside in the elements it still grew vigorously and very productive.
Any other experiences?

Topics on this forum seem to come up in cycles. Back when I was a newbie everyone was recommending that you brush your hand lightly over seedlings daily to stimulate cell growth. I did this my first year and was charmed to find that 1/2" high lavender seedlings gave off a scent. I don't have any comparisons for NOT brushing plants, as to whether they do better or worse. I know *I* do better when I smell fresh lavender in February :)

gettingreenthumb wrote "The problem with growing indoors is there are too little stress factors. so the plants will not try as hard. Do we try harder when something is easier? Same concept. My tomatoes all fell over due to a storm, they lived and produced twice as many toms as I usually get...."

The vendors who manage the plants at my local Lowes have a policy if putting wind blown plants on the clearance rack. I am always wiling to buy these poor little castigated plants for 75% off because they generally do fantastic despite being blown around.

When trying to find out if I could put my seedlings outside in a cold frame instead of continuing to lug all the heavy trays up and down stairs from basement I found the originally referenced article on the Tomato Growing Forum.

I've been putting seedlings outside on shaded porch for over a week but am afraid they're still not "tough" enough to be moved outside even under cover of rigged up cold frame.

I left them out too long a few days and some foliage got a little dry or crinkled.

I got a fan when some Cow Pots I was trying got fungus. Plants haven't died and vendor says fungus on outside of pots is "normal".

Should have gotten fan and used it past 2 months.

First time starting seeds indoors and was so overwhelmed with watching them all the time and moving things on/off hat mat, rotating things under lights that were going 24/7 and checking moisture. It really was like having hundreds of infants to look after.

The article is facinating and when I start seeds indoors again I'll heed the information.

I'm growing all ornamentals and I don't think I've gotten seedlings farther along than if I'd winter/spring sowed them outside as temps permitted. I naively thought starting first year blooming perennials indoors would produce "a plant" but the reality is they're still seedlings and need different care than if started outdoors.

I did run my hand over seedlings but not nearly enough. I could smell a wonderful scent from things like Thyme, Sage and "hummingbird mint".

I think I'm going to have to continue lugging all those trays of 5" pots for another couple of weeks. Sigh.

If if could put them all outside in a cold frame now, keep it vented as temps rise and shaded with row cover cloth and have them make it with enough strength to resist diseases, etc. I'd do it in a nanosecond.

But then I reread that great article and know there's no sense in taking shortcuts.

My sciatica wishes I'd found this article in March...LOL.

Thanks for posting this on the Seed Starting forum.

I am here to testify from personal experience that improper implementation of practical aids to process of Thigmomorphogenesis produces weak plants.

I have some plants that I've planted out. Is this weakness irreversible?

Would I have a better chance of improving their "quality of life" if I took them out of the garden, pot them up in appropriate size container for remainder of season and then replant in Fall?

If seedlings grown indoors and probably not hardened off properly for long enough are doomed to a shortlived weak existence I can also start more from seed outdoors NOW and plant out in Fall.

Which option would those who understand the particular practices which promote Thigmomorphogenesis recommend for these weak plants?

Thanks in advance for any informed advice...it's greatly appreciated for a few of the more precious (to me) perennials I started indoors.