What does hardening off plants mean?

kylestlJanuary 27, 2009

Someone told me to harden off my pepper plants........ but i don';t know what it means can someone tell me?

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organicpepper_grower(Nova Scotia)

grdually take you plants outside for a few hours a day until it can stay outside, basically your adjusting your plants to the outside temps and wind, etc..

    Bookmark   January 27, 2009 at 12:10PM
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spencersmom(z7B Virginia Beach)

Kyle are you in Saint Louis or does stl stand for something else? If that is where you are, your plants might not appreciate being hardened off just yet.

    Bookmark   January 27, 2009 at 1:05PM
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rdback(Z6 VA)

Hi kylestl

As organicpepper said, you need to acclimate your peppers from their indoor environment to their new outdoor environment. It's not difficult to do, but if you don't do it you run the risk of losing your plants. The link below is to a FAQ about transferring plants to the outdoors.

Enjoy and welcome to the Forum!

Here is a link that might be useful: FAQ - transplanting

    Bookmark   January 27, 2009 at 1:34PM
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no im not putting the plants outside yet there is 4 inches of snow, i was just wanting to know what it meant.
Thanks for the quick responses.

    Bookmark   January 27, 2009 at 3:04PM
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What is Snow?

    Bookmark   January 27, 2009 at 4:41PM
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habbob(San Diego)

I saw a picture of snow once.

    Bookmark   January 27, 2009 at 8:01PM
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Hardening off the plants is really just to get them used to the immense change going from Fluorescent lights to the intense light of the Sun. If you take a plant raised inside and put it directly out in the sun, you can literally watch the leaves wilt. It might be a surprise seeing how short of a time it takes to completely ruin the plant. We're talking minutes, not hours. I spend about 10 days to acclimate them to the morning sun. I don't give them any direct sunlight until it's been 5-7 days. I always plan it so that I can watch them very carefully the first 5 days.
I typically start on Wednesday. I want to be able to keep them outside when I'm home from work that weekend. I have not kept good records of my hardening off scheme. I just make sure to peek at them frequently to make sure they're ok. At the same time, I want to get them used to the life outside as fast as I can.

This should be pretty close to my hardening off schedule:
* day 1: 1 hour before sundown (in shadow)
* day 2 : 2 hours before the sundown (in shadow)
* day 3: 3 hours before sundown (in shadow)
* day 4: Saturday: Getting more aggressive. Keeping them in the shadow during the day. Plants are outside most of the day. I make sure to watch them pretty carefully since the intensity of daylight even in shadow is many times more powerful than the indoor lights.
* day 5: Sunday: Shadow most of the day, start introducing evening sun. Checking plants frequently.
* day 6-7: Monday-tuesday: Taking them out in the sun after coming home from work. Outside in shadow when I'm at work.
* day 8-9: increasing the exposure to day-light sun.
* day 10: Plants are able to tolerate morning sun as well as daylight sun. Putting the plants where they'll life the rest of the summer.

I am sure that there's going to be various opinions on what's best and how fast. But in the end, the only important factor is to ensure the plants safety so they don't experience months of setback, or in worst case dies. The more time you can spend with them during this time, the better. I am pretty sure that the ones with the most plants in this forum, will take a week off their regular work to ensure the hardening off is done right.

    Bookmark   January 28, 2009 at 1:05AM
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caroltlw(z8 n_FL)

One another thing I've noticed is that if the seedlings get very cold over night (but not freezing) they react poorly to intense morning sun, even if they've been outside for quite some time. I had to move morning-wilty plants to the shade a couple of times last year.

    Bookmark   January 29, 2009 at 11:33AM
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austinnhanasmom(5 CO)

I read this:

Hardening off time gives the plant time to thicken the stem and skin, forming a waxy surface. Chloroplasts will rearrange such that they aren't stacked as much, preventing sun burn. As new leaves develop, they'll be smaller and better adapted for direct sunlight and life outdoors.

If you regularly run a fan on the seedlings, they'll be stronger and harden off quicker as they'll be part way hardened from the fan "abuse".

    Bookmark   January 29, 2009 at 4:57PM
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I have 6 pepper plants that I took into the garage last fall before the first frost. I cut off all of the leaves and smaller branches. The plants obviously did grow any, but seem to be healthy enough to introduce back into an outdoor environment when spring comes.

Should I harden these any differently than a seedling? The main risk factor of the wind probably isn't as applicable since there is an established root system, but should I be worried about the temperature differences? Would the schedule as suggested by KJ above work for these as well?

BTW, this is my second year of gardening peppers and tomatoes and I have spent a lot of time getting information from various forums on GW. I haven't contributed a whole lot in return due to my lack of knowledge and experience, but I do owe several people on this forum a thank-you for the advice shared over the last 18 months.

    Bookmark   January 30, 2009 at 4:29PM
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smokemaster & habbob,

Not funny! Got stuck in my driveway yesterday.

WhatÂs snow? Send me a SASDT (self addressed stamped dump truck) and IÂll send you each a load! LOL

It looks like IÂm in one of those snow globe things right now but my super hots (Jolokia) starts are safe and warm on their heating mat.

Envious in Ottawa,


    Bookmark   January 30, 2009 at 6:18PM
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I have a 12 inch oscillating fan that I use on the plants a little bit every day. Just a few minutes. Others just brush the plants. It will make a big difference in the stem and root development. Last year, I grew my Hab. plants inside for 5 months. They did not notice the heavy SD winds when I finally put them outside.

The leaves created when they are inside are indeed darker and much bigger than the ones developed when they get full sun. They are remarkably good at adapting. But take those leaves straight out in the sun, and they will burn to crisp in no time at all.

I've never overwintered plants. Too many months of coldness here in SD. I don't know how much hardening off you would have to do. I suppose I would take it easy. If there are no problems then go more aggressively.

    Bookmark   January 30, 2009 at 8:09PM
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I have a question: do I need to wait until after last frost date to start hardening off or can I try and time it so that I'm done hardening off right after last frost?

    Bookmark   February 1, 2009 at 3:41PM
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austinnhanasmom(5 CO)

I would try to time it, or get it done before the last frost. A bit early is not bad because the new growth will continue with the hardened off process. Moving them back inside to protect from freezing, or near freezing temps, is necessary and ok.

    Bookmark   February 3, 2009 at 7:59PM
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