Hardening question

[Ms. Jitomate]

I started hardening outside under shade when we were having temperatures in the 70's. After 3 days I moved them to a driveway with a canopy shade cloth. Now I have moved them to no canopy and no shade, except now there's an overcast and possible rain in the next two days. Yesterday they were out from 7:30 am to 10 PM in a partial cloudy day. The day temperatures are now going to be in the mid to high 50's and the lows in the 40's. When it rains they will be indoors again, but does this mean that when we get some sun back, I have to start hardening again?

[Crandrew]

No please dont start hardening them off again. Mostly the hardening process is for light UV not for temperature, IIRC. I am also in the middle of the same thing in OC, and will just add another day of sitting in the partial sun. These plants are very resilient and can handle the slight change.

[Hotwired]

Originally Posted by Crandrew

No please dont start hardening them off again. Mostly the hardening process is for light UV not for temperature.

Crandew is exactly right. It's 90% about UV and 10% about temperature. Think of it as getting a slow tan so you don't burn. Once you've tanned you're good to go. If you get a lot of new leaves, then they will burn, like exposing new skin. I use a plastic tent that isn't UV coated, because I always end up forgetting to move them.

Hotwired
Working Mans Guide to Hardening off Plants

[Deborah]

I didn't know that-I thought hardening off meant temps. Love this forum !

[Crandrew]

I'm going home today between work and going karting with friends...just to put the girls out. Its a commitment folks I wish i had a 10'x20' hoop house or something.

I agree Deborah, we get to learn so many great things on here.

[luke]

Originally Posted by Hotwired

Crandew is exactly right. It's 90% about UV and 10% about temperature. Think of it as getting a slow tan so you don't burn. Once you've tanned you're good to go. If you get a lot of new leaves, then they will burn, like exposing new skin. I use a plastic tent that isn't UV coated, because I always end up forgetting to move them.

Hotwired
Working Mans Guide to Hardening off Plants

I like this plan, but it fails to mention any length of time for exposure. Is this something where you leave your plants out all day for hardening?

[Hotwired]

Originally Posted by luke

I like this plan, but it fails to mention any length of time for exposure. Is this something where you leave your plants out all day for hardening?

Ouch.. forgot that, didn't I? .. Need to fix the PDF. I leave them in a hoophouse with regular plastic from Home Depot for 4 days minimum.

My hoop house is a $125 ShelterLogic Carport )Black Friday deal) with painter's plastic drop cloth. It blocks about 65% of UV, so plants get a nice gentle tan.

[Crandrew]

I have always liked your carport seedling rooms!

[Ms. Jitomate]

Hotwired, that's an awesome setup. So if it rains it doesn't matter to you because they are well protected. Meanwhile, I only have 144 plants, and I'm trying to do this without a large monetary investment.

Okay, hardening is to strengthen and to accustom the leaves to UV lights. We are getting sunny days, cloudy days, and rainy days, which means the UV range changes. Will the plants suffer a set back if they are three or two days of rain, meaning the plants are indoors? When I bring them out after two days of rain, will they be ok outside as the last day they were out? New leaves are appearing so, are they more vulnerable than the older leaves?

I’m so sorry to ask these questions. It's my first time planting tomatoes from seeds and I really want to learn.

I have the commitment because I’m at home, due to unemployment. I’m willing to move them around especially now since their size is manageable. I’ve got tables set up in sunny and shade areas. I’m willing to move them around since I want them to be strong and healthy and eventually out of my house.

[luke]

Hotwired -- Thanks for your response. I will give that a shot if I can sneak it past my lovely wife.

[Hotwired]

Originally Posted by Ms. Jitomate

We are getting sunny days, cloudy days, and rainy days, which means the UV range changes.

They will still harden in the rain. You can get sunburn on an overcast day. Several of my fishing trips drove that fact home. It's like tanning, sunscreen for a full day of sun, or a little sun each day for a week. I try to use 40 hours of sun under plastic as a rule of thumb, whether it's (5) 8-hour days or (4) 10-hour days.

Hotwired NY

[Crandrew]

Originally Posted by Hotwired

They will still harden in the rain. You can get sunburn on an overcast day. Several of my fishing trips drove that fact home. It's like tanning, sunscreen for a full day of sun, or a little sun each day for a week. I try to use 40 hours of sun under plastic as a rule of thumb, whether it's (5) 8-hour days or (4) 10-hour days.

Hotwired NY

You learn this quickly when you spend some time in the snow or skiing on an overcast day.

[bwaynef]

Originally Posted by Hotwired

Crandew is exactly right. It's 90% about UV and 10% about temperature.

So, if I'd been planning on moving my seedlings out from under lights and onto a shelf in the greenhouse that claims to block 99% UV ...I'm still going to have to harden them off later?

[Crandrew]

Yes you will. They will sun burn.

[AprilMayJune]

This thread is super helpful. I too thought a lot of the hardening process was about temps, not UV. Hardening off is basically where everything fell apart for me seedwise last year (though my plants were not in great shape to start with -- I'm a newbie and still learning) so I need all the info I can get to avoid that this year.