Polycarbonate greenhouse - hardening off necessary?
 

I'm wondering how much I need to harden off plants before I move them from under lights in the house to the greenhouse. The greenhouse has two layers of 8 mm double wall polycarbonate panels, so nearly all UV is blocked. I can heat up the room in the house to approximate the temperature in the greenhouse the last few days before I move them. Do they need hardening off for sunlight minus UV?

Steve

I have never hardened off from grow lights to the greenhouse.

I don't harden off, but I move seedling trays out as soon as practical, preferably while they still only have their cots. The sooner they get real sunlight, the stockier and healthier they are. I carry them back in at night or when the temps drop below 55 or so, until I begin to heat my greenhouse at night. This year the hill to my greenhouse has been snow covered and slippery, so I have not yet started my twice a day shuffle. I think there is a possibility of some sun bleaching on older leafed out seedlings if they are out for the first time, but they will grow out of it fast. I use sunscreen on myself when working in the greenhouse for many sunny hours, because I have gotten burned through my double wall polycarbonate.

You can damage indoor grown plants if your greenhouse is too warm + a lot of sun. The indoor root system can't supply sufficient moisture. But if you control those issues, all should be fine.
GG

It has a lot to do with.
Time of year.
Latitude.
Altitude.

They will adjust without burning but put them in on a cloudy day or in the evening allows them to adjust gradually rather than straight into bright sun in there. Is it twin wall?
KarenO

Thanks!
 

Thanks everyone for the replies. It's good to know I don't have to cart them in and out.

ddsack, your point about the benefit of real sunlight is a good one. If only we didn't still have 2 feet of snow and low temps...

KarenO, it's "double twinwall" - I decided to heat the greenhouse to get an earlier start on May 1st, so I added a second layer of 8 mm twinwall using silicone. (By the way, Karen, my KARMA pinks are doing great! I'll post photos when they are in the greenhouse. I sowed more plants for outdoors, including giveaways, yesterday.

Steve

[QUOTE=sjamesNorway;694126]Thanks everyone for the replies. It's good to know I don't have to cart them in and out.

ddsack, your point about the benefit of real sunlight is a good one. If only we didn't still have 2 feet of snow and low temps...

KarenO, it's "double twinwall" - I decided to heat the greenhouse to get an earlier start on May 1st, so I added a second layer of 8 mm twinwall using silicone. (By the way, Karen, my KARMA pinks are doing great! I'll post photos when they are in the greenhouse. I sowed more plants for outdoors, including giveaways, yesterday.

Steve[/QUOTE]
They will be fine in a twin wall straight out.
Happy to hear your KARMA pinks are doing well , excited to see your greenhouse pics when you post them
KarenO