Polycarbonate greenhouse - hardening off necessary?

[sjamesNorway]

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

[clkeiper]

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

[ddsack]

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.

[Greatgardens]

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

[Worth1]

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

[KarenO]

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

[sjamesNorway]

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

[KarenO]

Originally Posted by sjamesNorway

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

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