1st taste of sunlight

[Jetstar]

Sunshine coming through the kitchen window this morning and then it hit me! I went to the spare room and grabbed both the tomato & pepper started seedlings and gave them both there first dose of sunlight. After 1/2hr. I returned them to the grow box, I know I need to keep the exposure to the sun short til they grow more can seedlings be exposed to sunlight every day as long as I keep the exposure 1/2hr or less? And when do you recommend I leave them have longer sessions in the sun?

[eyegrotom]

I am no way a expert, the way l do mine is 1/2 hour the first 2 or 3 days then I increase it by a 1/2 hour every day. Mike

[loulac]

Half an hour the first day, in the sunshine, one hour the second day, then the whole day, starting in the morning when temperature is warm enugh till shade arrives and temperature drops.

[ddsack]

If you are talking about exposure through window glass, I don't think you have to limit that at all. Outdoors is where they need gradual exposure if they are not used to it.

[Jetstar]

ddsack why would a window pane glass not work just the same as having them outside in a greenhouse or if its warm enough just placed on a outdoor table? As long as its not windy out, the reason we set them in the window or outside is to gradually get them used to the sun. I think if I let them sit all day in the window exposed to the sun new seedlings would be damaged... Right? Its why I only did 1/2hr. first time, and its why growers harden them off taking at least a week giving the plant a little more sun each day til there ready after that to be planted. If I'm wrong on this please let me know... Thanks

[ddsack]

The window glass stops the sun's UVB rays, which is what you get a sunburn from. Indoor sun's rays are just not the same intensity as outside. Hardening off takes place outdoors and includes battering by the wind, as well as some direct sun.

[loulac]

One pane of double glazed windows often has received a treatment stopping infra red and UV rays, I really don't know if ordinary glass will stop anything. An expert on the wavelenghts of light will be welcome to give his opinion. Local conditions should be taken into account : Above 3500 feet it takes time to harden tomatoes. Texan sun may be stronger than in the state of Washington...

[Jetstar]

Thanks for the answers it makes sense, as I was writing the question I thought about how reading glasses have coatings so I guess window panes must also have filters built in too.

[UFXEFU]

I expose my seedlings to the outside sun on days that temperatures are in the upper 50s. I place them where they are shielded from strong wind. The sooner you expose to sun the better.

[Nan_PA_6b]

Originally Posted by loulac

Half an hour the first day, in the sunshine, one hour the second day, then the whole day, starting in the morning when temperature is warm enugh till shade arrives and temperature drops.

Loulac, really? 1/2 hour, then one hour, then 8 hours or more?

I never understood how people could harden their plants off within a few days; I start with an hour for a few days, then 2 for a few days, then 3 for a few days, etc.

When I've gone from about 1 1/2 hours to in-ground I've gotten sunburn on the leaves. Not sure what I'm doing wrong.

Nan

[Worth1]

Originally Posted by loulac

One pane of double glazed windows often has received a treatment stopping infra red and UV rays, I really don't know if ordinary glass will stop anything. An expert on the wavelenghts of light will be welcome to give his opinion. Local conditions should be taken into account : Above 3500 feet it takes time to harden tomatoes. Texan sun may be stronger than in the state of Washington...

The higher the elevation the more UV you can get.
So if you were in Washington state on a mountain you would pick up more than where I live in Texas and get sunburned even though you were freezing cold.
I would burn to a crisp at 6000 feet along the equator.
Regular glass filters almost all UVB light but only about 25 % of UVA.

UVB is what causes sunburn.

Infra red light is what causes heat radiation and keeps us from freezing to death.

So in reality if the sun only put out these two light spectrum we would be in the dark but warm and getting sunburned.
It would be a very strange world indeed.




Worth

[loulac]

Originally Posted by Nan_PA_6b

Loulac, really? 1/2 hour, then one hour, then 8 hours or more?

I never understood how people could harden their plants off within a few days; I start with an hour for a few days, then 2 for a few days, then 3 for a few days, etc.

When I've gone from about 1 1/2 hours to in-ground I've gotten sunburn on the leaves. Not sure what I'm doing wrong.

Nan

I must say I followed the rules along many years : a gradual exposure to sunlight slowly increasing everyday till I forgot once to take inside a batch of seedlings and they didn't suffer at all. From then on I shortened that phase and now every year I stick to half an hour, 1 hour, then 10 o'clock- 6 o'clock. Local conditions, as stated by Worth, should be taken into account as well as the quality of artificial light they have received in the nursery. I suggest dark green leaves and stems are less fragile than pale leggy plants. Why not make tests with a few tomatoes you can afford loosing ? it would be a safe way to test one's environment.

All the best

[Hairy Moose Knuckles]

Mine start getting sunshine once germinated. I don't time the exposure, but I do protect from gale force winds. Tomatoes are tougher than we think. I'm not saying be stupid about it, but they really don't need babying.

[rhines81]

Originally Posted by ddsack

If you are talking about exposure through window glass, I don't think you have to limit that at all. Outdoors is where they need gradual exposure if they are not used to it.

I grow by a south facing windows after my plants are too tall for my artificial light set up and yes, they still need to be hardened off. Window sunlight does not come close to equaling outside sunlight.

Originally Posted by loulac

Half an hour the first day, in the sunshine, one hour the second day, then the whole day, starting in the morning when temperature is warm enugh till shade arrives and temperature drops.

Won't waste my time with 1/2 hour as it takes me that much time to get all of my plants outside. 2 hours a day until the weekend, then 4 hours for 2 days, then 8-10 hours a day until plant out is what I try for but Mother Nature never cooperates in the late Spring, neither does my work schedule, so these days are often spaced apart and take two weeks to complete. The 2 hour excursions are after work with the Sun to the Southwest. I try to plan so the 4 hour outings to happen on the weekend, weather permitting. If not, they get a few extra days at 2 hours before going to 8-10 hours.
I start two weeks before plant out and they get what they get.

[Worth1]

My latitude and climate doesn't lend me well to give advice to northerners and how to harden plants.