It is going to be warm this week. I have a flat of tomato seedlings that are about 2" tall indoors under lights in the basement. Can I set the flats out for a couple of hours on these warm, sunny days?
For what purpose? Are you familiar with the process of hardening-off plants before making changes in their environment? If not then you need to do some research into the process.
Moving young seedlings from the protected environment of indoors under lights to the outdoors into the sunshine can easily and quickly kill the plants if not done properly. At the very least it is very stressful for the plants. Then moving them back indoors again is more stress.
Once the plants are of a size to be ready for the garden and approximately 7-10 days before you will be transplanting them to the garden, THEN slowly begin the process of hardening them off with the goal of adapting them to their new and permanent environment.
I routinely move my tomato seedlings in and out because I don't have a good lighting system inside. I do have to be careful so they don't get sunburnt or windburnt. If you have an outdoor spot with filtered sun or bright shade that might be best, just for a few hours at first, and keeping an eye on them.
I have a hoop frame that I just built. Is it possible to just start some seeds in this? Here in the Ohio Valley it can be 70 one day and 32 the next. If I open both ends of the hoop frame will that be enough ventilation?
probably not, especially this year. I would keep them indoors in a warm spot until they germinate. I know there are different ideas on this but last year I moved plants out into a small greenhouse as soon as they germinated. It was a cool spring but I adjusted the amount of outside air according to the foercast for the day. I moved them in at night when temps dipped below 45 and out the next morning. A few days I left them inside all day. It takes a lot of attention to detail but it worked out very well. This year has me a little worried about doing that but I am going to start seed in about a week and see how it goes. As far as moving them into the hoop after they are up I think it's doable but you need to get them out as soon as they are up and monitor the weather closely for temp, clouds, sun and wind. One thing I had going in my favor was a shade cloth on the little green house and you probably won't have that with the hoop.
Can You Start Seeds In a Hoop House ?
The answer, I think, is "YES" but it depends on the soil temperature rather than air temperature. Tomato seeds (and many other) need warm soil to germinate. Probably 60F is about the minimum. 75 -80 is ideal. I doubt that your soil temperature will get that hot under the hoop( considering the calendar and your zone). UNLESS you leave it on the garden bed for several sunny days. Anyway, it will take twice as long, even longer, in cooler soil for the seeds to germinate
This post was edited by seysonn on Mon, Mar 10, 14 at 3:47
We had a warm spell right after my seeds germinated, and I put them outside during the day right away. I watched them carefully to make sure they didn't dry out.
I don't think it's a good idea to go from indoors to outdoors that fast once they get true leaves. I plan to start planting this week, and I'm still moving some of the plants in at night and out all day in full sun.