Thanks for the comments Rina, I do have heat in the green house. Two days ago it was 36 degrees f and very sunny, and reached 102f in the green house. Kinda scares me.

Yes, that is quite hot :), you don't want to cook young plants. It probably gets hotter as spring is getting closer. Hopefully you can control temps in GH?- have fans and/or window to open? (Photos of Grandio GH all show windows, hopefully they are on automatic hinges - if not, I would buy them & replace). Or shade cloth? If so, I think you can grow plants in there quite well. They will need some potting up, especially tomatoes, but they need to be potted up usually anyway. I grow quite a few (tomatoes, peppers) in containers and they are potted up at least 3x before ending up in final container. I wouldn't worry much about roots growing from the bottom - if they do, it is probably time to up-pot, and I also trim roots slightly/as necessary when potting up). Tomato roots are more extensive, but some pruning of them doesn't hurt plants.

Thanks Rina Greenhouse does have auto roof vents, I haven't installed them yet. Didn't feel the need through winter. But will put them on before plants go in. Also need to get a thermostat to run my fan. Do you use pots or bags? Any preference. I farm 1200 acres of corn and soybeans down here in Iowa and am more excited about my little greenhouse than my regular farming. We have always had a large veg. garden, and lots of flower beds, but not much experience at starting from seed.

I use just ordinary plastic pots, all being used over and over again :) I never tried grow bags or anything else. Have only small garden, wish I had acreage! I like tomatoes a lot, and even when I had much smaller garden grew many of them - usually around 50-60 plants started from seed, as I am always eager to taste something new.

These peppers were still potted up - I was late last summer (had to go away for 3weeks of 'prime time'), but the harvest was quite good:

I grew few indeterminate tomatoes in pots, but they grow too tall:

Here are some determinate:
If I had a heated greenhouse, I would be starting now...can't wait for home-grown tomatoes, lol.

harrison county, you can start peppers now from seed, but wait a few weeks on tomatoes here in iowa. i know you have a GH but wait a little longer, peppers take much longer to germinate, by the time you get the peppers sprouted, you can turn to tomatoes … here in the hawkeye state ...

dave

Thanks everyone, Will start a few peppers now, and try to be patient on tomatoes. Also no pine bark fines, So I think my container mix will be Coir, Compost & either perlite, vermiculite, or sand, maybe a combo of those three.

al's 511 is great for container tomatoes. just make sure you use a large enough container … no 5 gal buckets. i like the container cattle minerals come in … now peppers are fine in 5 gal buckets, at least for me, just don't set them on the ground or they will wick ...

DSM5 are there pine bark fines in Des Moines, my daughter lives in west D M and I go to the Woodsmith store often.

yeah, lowes has something that needs to be sieved and separated (purple bag) … i run it thru my chipper blower and sieve it into a wheelbarrow. if you are making gritty mix, use no. 2 cherrystone, found at farm and home stores, and napa floor dry, part no. 8822. i pre mix those 1:1 and then add pine bark, which is usually reptibark from the pet store.

if you are making the 511 mix, make sure you include the perlite. read any of al's soil movement and water retention treatises ….

like this one

We are in the same zone well 5b here. What have the current night temps been at in your heated GH? It's a great idea starting them indoors now but you'll want to move them out within 3 to 4 weeks as it will be starting to warm up in the GH. For venting on sunny days in spring I just leave the door open a crack. This usually keeps the temp around 70-80F and that's only in March! April starts to get hot and so on. For many who have a GH it's avery different climate then what we're use to.