Spring is on its way and I've got my seeds planted in a little greenhouse in my garden shed. The seeds have sprouted quickly and seem to be growing long and gangly... what do I do to prevent them from getting to long and not filling out? I had this problem last year and lost most of them, and the ones that survived didn't flourish at all, they became long, stalky plants with almost no flowers. They're at the stage now with two little leaves. I've planted zinnias, black eyed susans, and miscellaneous seeds... Thanks in advance!