When growing vegetable plants from seeds, how does one prevent them from becoming leggy (stringy)? My broccoly become very long and tall and sometimes fall over.
You need to keep a grow light or cheap florescent light over you seedlings and down close to the young seedling 3 to 4 inches above the leaves. This helps to keep them from getting leggy.
After the seedlings have come up a bit, you can direct a gentle breeze from a fan towards them. That will help as well. Air circulation is good anyway.
Devil is right...it is the light. Speaking from experience...first time I grew it from seed; they came up, then fell over. Tried again with lights right down on top of them, and all of them made it. This year; I wanted to see if broccoli and cauliflower could be 'dense planted'. I planted 300 seeds in a standard 1020, shoved it under the lights, and they ALL came up. I now have 300 broccoli and cauliflower plants all over the yard, garage, driveway, etc...
OMG.
Brassicas more than any other vegetable need light as soon as the seed bust thru the surface and throughout the whole greenhouse process or they will get leggy and ultimately just curl up and die.