Beginner Gardening: Beefsteak tomatoe leaves undersides are purple?!, 1 by Gymgirl

Gymgirl wrote:
Googlie,
You know how human babies turn blue when they're cold? Guess what color tomato babies turn when they're too cold and damp?

Only because I just experienced this in January with some of the 208 seedlings I started.

Heat is necessary for germinating the seeds. However, once they're up, a cooler temp will slow them down so they can get nice and fat. But, you've got to control how damp you're keeping them in the cool. That purple is a signal they are not happy in the growing conditIons.

So. I recommend you dry the seedlings out a bit. Then, check that windowsill for a draft, which could be a contributing factor.

See if this helps, and keep me posted on your progress. Here's a pic of my purple babies.

Linda