Why does the underside of the leaves on my tomato seedlings look purple. The plants ate looking okay otherwise. Growing in 4”pots. About 3 weeks old. Using organic seed starter and grow lights about 3-4” above seedlings 12-14 hr/day. Giving Espoma “Tomato!” Liquid organic fertilizer 1:3:1. In Bay Area, CA.
by GreatGubbins1943
6 Comments
50 degrees or less makes leaves cold stressed.
Because some tomato varieties grows purple under leaves
Normal.
What are you feeding them with?
Just checked all of my tomato seedlings, and there is a hint of purple under 70% of the leaves.
I think it’s normal and a perk with a lot of varieties when they are young. Don’t try to correct it, in fact, at this age, I think soil temp and water are the only two things that someone should worry about. Seed starter is already quite nutritious and Tomato seedlings can grow to this size in straight up sterile peat moss without showing signs of deficiency.
And make sure that if giving liquid fertilizer, to do it at 1/4 strength.
These look mostly fine however picture 3 makes me think there could be the start of edema, it is caused by excess water/lack of air flow. You can tell it’s edema by the “thickness” or lumpiness on the underside of the leaf, also the deep purple can be normal but I have also seen it in association with cases of edema. My advice would be to add a fan to your set up if you don’t have one,
This is very common on tomato seedlings grown inside. Nothing to worry about.