purple underside of leaf
 

New to trying to grow tomatoes from seed. Started Better Boy seeds Feb 15. Twenty three out of twenty four seeds germinated within 5 days. First repot when true leaves established & put under lights. Second repot yesterday (March 12). Didn't lose any yet. Sturdy, thick stems, dark green leaves. Undersides of leaves are purple. Is this normal or am I missing something. Thanks. Good information for those of us that are not knowledgeable in this wonderful world of tomatoes.

Undersides of leaves of tomatoes and peppers get a purple hue when temps are cool- they'll green up when taken outdoors and things heat up.

kath

It can be normal in very young seedlings but if it persists in larger transplants it is a usually an indication of Phosphorous deficiency, because of a lack of Phosphorous in the soil or the soil temperature is too low which severely limits P uptake.