My Sad, Purple Tomato Seedlings

For the past two weeks I've been staring at my tomato seedlings with absolute dread.  They haven't been growing.  Sure, they had gotten their first true leaves, and the stems were reasonably strong due to the fact that I'd blow on them every day (breeze simulation), but they were still only about two inches tall.

Not only that, but the leaves were turning purple.  From what I've been able to discover, this is probably due to a deficiency in Phosphorus or Magnesium.  Of course, there could also be too much calcium in the soil.  As if that's not enough to cause me a headache, ammonium poisoning is another possibility when dealing with purple tomato leaves.

It's enough to make your head explode!

Fortunately, I was able to eliminate ammonium poisoning.  This is mainly caused in soils that are under 55 degrees that have been well fertilized.  Cold soils are far less Phosphorous rich, so the ammonium caused by Nitrogen fertilization can spike out of control due to the lack of balance.  My seedlings were in an environment that was definitely above 55 degrees, and I haven't used fertilizer, so I can chuck this cause out the window.

I was down to either

a) Phosphorous or Magnesium deficiency, or

b) Calcium overload.

Basically, what's happening is that I'm getting a huge buildup of anthocyanin.  Anthocyanin is basically the red pigmentation that you find in plants, and purple is derived from red.  This should be a good thing.  Anthocyanin, after all, is linked to protection against several different types of cancers in humans.  Our bodies like this stuff!  Unfortunately, too much of good thing is, well, bad.  Too much anthocyanin in tomato plants is an indicator of an imbalance of the soil, and imbalances mean trouble.

Further research showed me that I didn't have a problem with Phosphorous or Magnesium deficiencies.  If this sort of deficiency is present in a tomato plant, only the edges of the leaves would be purple.  Since what I was seeing was an entirely purple leaf, I was able to rule out that possibility.

That leaves me with a Calcium overload in the soil.  Too much Calcium can actually block the plant from taking in any Magnesium or Phosphorus.  Because these nutrients are totally blocked, the entire leaf  turns purple, since no Magnesium or Phosphorous is getting through, therefore even worse than a deficiency.

In my case, Calcium buildup is very likely.  I water using the tap.  We've all seen just how much calcium buildup can occur through this - just look at all those CLR and Oxyclean commercials!

That makes it an easy fix, though.  Time for an outside transplant!  Sure, it's still too cold for outside tomato planting, but that's what I have my halved milk jugs for, after all.  They'll help keep the soil heated.  The addition of soil will theoretically reduce the Calcium buildup problem, and rainwater will help with that, as well.  Of course, this is all theory, though, and as my husband likes to say,

"I'd like to live in Theory... everything works there."