My Purple Tomato Seedlings – Feed Me!

It’s time for a confession – I can sometimes be obsessed with words and their usage. This is especially the case when it comes to plants. If I hear someone say “the plant needs a drink,” I can feel my back tightening up! Plants can’t drink; they absorb water through osmosis and hydrate. Like I said, I can get a little obsessive about word usages.

Because of this tendency, I also don’t like phrases like “plant food” and “feeding your plants.” I hear the word “food” and I think of eating – plants don’t eat. Plants take up needed nutrients and minerals and through the process of photosynthesis make their own “food,” or what I’d prefer to call photosynthate!

But one of the dictionary definitions of “feed” does make sense when it comes to plants – “to furnish something essential to the development, sustenance, maintenance, or operation of.” I guess you can “feed” a plant.

I write all of this because of something that recently happened with my tray of tomato seedlings. I noticed that one side of the tray was green and growing well while the other side had plants that were smaller with a purple tint to the leaves and stems. It looked like there were two different varieties of tomato in the tray but that wasn’t the case – they were all the same variety.

Tomato Seedlings - note the smaller, purple plants on the left.

Tomato Seedlings – note the smaller, purple plants on the left.

Phosphorus deficiency can often lead to plants that have a purple color in the stems and leaves. But why would half of the tray be OK while the other half was suffering from a deficiency of this nutrient?

I thought back on what I had done to this tray of tomatoes and it all started to become clear. The potting mix that I like to use is a local gardening center’s own formula. I’ve found that plants grow well in it but it doesn’t have any added fertilizer. I had started the seeds of the tomatoes in this mix and I had used this mix when I transplanted the seedlings into the tray. A few weeks ago I had made up some worm casting tea and poured some of it on the tomatoes. But I hadn’t poured it on the whole tray; I had added it to one side of the tray, assuming that it would infiltrate into all of the soil.

If I had added a lot of the worm casting tea to the soil, drenching the tray of seedlings, I wouldn’t have had this problem. But the mix wasn’t very wet when I added the tea so the nutrients in the liquid stayed localized. One side of the tray had plants that were growing well – you could say they were “well fed.” The other side of the tray of seedlings was starting to show signs of nutrient deficiency. The purple leaves and somewhat stunted growth was a clear signal that “something essential to their development” was missing – they weren’t being “fed.” If those tomatoes were like Audrey II from Little Shop of Horrors, they would have been crying out, “Feed me, Marc!”

So that’s what I did. I have some African Violet “Food” that has micro nutrients and a 7-7-7 N-P-K (nitrogen, phosphorus and potassium) ratio so I knew it would provide what the tomatoes needed. I added this liquid fertilizer to the entire tray of seedlings and now, only a few days later, I can see a difference. The youngest leaves on the phosphorus deficient plants are more green and less purple.

Tomato Seedlings after Adding Phosphorus

Tomato Seedlings after Adding Phosphorus

Next time I’m starting plants in this potting mix, I’m going to be more conscious about fertilizing the seedlings. I know the dangers of over-fertilizing so I tend to go to the other extreme and under-fertilize. It’s time to seek a middle ground regarding fertilizer.

The amazing thing in all of this is that the plants let me know what they needed. The purple leaves were a message delivered loudly and clearly. The message I took from those leaves was that something essential was missing from the seedlings’ soil. But maybe I can lighten up a little bit and admit what the message really was – “Feed me!”

(But if the soil ever gets dry and the plants wilt, I’ll won’t say they “need a drink” – I have my limits!)


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