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[oplopanax]

Hey y'all-

I have a bunch of Trichocereus macrogonus seedling that are about 6 months old.

 They are very tiny & are all mostly reddish/purplish in color. I have not been worrying about it but it seems like they have been that way for a long time and I am becoming concerned that they are suffering deprivation of some kind.

They are in a commercial cactus potting soil, so should have some nutrients, but maybe need a little bit of a nitrogen rich fertilizer?

Any insights appreciated, please see picture below.

<3!

1 Like mj likes this.

[Auxin]

The pink/purple is a form of cactus sunscreen, its an antioxidant the seedling produces to protect against too strong of light.
You could move them a bit farther from the light, but they may just grow out of it where they are and get nice and fat.
As for ferts, they would likely enjoy monthly dosing of quarter strength general purpose 'grow' or tomato fertilizer.
Too heavy on nitrogen and they might get weak, but 15-30-15 works fine IME.

4 Likes Frog Pajamas, AcaciaAve, danzick and Toxicodendron like this.

[oplopanax]

Thank you!

That makes a lot of sense, they are getting a lot of light. I am about to rearrange things for the very early spring (I am kind of crazy I know) seed starting frenzy that will soon begin...

How about this:

One of my older seedlings is mostly brown on the bottom, from the roots to just a bit below the growing tip. It is not squishy or rotten, and it seems to grow fine, but I still worry a bit.

You can see it is one of the 2 seedlings that are planted together in one pot in the picture below.

[happyconcacti]

I'm not quite sure but it looks like it's "hardening off". No worries there.

And about purple seedlings, I know a grower that lets most of his Trich seedlings get so much light that they turn purple. He said it slows them down significantly but that they'll be fat, healthy yearlings. 

[oplopanax]

Great, this is all great news. I am so excited for the years to come when these babies will be all grown up...