Leafy crest

Tiny leaves on a Euphorbia flanaganii crest mark new growth. Each tubercle on this plant produces one leaf.



Full photo here

I knew right away that this was yours Baja. I'm a big fan of your collection and photos!

Cool banner Baja!

Here for the curious is that same crest from the banner pic today, so you can see what it has been doing the last 2 months.



Curiouser and curiouser.

Love it!

What a neat plant. Fascinating growth habit. It's completely new to me, so thanks for sharing.

@Baja_Costero

Very cool, Baja!

This is an example of what is called "fasciation." Normally, when a new shoot is growing, the very tip of the shoot where the cells are actively dividing is like a little "point" that forms a cone and then the cone lengthens into the stem. You can see several normal stems all around the plant in your picture above. With fasciation, the "point" of dividing cells is instead a "line" of cells, and they end up forming what appears to be several stems fused together---the central structure in the image above and in the banner image.

Flower heads can be fasciated, too.

Lots of plants can develop fasciated stems or flowers, often only on occasion, but some plants commonly do. Crested celosia (cockscomb) is one many folks are familiar with:



Many things can trigger fasciation: weather, viruses, bacteria, chemicals, genetic mutation. Often the cause is unknown.

I did a little looking around for more info on fasciation for those of you interested:



Here is a good article on fasciation:
https://mastergardener.extensi...

Some good pictures of "normal" and "fasciated" Euphorbia flanaganii (also called "medusa head"
https://succulentgrowingtips.c...

A couple more fasciated plants:
https://www.canr.msu.edu/news/...

Great examples on that Euphorbia page of a so-called "arm crest" (like the one in the banner) and a "head crest" (significantly less common in cultivation) where the "medusa head" itself, not any of the serpents coming out of it, develops that characteristic line formation.

Baja, please explain "arm crest" and "head crest" a little more. In the article, they refer to "crests" and "monstrose forms." Is that what you are calling arm and head crests, respectively? They say they arise the same way.

These plants are given the common name medusa or medusa head because of the form the plant takes. It's a little like a central head (the main stem) with lots of serpents snaking around it, gorgon-like.



The term "head crest" refers specifically to the central part, the main stem from which the many narrow stems emerge. When the head crests, it causes a different effect (illustrated on that page but missing from the database) than when the snakes (or arms) crest. Those terms are meant to distinguish which part of the plant is crested (monstrose).

Usually when the head crests, only that central part displays abnormal growth (developing 2-fold symmetry around the line that makes up the growth center, like a lot of crested globose cacti) and the skinny branches coming out around it look normal. By contrast, when an arm crests (like in the picture) only that part displays abnormal growth, and it's more like a coral type pattern. People cut these mutant arms (looking more like undulating fans) and root them to have the arm crest on its own, with that fascinating coral pattern. They are quite easy to reproduce this way.



The reason arm crests are much more common than head crests is that they can be propagated easily from cuttings. The other kind has to spontaneously arise (whatever triggers cresting is beyond me), and cannot be propagated easily, to the best of my knowledge. So when people grow a lot of seedlings, they occasionally get lucky and a head crest comes out of it.

I hope that makes sense.

with @Baja_Costero
But, don't confuse Arm crests with Polytomy, they can look similar.

Baja, Yes, that makes sense. Thanks! This is a really cool looking plant. Do a lot of euphorbes do this?

@Aeonium2003

Evan, what is polytomy? When I looked it up, I read that it is a type of fasciation where the apical meristem divides into several meristems. So the difference is that the arm crest is like a line of meristematic cells, while polytomy is several points of meristmatic cells? What kind of structure does a polytomy make and how is it different from the arm crest?

lauriemorningglory said:Baja, Yes, that makes sense. Thanks! This is a really cool looking plant. Do a lot of euphorbes do this?

The most common crested Euphorbia in cultivation is probably lactea. We have a few good pics in the database of crested Euphorbias:



I don't think they do it more or less often than other succulent plants. The most common ones are probably the most stable and the least difficult.

@Lauriemorningglory
My definition of Polytomy would be a growth point with more then one crested growth points. Kind of like a Monstrose plant combined with a crested. Think of a Crested plant as a single growth point, just in a line. And Polytomy as a Plant with multiple growth points arranged in a line.
Here's a few pics (not mine) that shows multiple crested growthpoints, which is polytomy.
POLYTOMY

CRESTED

Thanks for the pictures, Baja. I don't grow houseplants, but I might have to try one of these sometime.

Evan, Yes, it does look like an arm crest but very thick, with multiple new heads along the ridge. Each head will try to grow in diameter, correct? but they will crowd each other. What happens as this structure gets bigger? Do one or two dominant heads take over and the others give up and get overgrown? Do the heads eventually fall off and start new plants?