Is that a pup off to the left?

Yep, I have another which has made a few pups. Very slow initially.

Is that a non-mutated pachycereus schotti behind it?

Yep, good eye, it is in too much shade from a leftover Palo Verde stump that I let get too bushy (> 6 feet tall) every summer.

I got two big cuttings from the Desert Botanical Garden in Phoenix a bunch of years back that I eventually put in the ground and while not off to the races, the difference in growth rate between in the ground and in pot is pretty amazing.
My other one is starting to develop the characteristic 'hairy'-looking tip on one of its arms.

They are pretty much bullet proof here as long as they are not overwatered too much.

I have seedlings from it (koehres) and i also have a beef with that plant(not literally). I find it quite weird with the spines. On the photos ive seen ,at first its all neat looking like euphorbia canariensis. Then im guessing as it ages its gets those crazy spine crowns like youve mentioned. Are they supposed to be cephaliums or something? Either way, i cant seem figure out why this plant decides to go from fairly cute to pain train when it reaches a certain age /size?
https://upload.wikimedia.org/w...

Almost all big ones of a certain size/age appear to get it, not sure why. I suspect something to do with flowering though both mine and a previous one that I gave away have flowered well before ever developing any signs of those 'hairy' tips. Of course they were all large cuttings from presumably mature DBG collection plants, so those plants would probably be of flowering age.

However, all my plants have developed flowers very low on the arms that would be well away from where you might expect those 'hairy' tips to develop. I have wondered if it could be to do with sun protection, but I am not sure if that makes a lot of sense.

Well, that data actually disproves my hypothesis. Youd think that spikes would be some kind of fruit protection, but nope. They are certainly not there to ward of predators, because the sensible thing would be to actually have the lower and younger part of the stem guarded, while the fruiting and blooming parts are left exposed like on saguaro or cardoon.
Is this plant pollinated by bats or something else? What animal eats the fruit?

It is a night bloomer and I suspect it to be some kind of moth, but bats would be possible too. I do not know what eats the fruit, mine have not ever set fruit, nor do I remember ever seeing them on the big plants in the DBG. Suggesting that it might be a pretty specific pollinator, which does not occur here in the Phoenix area, which is outside of the plant's natural range.

According to my BC Plant Field Guide, the spiny part at the end of the stems (pseudocephalium) is an indicator of sexual maturity because all of the flowers and fruits appear in this area.

Apparently not all, as Thijs has observed.



The pollinators in habitat are supposed to be bats and insects.

There is a dedicated pollinator called the senita moth (Upiga virescens) in the Sonoran Desert which may account for 75-90% of the pollination, depending on the year and location. This mutualistic situation is somewhat similar to the yucca's relationship with the yucca moth.

More info here.

https://www.ncbi.nlm.nih.gov/p...

The fruit has also been eaten by humans, but is not supposed to be particularly delicious compared to other cactus fruit in the area, like Stenocereus thurberi.