Help with identification, please!

[muuku]

Hi, everyone! I have some cacti, one of which I received from a friend as a gift when it was a little 3 cm long branch. The original branch died because of the extended cold weather earlier this year, but it grew a lot of offsets. The thin cactus has four edges(?) of soft spines. The closest thing I could find online to what I have is Fairy Castle, and even that's not close. It's possible that the ones I have planted aren't old enough to identify properly, so sorry in advance! The second one is common enough and it seems to be under Mammillaria; I'd like to know what it is exactly, though.

[greenknight]

The second one is Mammillaria bocasana.

[teo]

Maybe Selenicereus validus for the first one (S. undatus is more common but it does not branch as much as a seedling)

[lynn m]

l believe it is Hylocereus costaricensis.

[muuku]

The second one is Mammillaria bocasana.

Thank you so much!

[muuku]

Maybe Selenicereus validus for the first one (S. undatus is more common but it does not branch as much as a seedling)

It's not quite round enough to be S. validus I think... I looked up what S. undatus was and turns out it's a dragon fruit plant! I actually have a large one out front that's already borne fruit, but I didn't think that this was what its seedlings looked like. Thank you for the help!

[muuku]

l believe it is Hylocereus costaricensis.

I think you're right! Pictures of seedlings for this dragon fruit plant look a lot like my cacti, so I'm hoping that these will grow to have flowers eventually. Thank you for the identification help.

[Gymnocal]

I have a H. undulatus seedling that look exactly like the first one, branches out similar too.