What is this structure on Dendrobium speciosum?
 

I got this Dendrobium speciosum last year and it had basically no roots. Now it has roots galore and a huge new pseudobulb with this little brown structure/leaf in between the top leaves. I don’t think it’s a spike but was curious what it is.

That's a flower sheath. A spike would come from that. It's late in the year for spike formation, so it probably won't happen this year. But it is possible the plant would flower from that sheath in years to come.

oh cool! I wasn't expecting it to bloom at all this year because it had to grow all new roots and it started this new growth over winter. If no flowers result from the sheath I won't be disappointed. I am pretty proud how big and thick this new pseudobulb is, not to mention all the healthy roots everywhere so I'm satisfied with that. :biggrin:

I wouldn't expect it to bloom this year, but it looks like it might be getting ready to be "blooming size" next year.

This new pseudobulb is twice the height and twice the thickness of the previous pseudobulb (there are about six older ones) so I’m pretty proud of it! I hope I’ll get blooms next year. This was the only one that came with dead roots from my order from Equagenera, the pseudobulbs got so shriveled and pleated so I’m very happy it’s got roots filling the pot now. The older pseudobulbs did plump up again pretty well with only a little bit of shriveling left. 👍

Den speciosums grow slowly, but they're tough! Those big pseudobulbs give it plenty of reserves to get through a "dry spell". I don't dry mine out in winter - they are outside, and even if I wanted to move them they're too big and heavy. And they bloom well. They also don't particularly seem to need repotting... when the pot gets too tight they just do "birds nest" roots. After all, they are pretty much lithophytes (" rock lillies") rather than epiphytes. They root down into the cracks to get moisture and anchor themselves, but there's not a lot of room down there so the "birds nest" roots collect detritus which turns into nutrients.