Brassia, is this a spike or a new pseudobulb?
 

My brassia eternal wind hybrid has new growth but i've not sure what it is, can anyone help me?

if i was to cut off my brassias back bulb will it survive? (just wondering)

also in the last picture is that a pseudobulb covered in growing leaves or is it some sort of spike?

That's definitely a new pseudobulb. A spike would be much, much thinner, and come from the side of a pbulb, instead of in front of it.

As for whether or not your back bulb would live, I can't say for sure. Personally, I wouldn't risk it. Cutting it off would take food from the new growth, and could possibly lead to that new pbulb being aborted.

-Tim

My experience with brassias and oncidiums in general is pretty limited but usually the spikes come from between the leaves that come out of the pseudobulbs.
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