As far as I can tell, it just adds water cane that appears on the planet that can give you wood. Are you supposed to be able to cultivate it somehow? I'm playing with the stellar horizons mod pack, and I think this came with it

You can plant it with the agricultural tower. It's a source of wood for Gleba. You can remove the mod if you don't need wood on Gleba.

But plant what exactly? I can't see anything come up in factoriopedia or in the research tree, like I see water cane on the planet, I see water cane in factoriopedia but its not connected to anything else, are there supposed to be water cane seeds or something?

its possible one of my mods is overwriting it since I can also use greenhouses from what I think is muluna on this planet as a source of wood

Please load the mod alone with Space Age and see if that helps you understand. The water cane is directly re-planted into the water without any processing. 2 cut water cane can be processed to 1 wood.