If you are still debating wether to use round-up or any other herbicide, here is some help, I hope. Round-up (glysophsate) is a non-selective systemic herbicide meaning that it will kill any plant cells it comes in contact with. It messes with cell division and will take several days (3-7) to see any signs of it working. Once applied the plant will absorb and translocate it though out the entire plant, killing the whole plant, roots and all, slowly. Did I say slowly. It works better on monocots (grasses, corn, wheat, etc. and of course orchids) than on dicots (broadleaf weeds, dandelions, clovers, tree seedling, etc.). The good thing (if there can be) with round-up is that it will not move though the medium. Organic matter binds the molecules of round-up tightly and will not let them move, even when watered. This is why you can spray round-up on weeds and grasses around the roots of desirable plants without it killing the desriable plants, but killing the weeds and grasses. With ferns and mosses they are in their own family nether monocots or dicots, so this gets trickier. Round-up is one of the only herbicides to be labaled for ferns, not mosses. So you are limited in what you can use to control ferns. Most of the time, people are trying to keep the ferns and get rid of the other plants. Mosses you will have to go into the algaecides for control. Back to your fern issues, if you use round-up be very careful that you do not get any on the orchid. I would aire on the side of caution and paint only the portion of the fern away from the orchid being very careful not to get any round-up on your orchid and wait a week and do it again, you will probably have to do this anyway as new fern leaves continue to emerge or it does not kill it. This will not be a quick fix, if you need a quick fix pull the fern out and get all of the rhizome out or repot it. As for other weeds that we get in our orchids, oxalis (small heart shaped leaves with yellow flowers), clovers, spurge, plantian, etc. common broadleaf weeds (dicots) you can use any of the herbcides labeled for 'broadleaf weeds' the 2,4Ds, weed-b-gone, lawn weed killer, the list goes on, as these types of herbicides, are selective, and will kill only dicots, and fore the most part, will not harm orchids. I hope this helps and gives you some confidence to go forward which ever direction you chose. Good luck, ferns and mosses are always hard, if you want them you cannot get them to grow and if you don't want them they grow like crazy. Act like you want this little fern to grow and it will probably die next week

If you seriously want to be a fern murderer, just keep picking off the leaves. After all the trouble you've gone through for that tiny pseudobulb, and all the questions you've posted here, why risk using Roundup? Didn't your mom buy that for you? You can't take any risks with that plant.

I hardly find ferns to be that invasive... I mean maybe if i had a green house and the spores go everywhere and i have so many plants I can't get to a hundred plants...

I really think you can just pull out as much as you can of rhizome and when it grows back pull out some more... it's hardly something that can take over. or when it comes time to replant which is better when new growth is mature enough, probably in spring, then you can remove fern and rhizome completely then.

furthermore should it get dry and you miss a watering, the orchid can remain and that thing will dessicate away...

I've made up my find already.
Like Estación said this was a gift from my mother. Plus, it's a new genera to me and I'd like to try it (and I'm really motivated because it's growing really well).
And I've been reading a lot about it. I have it for less than a year, it never bloomed and I'm already an expert on the subject.:rofl:

Considering both scenarios, Roundup or repot in Spring, if something goes wrong with the Roundup the result is inevitably the death of the orchid. And it has all the ingredients to go wrong: the fern is growing on top of the orchid's leaves and it's small, which means a slightly incorrect movement, or a small drip and the orchid leaves will be painted as well.

In the case of repot, I might risk damaging some orchid roots when removing the fern but the Stan is growing so well thatI believe it will have a lot of spare roots. And by it's growing rate, it might have a lot of energy to keep growing if any roots gets damaged.

So, I decided to repot in Spring and keep cutting the fern's leaves. In fact I've done it already this afternoon.

As you've might understand already this thread will have updates.;)

Thanks for your help in my decision.

This was a tough one!:whew
Let's hope for the best.

Good luck! In the end I think you've taken the safest, and likely best, path. Keep us posted....