Killing an invasive plant by cutting its leaves
 

Do you think this is a good way?
In my view, as soon as a new leaf starts to grow, if I cut it the plant will consume it's energy reserves on a new growth. By cutting this new growth, even more reserves will be consumed...and the cycle goes on until the reserves are not enough for the plant to survive.

Am I thinking correctly?

If you can cut the leaves and cover the stem, maybe. Some plants are so vigorous that they can keep trying for many, many years. It depends on how vigorous the root system is.

I'm talking about a fern. It's still small, the biggest leaf is aprox. 2 inch tall.

I have been trying to get rid of fern on a couple of my terrarium mounts and they keep returning...ongoing battle. With a few of them, the plants are so delicate (i.e. Lepanthopsis astrophora 'Stalky') that it is pretty risky to pull the fern out, roots and all.

Interestingly, an article in the December, 2016, issue of Orchids (by Sue Bottom, Ferns, Weeds and Orchids. Oh My! pp. 910-913) addresses the issue.

One method mentioned in it, which I've used, is to gently brush the invasive plant's leaves with a systemic herbicide. The author's complaint about this was that with the brush she used the herbicide didn't stick well to the leaves. I've used cotton pads as applicators and it's stuck just fine. As I brushed each fern's leaf I had a finger under the leaf so the mixture would really wet the whole leaf surface. You want to do the application when the orchid's potting media is fairly moist so the plant won't need watering for a few days, which allows the herbicide to get to the invader's root system before traces of it are washed away with watering. I used this method several years ago when I received a box of Phals that all had teeny, and not established, ferns about as you describe; using Roundup, and it killed the ferns without bothering the orchids at all. If I remember right I mixed it 25% Roundup to 75% water, but the article cites using a 50-50 mix. Perhaps it was effective for me at the mix I used because the cotton pad was a better applicator than her brush?

The article mentions several other methods, using diluted herbicide sprayed carefully onto the invaders, but that's even scarier that saying "Roundup" and "orchid" in the same sentence. Bottom's overall conclusion was that, at least once the weeds are large and established, the fern's rizome will likely be too large and the only solution at that point is to repot the orchid, carefully removing all traces of fern or weed when doing so. About all you need to do is miss a cell of the fern's root and it'll come back.

Q-tip and Roundup herbicide. Dab carefully, avoiding all contact why the orchid.

Thanks for the tips. I'm not sure if I'll try the chemical way because of one thing for which I need your advise: the orchid needs reppoting into a basket so I could take care of two issues at once.
I'm just not sure if it's the best time to do it.

It's a young stanhopea wardii, potted as two pbulbs in the beginning of May and is now growing vigorously... as well as the fern.:((
Do you think I can repot it now or is it too soon?

Here are some photos of both plants:

Friends, hopefully not forever.:lol:

http://i1343.photobucket.com/albums/...pskpfmjdsu.jpg

Vigurous root growth

http://i1343.photobucket.com/albums/...psapr0og4c.jpg
http://i1343.photobucket.com/albums/...psbwk6qjmz.jpg
http://i1343.photobucket.com/albums/...psyrrmijth.jpg

Roots growing under the pot

http://i1343.photobucket.com/albums/...pse2frwj0d.jpg

Probably this one.

In the meanwhile my father in law got me some Roundup, enough for 10 L of water.
But I'd still prefer to repot it if you think is ok.

I would not repot going into the winter, unless forced to by decomposing medium.

And when "painting" with Roundup? One leaf is enough? Or should I paint as much as possible? I want to minimize the max the use of this product.