Skabooya is right, but to add a little more detail, and make it seem more complicated: Use long tweezers, like the 12 inch long ones. Grab the base of the stem with the tweezers. Poke them down to the bottom glass through all layers of substrate, if you have layers. Slightly loosen the tweezers, wiggle them slightly as you open them a bit more. Then pull the tweezers out. Drink no more than one swallow of your favorite beer. Pick up another stem, and repeat above, but about an inch away from the last one. If you have more than 100 stems to plant, substitute a non-alcoholic beverage for the beer after the first 20.
I recommend that you print this and keep it where you can always find it.
I have tried to follow and still find it difficult to plant the soft stem plants like the rotala and also hair grass and the kinds. I use ADA Amazonia II and the moment I lift the tweezer up, the plant wants to come out too. Some suggest that you plant 2 or 3 stems together, what do you suggest?
2 or 3 together works too but then you will need to worry about light not getting to the leaves where its all scrunched up. Personally i do grab a bunch and then shove into substrate.
Plant them deeper or what you put under the substrate plant on a slant so more stem is covered with the substrate and then the stem is not directly up and down out of the substrate. The substrate will weigh the stem down more if planted on an angle and if more stem is shoved under the substrate.
Planting at an angle does help a lot, as does not having an extremely light weight substrate. I know when I do this it sometimes works perfectly, other times I struggle to keep the plants from following the tweezers out of the substrate. I'm never exactly sure what I do differently when it works so well, but I suspect it is the angle. And, I never plant more than a single one at a time - if I am going to all of the trouble of separating them I figure taking the next step of planting single plants is only a small increase in the work.
That only works with stem plants like roses for you lover.
Vaughn is right. Leave the leafs on. It allows for more surface area to hold the plant down under the substrate. They will just rot away afterwards anyway once the roots form so no worries.
IMO/IME stripping the lower nodes of leaves gives the following benefits:
1. Leaves will not rot under the substrate. Leaks nh4 and will help clog the filter.
2. Light will penetrate easier to the inside of the plants. This results in thicker bushier growth.
3. With the lower stems bare it is easier to plant stems SINGLY and allow better spacing.
4. The longer bare stem can be pushed deeper in the substrate. They soon will get taller
Drawbacks are more planting work (a little and so what?) and time but it will be worth the effort. If we are doing the right things the plants will soon fill out and grow, no?
Planting several stems together is 'easier' and looks nice initially, but trimming the plants as they grow in will give the same effect and also allow you to control this growth. Observation is easier as you have seen it grow.......
The plants will be healthier and look better and should have a whorl of leaves close to the substrate as it grows. If this does not occur, then they are too close together or too thick and need trimmng..
You can always loosen the substrate first with your finger to help.
Remember too that stems are bouyant and want to float. The taller/more leaves, the harder to keep in place initially. Less height/leaves will help this at first.