"Sit.... Stay!!!" How to? And what about bath time?

So I'm trying the live plants in my aquariums thing again... (thanks, Gina!   ). But how on earth do you make the ones with roots on them stay down in the gravel? I dig out a hole/space, hold the roots down there, and backfill with gravel... but they don't always want to stay put. I'm resorting to trying to hold them down with larger stones. I can get them to stay if I do a combination of the aforementioned. But is there a trick or easier way?

And the even more perplexing and frustrating thing I have a question about is what to do with the plants when I go to vacuum the gravel. Do I have to uproot them all, move to the side, and then "re-plant" after vacuuming? I feel if I don't, I'll miss too many "dirty" areas and mulm buildup; and it's hard to vacuum around them while leaving them in place without upsetting them anyway. If I left them alone and waited long enough will the roots attach to the undergravel filter? Or do they just hang out under the rocks as a tether? Will letting them float around with the roots not "planted" kill them? What to do? I have undergravel filters and a couple of inches of pea gravel mixed with regular sized aquarium rock substrate.

The plants I gave you are good for floating. Don't worry about rooting them.

Cool... thanks!