well its been well over a week for me. i have some buried, partly buried and not at all. maybe my lighting is going on me. i do have other live plants though.
I bought four for my pond. The lillies sprouted real good and growing real fast. The other two haven't done a thing. I'm starting to think it's a 50/50 chance with bulbs from Walmart. I'm not sure though.
A note about burying them - the problem is that you might bury it with the growing point downwards, and in that case the new shoots might not make their way up and out of the gravel. I would leave them laying on top of the gravel till they sprout, then turn them the right side up and bury only the bottom half or so.
Then again, I bought an A. ulvaceus with full leaves, and I could tell that it was grown upside down because all the leaves came out the "bottom" and curved around the bulb and then vertically upwards. Also, the roots will come out of the same point as the leaves (at least in A. ulvaceus) - you should still leave it with the leaves on top, because the roots will find their way into the groud. To see what I mean, look here: http://aquaplants.web1000.com/aulvaceus12.jpg