help with annual grasses

This is a 2 part question on annual grasses. Last year I planted several. Before the weather turned cold in the Fall I dug them with the intention of wintering them over in the basement under lights. They did fine for awhile, then began a slow decline and most died. The rest barely survived The temp in the basement is around 50 over winter. Perhaps I stuffed them in too small of a pot. At any rate, I'd dearly love any advice anyone has to share.
The other part of the question is.... assuming I can winter them over this year, when would be the best time to divide them?

Hi ghopper, The problem with the annual grasses is that most are, well, annual.

True annual plants complete their life cycle in one year, generally dying after they make seeds. Many grasses live this way, but not all. You can't keep real annual grasses alive for the next year.
Some plants we call annuals are really perennial (live for many years, dying back to the roots each winter), but we call them annual because they never come back because you live where it gets too cold (like MN). These you can overwinter in your basement.
Some plants we call annuals are really tropical perennial plants, like tomatoes or petunias. They are annuals in MN, but you could overwinter them under lights in your basement, if it is not too cold down there, and you have enough lights.

If you recall what species you have, we may be able to help with better advice-did you save the label? If you like a true annual grass, often they grow great from seed, and you have lights for starting them in the spring.