Probably it is not the right time to start/grow lemon grass in zone 5. LG needs warm/hot weather. I grew lots of them by rooting lemon grass that I bought from Asian market. I am in zone 8(GA) and probably they will overwinter here. I am not worried about that since I can do the same thing next year. My one year old LG never flowered.
SO, if I were you I will get some LG stalks, root them (in water or sandy soil next spring. If you plant just one stalk, it will multiply to 10 maybe more.

I think all lemon Grasses are organic, anyway. They are native to souteast Asia

Thank you cyrus,
I will look in the Asian market this spring.
cAROL

Carol,
Asian markets sell them wrapped in clear wrap to preven from drying. CHOOSE THE ONES THAT HAVE GOOD SOLID ROOT CLUMPS AT THE END. If they cut the buttom too much, it may not root. Also cut the tips, so that you will have abot 7-8" left. They are very easy to grow if you get the right one, as I said above. Star a month before you last frost date. If you get them rooted sooner, plant them in a pot temporarily.
ALSO: they love lots of water. I planted some in a great big pot(with a tray mostly full of water) and watered it more often than the ones in the garden. They got much bigger. Probably, LG will not overwinter in zone 5, but not to worry, you can root and plant every year. or you may try bringing the plant inside(garage), cutting it back and just keeping it slightly moist. Soon as danger of frost is over, take it outside, plant it in the garden.
I was in PIKE nursery the other day, they had LG plants. I think some better nurseries have started carrying LG plants. Even some traditional American supermarkets sometimes sell lemon Grass.