Here's what to do with it, if growing it - trim it, as if you are getting it ready to use that day. When it is that fresh, you don't have to cut it as short, but the root end keep cutting the stem shorter, until you see the purple rings, and the other end varies, depending on how thick it is. 6-8 inches long is ok, except for very small stalks. But get it as if you are getting ready to use it, then put them in a narrow foodsaver bag, and vacuum seal it. They will keep forever in the freezer this way. The last time I grew them was in '21, because it was a huge amount, on just 4 plants. And the lemongrass is still better than something I would buy. Here are some photos, showing that cutting of the stem, I described, a couple of the foodsaver bags, with 3 and 4 stalks, and a whole bunch of the foodsaver bags ready to freeze. That year I stopped making the smaller bags, and put all the rest in 2 maybe half gallon sized foodsaver bags.
Final cutting of the first lemongrass stalk, showing what was cut off. by
pepperhead212, on Flickr
Some lemongrass in packs of 3, some in packs of 4. by
pepperhead212, on Flickr
Finished stack of Foodsavered lemongrass. by
pepperhead212, on Flickr
For starting this, I buy some at an Asian market, then trim the very end off, then put the stalks in a pyrex cup of water, and root them, in about 3 weeks, changing the water every 3 days. Adding a little clonex helps a little, but plain water works fine. I try to get them with the part of the stalk that gets trimmed away, but that's good, for rooting! Here's a photo of that type of stalk, and some started, and the last, least rooted stalk I had left, after those 4 best ones got planted.
Update - when I start this, I count back 3 weeks from the last frost date, and start the roots. That way, they are ready to plant at the right time.
Trimmed lemongrass stalks, ready to be soaked, for rooting. by
pepperhead212, on Flickr
First roots started on the lemongrass, on 4-21, 8 days after starting. by
pepperhead212, on Flickr
One of my extra lemongrass rootings. by
pepperhead212, on Flickr
When ready, I just stick them about 3 inches into the ground, about 2' apart, and wait!
I forgot to mention - don't bother with the seeds. It's a different species, up to 1/4" at the most, and milder in flavor.