Is there a best time to divide lemon grass? I have a stand that I'd like to divide and put in other areas. Also, should I cut it back when dividing? If so, how much?
What sort of climate are you in? (Please don't talk zones - they don't mean a thing to me! Mention things like temperatures, frosts, sun etc.)
If a warm climate, you can divide lemongrass at any time - how else are you going to get to harvest and use it? It's easier to cut it back before harvesting - just because those leaves can be sharp, and they get in the way of the spade! You can keep the leaves if you want to use them instead of (or as well as) the white bits further down.
If you live in a cold climate, the plant can be divided 'once the danger of frost is over' which I presume means 'in spring'. In a very cold climate, your plant may die right down, in which case, you should dig up the entire plant in early autumn, pot up sections of it and bring them inside and keep at a minimum temperature of 7C. When doing this, just keep the soil barely moist throughout winter, and plant out again in spring.
Digging up the plant is, of course, your opportunity to divide and harvest it.
In my subtropical climate, lemongrass is just too big and unruly for my tiny garden, so I now keep it in a pot. When the pot gets to bulging stage, whatever time of year it is, that's when it gets divided - unless I want to harvest it beforehand. Like any grass, if you cut it, it'll grow back in no time before you cut it again, and it grows.... and the clump gets ever wider and tighter.
I'm in the gulf coast. We typically don't get truly cold weather until late December or early January and it will only last until late February. Full sun (no trees due to hurricanes)
It has outgrown the area that it's in, so I think what I need to do is harvest some and move the rest to a location where it can have more room.
I am in coastal NC so a little colder than you are. Last week I dug up the whole clump and brought it inside the garage to over winter but you could probably leave yours in the ground outside and it would be fine. I would not divide it untill spring time when it starts to show new growth. I would dig up the whole clump and then using a sharp shovel or serrated knife, cut it into as many peices as you need and replant. It is very resiliant and each peice will grow into huge clumps by seasons end.
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