Once the plant is turning brown, I can start harvesting....if I'm impatient. Which I am! I'm out of turmeric and am eager for a resupply. But usually I can let the plant die back even more, as long as the weather isn't daily rain. Below, this plant isn't quite ready for harvesting, but what the heck. It's actually a plant I missed harvesting last year, so it matured ahead of the other plants around it.
In fact, I missed harvesting a number of plants last year and the tops died completely back and disappeared. Last winter I accidentally found a number of them and was able to harvest the roots. The hidden turmeric roots were perfectly fine. So I discovered that once the plants die back, the roots can be harvested for use at anytime up until they resprout.
I'm finding that the larger the piece that I plant, the larger the fan of roots that I can harvest. Of course that assumes fertile soil and adequate water. Example, this plant I just dug up.........
Wow, what a large clump!!!! As I said, it was a plant I missed harvesting last year. Pretty impressive how much I can get from a missed plant.
Once I harvest the roots, I cure them by putting them in a dry, airy, shaded spot. Then I store some in the frig wrapped in a damp cloth (so that it's handy) for fresh use. Some sliced up and in the freezer for cooking (it gets soft but it's fine for cooking). Some I will dehydrate then powder (I use a coffee grinder). But the bulk gets stored in the ground where it will stay in good condition until I use it or it starts to sprout.