Aurora Bloom
A glowing crystal that grows out of open ground while an aurora is overhead, and is gone by morning.
The one reason to be outside after dark. Most nights you're indoors or asleep, so the night worth going out for announces itself from a long way off: a field of blooms lights up a hillside. Cut them while they're up. By dawn there's nothing there.
Auroras are most common on cold worlds. See Weather.