Last February, we had a very unusual hard freeze. It killed a lot of plants.
The prior year, I had gotten an agave from a local nursery. It was a nice specimen, about 12 inches wide; it cost $25. In the freeze, it died. So I removed all the dead matter above ground. In the springtime, I watered it sparingly. After a couple of months, there was no visible growth.
One weekend, I went and bought a plant to replace it. The new plant is a Dasylirion wheeleri, aka sotol, or desert spoon. These things grow in the mountains, where it actually snows sometimes. Ought to be able to tolerate a freeze or two.
When I dug a hole for the sotol, I found a lot of thick, moist, viable-looking root from the agave. Somewhere, sometime, I had read about propagation from root cuttings. So I used some cactus potting mix, in a 12-inch terra cotta pot. I put the root cuttings in a coil, about an inch below the surface. I placed them outdoors, in dappled shade. Then, I waited. I watered them sparingly, occasionally.
Last week, I noticed that two of the four have sprouted new plants.
At this point, I only have to wait about ten years, and I will have two decent specimens.