About spring, due to the mass of tissue there for it to root from. If you can get a heat mat, so much the better. I'd lay it on a snaking hillock of soil, so that the concave part is on, but not in, the soil. Roots are very much an environmental factor, so if you can improve one or more of those factors, rooting is more propitious. Mist the crest every few days (or every day, if it's dry in the room - your choice). Is there a chance of a clearer pic of the plant itself? I can't tell what genus it is - maybe you know already, though.