Hi Sara,
I suppose, the best best time(s) for taking Drosera cuttings
is when the plant is in active growth. So far, I've been unable
to root cuttings from any annual Drosera but most other species
can be propagated asexaully in some manner, either by using roots
or leaves usually. Some plants, like D.adelae grow all year and
can be propagated all year round.
Dave Evans