I can only tell you that the heater in the propagator raises temp by a few degrees. i only checked temp with my hand and its empty at the moment. apart than a few of strands of hc, i haven't cleaned out yet growing very very slowly, which im pretty tempted to leave till spring just to see if it survives all year with just natural sunlightAndy; what temp is the water at inside the propagator, can you measure it?
FYI, HC will grow well out side in a pot just like a typical plant.
The only issue is if it gets below freezing, then you need to take it back inside.
Water it daily if the temps are above 15C. Partial sun works well.
I grow it here in CA, USA where the humidity is often well under 20% during the day all summer long.
Ive got a double size propagator thats thermostatically controlled at a stable 20C and a 45w 6500k growlight suspended above the propagator, so hopefully that should help things along.
Does that sound ok?