Rhys, all being well you sowed an early variety such as Jolant, Bulgarian Giant or King Richard, all of which bulk up in summer. Compared to Musselburgh which bulks the following spring.
I would say about mid March undercover for them. Or now if they have warmth to keep the chill off, so they are not tricked by any cold into thinking they have been through winter and need to flower, usually from July if it happens.
