have also put out some florence fennel out this week after nurturing months indoors (I know probably too early) and was careful to avoid disturbing roots. They were in a 4 inch pot for only about a month as they took off fast in greenhouse.
Also have some more seeds come up in greenhouse which will plant on when well established and later try some seeds direct if room. Not sure which variety as got seeds in France and no name supplied on pack.
The other variety of fennel from last year has self seeded everywhere as others noted.