If you like your insects then Fennel is most definitely the plant to grow. I have a couple of plants in my small garden and both have reached about 8ft in height this year. Not a problem until you want to photograph what's attracted to them, you end up pointing your camera to the sky, which in my opinion leads to awkward harsh light and a not too pleasing effect. Still I show a couple of real gems that have alighted this summer, a hornet, Vespa crabro, and the wasp/hornet mimic hoverfly Volucella inanis. I also get the whopping beast Volucella zonaria, in my opinion one of the UK's most spectacular flies. Pictures aren't up to much bit a couple of insects on the northern edge of their british distribution ain't too bad.
Hornet - Carlton Nottinghamshire, 01/08/2014
Big Hover', Volucella inanis. Carlton Notts 01/08/2014