You have to grow them from seed or divide them with roots/bulb intact in the fall.

BUT: they should not be planted near some/many plants because fennel is alleopathic will harm them or can even kill them.

BIGGER BUT: Fennel attracts ladybugs, syrphid flies, tachinid flies, parasitoid wasps and hoverflies.

I found this out the hard way last year. For the first time ever, I had two BST chrysalises that ichneumon wasps came out of. :( I'm not taking the chance this year and will be giving my fennel away. That might be a little extreme because I've had fennel in other gardens and never a wasp, but I am not ready to see a nasty wasp in my butterfly cage ever again!

http://www.seedaholic.com/foeniculum-vulgare-purpureum-bronze-fennel.html

(the link calls the pests 'beneficial' ... not to me!!)

Thanks.

I don't know this, clearly, but I guess that wasps are attracted to fennel because of the caterpillars. The wasps that we don't want are insect eaters, not vegetarians. The same thing is true of lady bugs, they eat very small insects not the vegetation. I would imagine the same would be true of most of the other insects mentioned as "beneficial." The context here is that some insects are beneficial to the fennel because they feed on caterpillars, which will eat much of the fennel if not "controlled."

So, fennel attracts these insects because it is so good at attracting black swallowtails.

Eastern Black swallowtails are the only butterflies that I try to help grow by putting their caterpillars in cages. The wasps and birds that discover one will come back and keep eating the caterpillars.

I also try to put the fennel in different parts of the yard, sometimes in places that are fairly well hidden, so the cats will have a better chance to survive.

I see what you mean, but it was very distressing finding that wasp in my cage! Maybe I've never had them before because my main host plant is rue, and the eggs and cats are harder to see. (if that's how the wasps find them.) Or maybe I've never had them because I'm obsessive about 'egg hunting' and bring every one of them inside! :)

I've noticed that the big weedy fennel plants growing on the corner lot where they are now putting up a building was the nursery for the big yellow butterflies we see here once in a while. Swallowtails are the biggest most colorful bugs we have around here in urban San Francisco. Wasps and a lot of things must be attracted to these weeds but that they are where our swallowtails come from is more than enough reason to want to grow them. The more butterflies the better.