fennel inhibits other plants apparently so that'll make your decision easier, peggy sue! if you DO plant it it'll have to be away from other plants. Will dig out my plans tonight and post again.
I got Louise Riotte's book on companion planting - "Carrots love Tomatoes and Roses love Garlic" a couple of years ago. I tried to make a chart of what you could grow together. It was impossible as the information kept contradicting itself. In one chapter it would say plant A with B and then the next say you can't plant A with B!
It would also seem to me that any planting would have to be very carefully timed to make sure the plants were together at the right time - not easy as each plant grows at different rates - some are annual, some biennial, etc. This was not covered in the book.
And its very hard to prove that something is preventing a disease/insect attack if the disease/insect does not show. I would guess that if some rigorous scientific experiments were conducted the results would be very marginal at best.
I suspect companion planting is more a case of wishful thinking than hard fact. The best companion is the gardener giving TLC to the plants.