I don't know if she picked up fennel smell i guess it could happen. My granny told me a long time ago that she always put a tbsp of sugar in the ground when she put in her tomato plants and she had the best tomatoes ever so I always do this with my tomatoes and I've got to say I do have good tomatoes. Could just be a old wives tale but i do it every time....thought about trying it with my weed but haven't yet. good luck.