I was inspired to write this when I noticed that Bob mentioned flower shops in two separate episodes.
When Bob ordered the hypnotized Bart to tell his family he had been at the flower shop, this was not simply a weak excuse he came up with at the top of his head. To him, it was a perfectly logical place for a boy to go.
From a young age, Bob had a fascination with flowers. When he was around four, maybe five, Bob noticed that his mother constantly came home with various kinds of bouquets, both huge and small. When Bob asked Judith why she always had these flowers, she told him, "It's because people love and admire your Mummy."
Bob's father, and sometimes Cecil, would complain that the smell of the flowers became a little overpowering at times. Bob never minded. He liked how many different kinds of flowers there were: lilies, big daisies, roses, sunflowers, daffodils, tulips, forget-me-nots, and so many others. Except lilacs, because Judith was allergic to them.
Bob especially liked to admire the colours of the flowers. Whenever he bought a bouquet for his mother, he made sure the flowers were not just one colour. Sometimes, little Bob would help out at the flower shop and get to make his own bouquets, albeit small ones. The florist always used a rose and baby's breath for the mini-bouquets, and was quite fussy about how to cut the flowers and how to curl and tie the ribbons. Bob didn't mind. He respected people with high standards, as such people seemed to be a dying breed.
Of course, Bob had to be careful around flowers at times. Cecil, and later Krusty, were both partial to the tired squirting flower prank. Bob usually saw through it, but they would squirt him anyway.
When Bob married Selma, she had wanted mostly pink and white flowers for the decorations and bouquets. The lack of variety was a disappointment for Bob, but Selma was not terribly imaginative or passionate about flowers, especially since she couldn't smell them.
Flowers became something of a happy place for Bob if he ever found himself sedated or in solitary confinement. Of course, sometimes thinking about flowers (especially the primary-coloured ones) would mutate Bob's innocent thoughts into visions of Bart Simpson taunting him.
Prison was such a grim, colourless place, and most of the other inmates had little appreciation for beauty. If a flower did poke its way through the prison yard, it often got stepped on. That was why Bob wanted to open his own flower shop when he got out of prison, to contribute to more colour and beauty.