It's a lovely gesture, but it does mean that the host has to stop what she is doing, fetch a vase, arrange the flowers in water, and find a spot where your lavender lilacs fit in with her burgundy hydrangeas. If you'd like to bring flowers, present them in a vase. It makes less work. For you only. A host shouldn't feel obligated to put out any gift.
Chances are, the host has carefully picked the night's wines.
Here are other hints to keep you on your host's good side. Don't bring an uninvited guest. Hosts plan for a specific number of people. Respond on time. It is never assumed that you are not attending a party just because you haven't RSVP'd.