Written by Emily Nagoski, Ph.D.
It's what giving flowers is really about. What flowers you bring almost doesn't matter, what matters is that it occurred to you to do something for her (a) without her asking and (b) when she wasn't right there in front of you. Both of these conditions are important.
(a) Without her asking. You know her well enough to predict what might make her happy. You listened and remembered when she mentioned something she likes. You know what sort of thing might give her pleasure, and furthermore her pleasure is important enough to you to go a little bit out of your way. We like that.
(b) She wasn't right there. She's part of your internal experience; you carry her in your heart all the time. Showing her that this is true is a good thing to do.
CAVEAT: There is a circumstance where the specific flowers can earn you bonus points. If she has mentioned in the past that a particular flower is her favorite, you should get her that. (I think it is okay to say, "I remember you said they were your favorite" if she doesn't spontaneously mention it.)
It doesn't have to be flowers, of course, you don't even have to bring anything at all. You could just say, "I was at place X and saw thing Y and it made me think of you." Technology can be helpful here too. Have a camera on your phone? Take a picture of thing Y to show her or email her. Or if she's got something important happening in the morning, give her a call in the afternoon to ask how it went.
So what I'm saying is: provide evidence that you thought about her when she wasn't there. Chicks dig it.