Giving a man a birthday floral arrangement will not emasculate him. Believe it or not, men like receiving flowers too. In fact, surveys have proven that the majority of men would be happy to receive flowers on any occasion. So, whether it be a brother, boyfriend, or father, there's a good chance he'll appreciate a flower arrangement.
The perfect choice of floral gift to give a male would be one of a vivid color (no pinks or pastels). Think orange or yellow unless, of course, you're sending birthday flowers to your lover. In which case, red roses are an excellent and appropriate way to say “I love you.”