Question for men: Would it be weird to receive flowers from a woman who you have a romantic interest in? Would you be pleasantly shocked and happy to receive flowers on your birthday?
I actually would love it! But not everyone is the same, fortunately. You could try succulents or even an arrangement of them, as they're lovely and don't need much care :)
But since you know him better, reflect on his personality and give it with your best intentions!