What are your growing conditions? Exposure, full-sun, partial? How deep are your window boxes?

Jane

Sage, Lavender....

Josh

Mint is pretty fragrant, and easy! Sometimes too easy...

Assuming the OP has good sun, I like scented geraniums, lemon thyme, lemon verbena, mini roses (although they do get quite big with large root systems, sweet pea (cool), nicotiana.

Bees are attracted to flowering herbs and flowers and should be considered if your windows are left open.

Jane

If it is aroma you want, you can't beat Basil. It will also stimulate the appetite. Most showy flowers do not have a strong enough fragrance to travel on the moving air. Al

Petunias are extremely fragrant, although may be boring to some people. I often get wafts of their spicy fragrance inside our apartment from one hanging basket several feet away from the building.
I recently sent for some Mignonette seeds as they are supposed to be very fragrant, but their flowers are not showy. I thought I would tuck them in with other more showy flowers.

Here is a link that might be useful: mignonette

I am with Jane on the scented geraniums! I have one that smells the whole room up while everything less is out of bloom.
This one plant made the whole nursery house smell good and I had to ask them what it was. This is the plant and not a disappointment at all! Love it, especially when the sun hits it.

It almost smell like citrus and something else I can not put a finger on.
Now, many around here want one.

Mike

{{gwi:2666}}