The anise-scented hyssop is a sturdy perennial much neglected by plant books and gardeners. I'm not sure why. It's a pretty plant with green, slightly purple-tinged foliage that smells pleasantly of anise, and makes great tea with other tea herbs. This one can grow to 4 feet or more, in good conditions. It sends up spikes of flowers that remain in bloom from midsummer through September. Bees love it, and are purported to make good honey from its pollen.
Although the anise hyssop is not susceptible to garden pests, it does tend to wilt in very hot sunshine. But when adequately watered, the hyssop is one of the nicer perennials in the garden.
The only hazard to this plant, if you can call it that, is that it's a prolific seeder, due to the hundreds of tiny flower heads it creates. So you might end up weeding unwanted hyssop throughout the season. This shouldn't be too much of a problem as they're not invasive, and are easy to recognize coming up.