Last year, I planted agastache “Black Adder” in my perennial border, and this summer, it has come into its own. Despite its somewhat sinister name, in my opinion, this plant, also known as “giant hyssop,” is a vast improvement over the much more common “Blue Fortune.” The plant seems to be more robust (this one is well over five feet tall but not floppy) and the flowers are a prettier, less dusty blue.
As for bloom period, this plant has been flowering non-stop since June. The pollinators seem to prefer it to all my other plants – even Eupatorium (Joe Pye weed). The flower buds are nearly black – hence the name, I guess – and the flowers are large, up to eight inches tall. I have cut a few for bouquets and they last well, adding vertical interest to my arrangements.
Black Adder is a carefree plant, and grows happily in zones 6 to 9. It prefers full sun, but will tolerate some shade. One condition it will not tolerate is poorly draining soil.
To make it even more appealing, it has that lovely hyssop scent AND it’s deer tolerant. All in all, it’s a very fine addition to the hyssop family.