Salvia azurea grandiflora is found as a native in the Great Plains and is zone 5 hardy. It has evolved to grow through prairie grasses and is tall and thin. It will form a clump that can occasionally be divided. It can get from 2.5 to 4 feet tall and about 1.5 feet wide. It does well in loam and sandy soils.
There are several forms, including Nekan, found inear the Kansas-Nebraska border.
I do water as needed which is pretty often in TX in the summer. I planted it in a bed with good soil, full sun that will get supplemental water so lets see how tall it gets...I will take pics when it starts to put out some growth. It hasn't wilted so its doing ok thus far.
Salvia azurea grandiflora is indeed hardy to USDA Zone 5. So is the form Nekan, which gets its name from the states of Nebraska and Kansas. It was found near the state lines of those two states close to Colorado.
I had 3 that grew quite tall and only had a few flowers, not very impressive. I am hoping its because its their first year and we have had such a heat wave here. Not a good year to judge a new plant.