My experience with Salvia leucantha in my zone 7a garden is that it sometimes survives our winters and sometimes doesn't. It really depends on the type of winter we have. I had one for three years and then one spring we had an extremely warm spell followed by an extremely cold spell around Easter and the plant did not return. Another thing that some say dooms this plant is cutting it back in the late fall/early winter and water getting down its stems and it rotting. Not really sure if that is the case since the one that survived several winters here was typically hit with ice and had stems crack off and open stems sitting exposed all three winters and it survived until the last year when we had the weird spring weather.

Another tidbit I failed to mention about Mexican sage in the northern reaches of its winter hardiness is to plant in early in teh growing season so that it can have as much time to establish itself beyond that container rootball before its first winter. This is particularly true with heavy clay soil since container peat media and mixtures thereof do not readily "mesh" with the compact, fine particles of clay in the planting hole as nicely as a loam or amended sand.

These are reportedly winter-hardy only to zone 8. So would be considered an annual in the mid-Atlantic region. Come to think of it, I got mine at a nursery known for stocking unusual plants, both native and exotic. Alexandria looks like it's in 7b and perhaps that is a somewhat protected location. 20 years is too long a time to say they've just been lucky! I've been growing this plant for a few years now in a pot so I can overwinter it in my small greenhouse. I cut it back severely, place in a cool shady place and water sparingly until late winter, when I bring it out into more light and resume watering/feeding. Always have a nice shrub for summer and blooms for autumn. You're right, the bees and butterflies love it, and the blooms are wonderful this time of year. (But don't forget Japanese anemone, toad lily, Sheffield daisy, Montauk daisy and many roses. Hydrangea blooms are lovely in their antique shades from chartreuse through pinks, mauves to deep purple and burgundy. Some of the berried plants [winterberry holly, wintergreen, roses with prominent hips] are showing good color, too.) It's still at peak bloom here, with a low of 35 expected tonight :-( I should take a division in spring and try overwintering that outside next winter.

I planted a couple of Allen Chickering sages next to a parking lot, in front of a hedge of ligustrum, in a semi-watered location in Fountain valley, Ca (Coastal Orange County). By semi-watered, I mean a place where extra water from the sprinklers behind the ligustrum runs out onto the surface, but doesn't result in a thorough watering. I think the soil is slightly moist most of the summer, and moist all winter. The Allen Chickering have grown quite slowly compared to Pozo Blue and Whirley Blue, two other S. clevelandii hybrids (or cultivars?). Allen Chickering is evergreen, and mine have made attractive, if slow growing shrubs that bloomed last summer. Everything about Allen Chickering is a little smaller and slower than Pozo Blue, but that might make it easier to manage in the long run. The flowers are deeper blue and smaller than the other S. clevelandiis.