I've always liked the fast-growing, non-stop, blue-blooming, sun-loving, drought-enduring 'Indigo Spires' salvia. One weakness it does have is that grows so fast, and never stops blooming that it gets so big it tends to flop and fall over, especially in well-tended (read fertilized and watered) gardens. You can, and should cut it back occasionally, but most gardeners have a hard time bringing themselves to cut off the deep blue flowers spikes that just get longer and longer.
Enter 'Mystic Spires Blue' salvia, a relatively new introduction that is getting acclaim from professional and amature gardeners alike. In almost all respects 
'Mystic Spires' is identical to 'Indigo Spires' except that it is much more compact, getting maybe 3 to 4 feet all instead of flopping over at 5 to 6 feet tall like Indigo. It still benefits from a shearing, maybe only once or perhaps twice, to keep it bushy and floriferous. I like to cut back a portion of the growth in early summer, leaving about half to cut back later after the first cut flushes and blooms. It is also non-stop, and instead of being relegated to the back of the flower bed due to size, it can be brought forward where it will be appreciated by not only us, but the flocks of butterflies and other pollinators visiting its dark blue flowers. Does best in full sun, average soil, water and fertility.
It can be seen in the IDEA Garden in the North Texas Winners section by the patio and also in the uppder garden near the Two-wing Silverbell (Halesia) tree.
