By Dr. Leonard Perry, Extension Professor
University of Vermont
Most gardeners are familiar with the annual sages, or Salvias, usually found in the red versions. There are several perennial sages, however, that come in various colors, some of which are hardy in our cold climate.
Fifteen cultivars of sages were tested over a period of five years at the Chicago Botanic Garden, located in U.S. Department of Agriculture hardiness zone 5. Those that had winter injury there, and so should also in our colder zone 4 (which is most of Vermont), included hians, jurisicii, koyamae, Lubeca, East Friesland, Rose Queen, and transsylvanica. Our trials at the University of Vermont Horticultural Research Center in S. Burlington with East Friesland and Rose Queen confirm that these, at least, are not reliably hardy here in Vermont.
The best perennial sage in the Chicago trials, and one that we've also tested here in Vermont, is the purple-flowered verticillata cultivar Purple Rain. This maintained a tidy habit without cutting back after flowering, as most perennial sages need.
With a flower spike of up to 12-inches in their trials (six to eight inches in ours), it blooms in late June into July, with rebloom in September. Growing 20 to 26 inches high in their trials (15 to 20 inches in ours), it did not produce many seedlings as do some perennial sages. Rich loam soil and plenty of water might give more height in our climate.
A couple of other cultivars that maintain a good habit without cutting back included May Night ('Mainacht') and Vesuvius ('Wesuwe'). Many of the perennial sages were developed in Germany, hence their German scientific names. May Night has deep violet flowers, shorter than Purple Rain, and blooms a little earlier. Vesuvius is similar, but it blooms later, similar to Purple Rain. These two cultivars are hybrids from the species sylvestris that also was hardy in zone 5 and has violet-blue flowers.
Other sylvestris hybrid cultivars that were hardy for them, and have been for us as well, included Blue Hill ('Blauhugel'), Blue Queen ('Blaukonigin'), and Snow Hill ('Schneehugel'). These are much shorter, getting only six to 10 inches high in both Chicago and Vermont. Blue Hill has fairly true-blue flowers, Blue Queen purple-blue flowers, and Snow Hill, white flowers. One problem with Blue Hill that they, and we, have observed is that plants start out compact but fall open prior to bloom, thus making them appear untidy.
Cutting back most perennial sages right after first bloom (except Purple Rain, which remains tidy) keeps them compact through the season. Some references say this makes them rebloom in early fall, but in the Chicago trials plants rebloomed well whether they were cut back or not.
Given sun, adequate water in a well-drained soil, and moderate fertility
in a soil with pH of 6 to 7 or so, perennial sages are a good choice for
perennial gardens. With nice upright spikes of early summer bloom (usually
blue to purple), they rebloom in fall in most years. They are usually free
of pests although occasionally are bothered by Japanese beetles or powdery
mildew. Try combining them in containers or fronts of borders with ornamental
grasses, yarrows, daisies, daylilies, coreopsis, or the silver foliage