Sonoma County Master Gardeners Helping Sonoma Gardeners

I was wandering around the insectory--the garden that attracts beneficial insects which help deal with grapevine pests--at Benziger Winery in the Sonoma Valley last fall--gazing at the stunning displays. In addition to well-fulfilling its pest control function, this garden is dramatic and beautiful. One of the most gorgeous combinations was bright yellow Kniphofia, lacy pink Gaura and feathery Pennisetum interspersed with drifts of purple-blue Perovskia, commonly known as Russian sage.

I've long admired this perennial, but hesitated to plant it because I was afraid that it was not deer resistant--and we are completely un-fenced on Sonoma Mountain. Then recently, Sara Malone and I were touring Rosemary McCreary's smashing gardens on the other flank of Sonoma Mountain, and there were swaths of it in her unfenced section. "I thought the deer would mow that to the ground" I exclaimed. She responded, "Well, they've never touched this".  And, like other fragrant, wooly-leaved plants such as Lavender and Santolina, Perovskia is indeed on most deer-resistant lists.  

Perovskia is neither Russian nor sage; rather it is native to southwestern and central Asia--Afghanistan to Tibet. It is a member of the Lamiaceae (mint) family, as is genus Salvia (sages). It was probably first called sage because its foliage smells sage-like when crushed.   In cultivation since the mid-1800's, it is botanically a subshrub, which means that it has both woody tissue and soft herbaceous tissue. Perovskia was named the 1995 Perennial Plant of the Year by the Perennial Plant Association.

The foliage of Russian sage is gray-green, with small, finely dissected tooth-edged leaves and silver white stems.  The foliage is pungently scented, which is pleasingly apparent when crushed or brushed against. The tall, long-blooming lavender-blue flower spikes lend a cool, airy cloud of color to the garden mid to late summer. Even in winter, groups of the white stems make an attractive and striking feature. Its loose, open habit makes this perennial an effective filler in the back of a border. Wide sweeps of it will attract hordes of bees, too (one of the reasons it was in the insectory).

Perovskia's silvery foliage and open architecture are emblematic of the Mediterranean idiom. Use it as an individual plant or two in small areas, ranked in a row as a wide hedge, or in broad swaths to magnify its presence. It combines well with ornamental grasses and white or yellow-flowered perennials, and something strikingly red or orange (such as the Kniphofia at Benziger). Other possible combinations could include red-leafed Berberis, Ceanothus for complementary blues and contrasting dark foliage, or blending with other silver-foliaged plants such as Achillea.  Miscanthus, Nepeta, bronze fennel, and Echinacea purpurea would also make good companions.

 
The most commonly planted variety is Perovskia atriplicifolia--it's a bit of a rampant-spreader and grows to about 3-4 feet. [There is some confusion in the nursery trade, and plants sold as this species are thought by some to be a hybrid between P. atriplicifolia and P. abrotanoides.]
    
Cultivars include 'Longin', which is a bit better-behaved, with a more upright, formal growth habit to about 3-4 ft. tall and wide; 'Blue spires' which has larger flower-heads and grows to about 4 feet, flowering from mid-summer into fall; 'Little Spire', which is a bit more compact, growing only to about 2 feet tall; and 'Filigran' which is the sturdiest and most upright of any Perovskia, and features fine, lacy (or filigreed, as the cultivar name suggests) leaves.

Perovskia wants full sun and little water--it is quite drought tolerant.  Monitor soil moisture, taking care not to over water. It prefers relatively poor, well-drained soil, so fertilizing is unnecessary. Fertile soil will boost 'leggy' growth and will require support to prevent the plant becoming untidy. Good drainage and aeration will enable the plant to survive through our wet winters, as the plants will rot if the soil is too moist. With too much shade or too rich a soil, it may need staking, but in full sun is quite woody & stands upright without assistance.

Container-grown plants are best planted in early spring, but they can be planted out through the summer and into fall. Water regularly during the first growing season to establish a deep, extensive root system.

Cut Perovskia back hard - the entire plant to basal shoots of about 6 inches - before new growth emerges in spring, to encourage a denser habit.  If it is not pruned hard enough the growth can become lax and droopy, particularly when the plants are young.

Hardy to the lowest temperatures we see in Sonoma County, Perovskia also seems to be fairly resistant to leaf pests and most diseases. And now that I know that deer will leave it alone, I’m going to give Perovskia another try!