Wood sage (Salvia × sylvestris 'Viola Klose')
Salvia × sylvestris 'Viola Klose' (Wood sage) offers intense dark blue blooms from May to June and thrives in full sun.
Complete Plant Information
Overview
Salvia × sylvestris ‘Viola Klose’, commonly known as Wood sage, is a highly valued herbaceous perennial celebrated for its reliable summer structure and intense color display. This hybrid provides dense spikes of dark blue flowers, making it a workhorse in perennial borders from late spring into early summer. Gardeners appreciate the low maintenance requirements of Salvia × sylvestris ‘Viola Klose’, especially its tolerance for dry spells once established.
As a member of the mint family, this Wood sage features upright, clump-forming growth suited for structure in mixed plantings. Its relatively compact size, reaching about 1 to 1.5 feet tall, ensures it doesn’t overwhelm neighboring plants, though it can spread moderately in ideal conditions. It is an excellent choice for attracting pollinators and adding long-lasting vertical interest to sunny garden spaces.
The longevity of the bloom and its adaptability across various soil types, provided drainage is adequate, solidify the reputation of Salvia × sylvestris ‘Viola Klose’. Whether used in drifts or as an accent, this Wood sage brings a cool contrast to warmer-toned summer perennials.
Fast Facts
- Plant Family: Lamiaceae
- Plant Type: Herbaceous perennial
- Hardiness Zones: USDA Zones 4-8
- Size at Maturity:
- Height: 1-1.5 ft
- Spread: 0.75-1 ft
- Bloom Time: May to June
- Bloom Description: Dark blue
- Sun Exposure: Full sun
- Water Needs: Dry to medium
- Maintenance Level: Low
How to Grow
Planting Salvia × sylvestris ‘Viola Klose’ should ideally occur in spring or fall. Ensure the location receives full sun, which is critical for dense flowering and sturdy stems. This Wood sage establishes easily in average soils—it prefers well-drained conditions, performing well even in gravelly or sandy textures, although it appreciates moist, humusy soil if available. Amend heavy clay soils with grit or compost to improve drainage before planting.
Maintenance for this perennial is generally low. While established plants tolerate drought well, providing regular moisture will encourage rebloom throughout the summer. Deadheading—removing the spent flower spikes—is the single best action to promote sporadic, intermittent flowering until the season cools.
Be aware that Salvia × sylvestris ‘Viola Klose’ can occasionally become floppy, especially in very hot, humid climates or if stressed. If the plant loses its upright habit mid-summer, cutting it back sharply to the remaining basal foliage can prompt a tidier, fresh flush of growth. Always cut the entire plant back once the main bloom cycle concludes for a clean transition into winter. Division or softwood cuttings are effective propagation methods.
Gardeners in northern regions (north of USDA Zone 7) will see the best performance due to the plant’s preference for cooler night temperatures. Ensure adequate air circulation to minimize potential fungal issues common to the Salvia genus.
Landscape Uses
Wood sage shines in traditional and informal settings. It serves beautifully as a middle-layer component in perennial borders, lining pathways where its upright habit provides excellent vertical punctuation. Because it is deer and drought tolerant, Salvia × sylvestris ‘Viola Klose’ is a perfect structural element for cottage gardens, where its deep blue contrasts excellently with yellows, whites, and pinks.
Consider planting Salvia × sylvestris ‘Viola Klose’ in substantial drifts for maximum visual impact during its primary May to June bloom period. When planting in masses, utilize its tendency to form clumps, spaced appropriately to allow for slight spread without overcrowding neighboring German Irises or Peonies that finish blooming just as this wood sage hits its stride.
This variety is also highly regarded for its utility off the cutting stem. The dense flower spikes last well in vases, and they dry exceptionally well for everlasting arrangements, adding sculptural dried texture. For a wilder aesthetic, incorporate this perennial texture into butterfly gardens or informal meadow plantings.
Standout Features
Flower Qualities
- Showy
- Good Cut
- Good Dried
Noteworthy Characteristics
Salvia × sylvestris, often commonly called wood sage, is a hybrid perennial salvia that primarily results from crosses between S. Nemorosa and S. Pratensis. Salvia × sylvestris plants, by and large, are branched, upright, clump-forming, perennials featuring opposite, oblong to lanceolate, medium green leaves and showy spikes of tiny, tubular, two-lipped flowers (each to 1/2” long) which range in color from blue to lavender to purple. ‘Viola Klose’ features intense dark blue flowers on stems rising to 15-18” tall. The genus name Salvia comes from the Latin word salveo meaning “to save or heal.”
Tolerances
- Deer
- Drought
- Dry Soil
Potential Problems
This Wood sage variety exhibits some susceptibility to common fungal diseases, notably powdery mildew, leaf spot, and rust, especially in areas with high humidity or poor air circulation. Prevention is key; plant Salvia × sylvestris ‘Viola Klose’ in full sun with ample space between plants. If mildew appears, ensure watering is directed at the base of the plant rather than on the foliage.
Occasional insect pests can include spider mites, lacebugs, whiteflies, and scale. Regularly inspecting the undersides of the foliage can help catch infestations early. Any signs of pest activity often respond well to strong blasts of water or the judicious application of insecticidal soap, particularly against soft-bodied pests like whiteflies.
Frequently Asked Questions
What hardiness zones is Wood sage suitable for?
The Salvia × sylvestris ‘Viola Klose’ is reliably hardy across USDA Zones 4 through 8.
How large does Salvia × sylvestris ‘Viola Klose’ grow?
This herbaceous perennial typically reaches a height between 1 and 1.5 feet and spreads moderately to maintain a spread of 0.75 to 1 foot wide.
When does Wood sage bloom?
This variety produces its primary display of dark blue flowers starting in May and continuing through June, with potential for sporadic rebloom if spent spikes are removed.
What sun exposure does Salvia × sylvestris ‘Viola Klose’ need?
For the best flowering performance and strongest stems, this Wood sage requires full sun exposure in the garden.
Conclusion
Salvia × sylvestris ‘Viola Klose’ offers gardeners a fantastic combination of low maintenance, drought tolerance, and vibrant, long-lasting blue color, making it a cornerstone of summer perennial beds. Integrating this reliable Wood sage into your landscape ensures season-long visual interest and reliable structure where the sun shines brightest. Before planting, confirm your garden falls within USDA Zones 4 to 8 to ensure long-term success with this outstanding perennial.
Companion Planting
When planning landscapes around Salvia × sylvestris ‘Viola Klose’, select partners that thrive in full sun and require similar dry to medium soil conditions. Companions that bloom slightly later help bridge the gap after the main flurry of Wood sage bloom finishes in early summer. Consider pairing it with ornamental grasses like Prairie Dropseed (Sporobolus heterolepis) for textural contrast, or silver-leaved plants like Lamb’s Ears (Stachys byzantina) to enhance the dark blue flower tones.
Excellent partnerships also exist with other sun-lovers that accept lean soil, such as Coneflowers (Echinacea purpurea) or Threadleaf Coreopsis (Coreopsis verticillata). Creating masses of these drought-tolerant species near the Salvia × sylvestris ‘Viola Klose’ will result in a vibrant, resilient border that requires minimal supplemental watering once established.
Propagation Tips
As a desirable hybrid, propagating Salvia × sylvestris ‘Viola Klose’ through division is the simplest route to create exact replicas. Wait until early spring before new growth begins, or fall after the foliage has died back, to dig up the plant. Gently divide the crown into sections, ensuring each new piece has healthy roots and basal buds.
Softwood cuttings are also a reliable method, especially if you wish to propagate several new plants mid-season when the parent plant is actively growing. Take semi-hardened stem tips during the early summer months, remove the lower leaves, and place them in a well-draining propagation mix kept consistently moist but not saturated. Roots usually form within several weeks, allowing you to transplant the new Salvia × sylvestris ‘Viola Klose’ individuals in the fall or the following spring.
