“Blue Sage” is a common name referring to several species within the Salvia genus, primarily Salvia farinacea (Mealycup Sage) and Salvia azurea (Azure Blue Sage). Both species are known for their vibrant blue coloration and upright growth habit. This guide focuses on the distinguishing physical characteristics of these plants.
Physical Structure and Growth Habit
Blue Sage species are generally upright, herbaceous perennials or subshrubs, meaning their stems are not entirely woody. Salvia farinacea typically grows into a mound or rounded clump, reaching 18 inches to 3 feet tall. The stems are often squared, slender, and erect, sometimes developing a purplish tint or a powdery, mealy texture near the top.
Salvia azurea is known for a more airy, slender, and often taller growth habit, sometimes reaching up to 4 feet. Both species are clump-forming, with new growth emerging from a central base. Their overall architecture provides a vertical accent, as the flower stalks rise well above the main body of the foliage.
The stems of Salvia farinacea are covered in fine, white, felted hairs, which creates the “mealiness” that gives the plant its common name. This feature is particularly noticeable on the upper stems and flower structures. The plant’s strong, upright structure makes it a popular choice for adding vertical interest to gardens.
Characteristics of the Foliage
The foliage provides a contrasting base for the vivid flowers, often featuring a muted color that enhances the blue tones. Salvia farinacea leaves are typically lance-shaped and narrow, growing in opposite pairs along the square stems. They are usually medium green, sometimes exhibiting a hint of gray, particularly on the undersides.
These leaves are aromatic when crushed and may have margins that are entire (smooth) or slightly serrated. A distinguishing trait of Salvia farinacea is its nearly glossy or smooth texture, setting it apart from many other sages that are densely hairy. Leaf size is modest, generally reaching up to about 3 inches in length.
In contrast, Salvia azurea leaves are usually narrower and more linear, often described as gray-green, which complements its true sky-blue flowers. The foliage of S. azurea is less dense than S. farinacea, contributing to the plant’s more open and graceful appearance. Both species maintain their foliage throughout the bloom period.
The Signature Blue Flowers
The defining feature of Blue Sage is its vibrant blue flowers, which are borne on tall, striking spikes. The inflorescence of Salvia farinacea is a dense, upright spike (raceme) that can be 4 to 8 inches long. The flowers are packed in tight whorls along the upper portion of the stem.
The corolla color ranges from dark blue and violet-blue to purple, with white cultivars also available. A key visual element is the calyx, the small cup holding the flower, which is often deeply colored blue or purple and covered in fine, powdery white hairs that define the “mealy” appearance. This dense, colored calyx gives the entire flower spike a rich, saturated look, even before the small, tubular flowers open fully.
Salvia azurea is celebrated for its pure, true sky-blue color, which is relatively rare among garden plants. Its flowers are borne in more spaced, loose whorls along the tall, slender spikes, creating a more airy and delicate visual profile than S. farinacea. The individual flowers are tubular and two-lipped, reaching about one inch in length.
This species blooms later in the season, often from midsummer until the first frost. The color saturation and the open arrangement of the flowers on the spike contribute to the plant’s common name of Azure Blue Sage.