In most species of plants, blue leaves are uncommon. There is a tremendous variety of blue hostas which can have spectacular foliage. There are many options with blue hostas with sizes from mini to giant, smooth to seersuckered leaves, leaves cupped up or down, and forms from mound-shaped to vase-like. Blue hostas are an easy way to add drama to almost any garden.
The genetics from the original species hostas that have a blue or gray color are from H. sieboldiana, H. kikutii, H. pychnophylla, H.nigrescens and H. hypoleuca.
What Makes Some Hostas Blue?
The wax that gives hostas blue or gray color is explained by famous hosta expert W. G. Schmid:
The shiny layer on hosta leaves is based in the cuticle, which is the topmost layer of the leaf epidermis. The epidermis is the outer multi-layered group of cells covering the leaf. It forms the boundary separating the plant’s inner cells from the environment. The epidermis serves several functions: protection against water loss, regulation of gas exchange, and secretion of metabolic compounds. The epidermis is usually transparent, since epidermal cells lack chloroplasts and outermost coat is a waxy cuticle that prevents water loss. Thus, the plant cuticle has a primary role in water conservation, but is also an important barrier against the entry of pathogenic microorganisms. The cuticle consists of a cross-linked polymer called “cutin” and provides a protective wax layer that seals the plant surface. The waxy layer of the cuticle is obvious, appearing either as a shiny film on some hosta leaves or as a glaucous outer covering that gives a gray or blue appearance to hosta leaves. That glaucous type of cuticle has light scattering crystals present in the wax, which give a dull, rather than a shiny appearance. Several factors can determine how shiny the leaf surface appears including the amount of wax, the type of wax, the crystalline structure of the epicuticular wax, leaf texture and in some genera leaf hairiness. The cuticle can be damaged by external forces like rubbing or mechanically polishing through which it becomes shinier because the structure of the epicuticular wax is physically changed.
Blue Hostas and Maturity
It often takes from four to five years before a hosta is considered “mature.” The maximum output of wax, and thus the bluest blue or grayest gray, is generated at maturity. Note that hostas can emit the blue-coloring wax at different times in the season, making some bluest earlier in the season and some bluest later in the season.
Where to Plant Blue Hostas
Be careful where you plant your blue hostas because too much sun can melt off the wax. At the same time, no hosta will thrive in deep shade with no sunlight. Besides too much sun, the wax can also come off from rainfall, overhead watering or wind, but sun and heat will cause the most damage. Without the wax, the hosta can be exposed to burning.
In the southern USA hostas may remain blue only until late June whereas in the north they may remain blue the entire season in less heat. Since most blue hostas only have one flush of leaves per year, if blue color is lost at any point during the season, it will remain so until the following year. For best results, plant where they will receive some morning or evening sun and avoid the hot overhead afternoon sun.
Gray and Blue Hostas in Landscape Design
- Blue hostas make a nice background in the garden.
- Remember to place blue hostas in shady (but not total shade), or morning sun areas in the yard for best blue coloration.
- When planting blue hostas side by side, you can add variation with contrasting leaf sizes, textures, or shapes.
- Large areas of blue hostas give gardens a peaceful feeling.
Like other plants, a blue hosta will take on a different look depending on its surroundings. Notice the difference in the three different landscapes pictured below. In landscape design blue hostas can be used in a mass to create a soothing aura. To create a dazzling effect, use blue hostas with green or orange plants or other hostas . For maximum impact, plant blue hostas beside yellow hostas.
Blue hostas in various landscapes