Another native plant mostly ignored by gardeners is Scutellaria incana, or downy skullcap. There
are ten or more species of skullcaps in Indiana, with a three or more
being showy garden plants that will stand up with the best of European or
Asian perennials. None are site specific, thus easily grown in the open
garden. Yet, even in gardens that rely heavily upon native plants,
I seldom see any of the scutellaria.
In native habitats the downy skullcap is usually found growing in dry soil at the edge of the wood, or along roadsides. I have seen it blooming well within the woods interior. During July and August we shift into hot and dry with high humidity causing some plants to suffer. Not the downy skullcap. It was made for those conditions and keeps right on performing. Of course, it also responds to a bit of loving care with a touch of decent soil and a modicum of moisture.
My downy skullcap grows along a path at the top of my hillside garden in bright open shade under dogwoods. Garden soil is decent, well drained, and near a limestone cliff edge. I have been growing this species of skullcap for at least eight years. During that time I have not seen insect damage, nor any sign of disease. They bloomed the first year transplanted to the garden, and have bloomed reliably each year thereafter, always putting on a good show no matter the weather. In spite of the good seed set each year, I have not fond them to be weedy. This species is also hardy as an old rock, reaching north into zone 5 and probably zone 4.
The downy skullcap reaches between two and one half and three feet in height. The overall shape is an open vase, but very stiffly upright. I have not seen the stems fall over under the weight of the blooms when hit by wind and rain. The square stems will become quite woody by seasons end. I cut mine back after they have been hit by a hard frost so the stubble will be gone when the new growth begins the following spring.
Individual leaves are four and one half to five inches in length by about two inches in width. The outside edge of the leaf is lined with rounded teeth. Leaves are a deep mat-green.
The numerous blooms are held in racemes at both the top of the stems and in the upper axils. Flowers are of good size, lavender-blue, with each flower having two upper petals fused together to form a hood or cap, thus the common name. Seed pods are shaped like two little saucers stacked one upon the other, with a lip around the edges. As they mature the pods turn tan with violet/purple lips.
For companions you may want to consider any of the summer blooming anemone, Begonia grandis with the red backed leaves, and red lobelia if where you are growing your skullcap is not too dry.
Downy skullcap blooms from July well into August. A time when there is not normally an abundance of color in the shade garden, making it a valuable asset to any shade garden.