Sourced from the Living Architecture Monitor
As the theme of this Living Architecture Monitor issue is biophilia, I decided to cover more plants that can move or sway in the breeze and therefore catch our eye to a greater extent than those that are shorter and more static such as sedum. In this issue I cover the genus Monarda. Two that have been tested and grown on green roofs are Monarda fistulosa (wild bergamot or beebalm) and Monarda punctata (spotted beebalm or horsemint). They are both herbaceous perennials in the Lamiaceae (mint) family characterized by square stems and fragrant foliage. The genus contains the compound thymol, a natural antiseptic that has historically been used as a medicinal plant, especially by native Americans.
Monarda fistulosa (USDA hardiness zones 3 to 9) is more widespread and ranges from coast to coast across most of the US and Canada. Monarda punctata (USDA hardiness zones 3 to 8) has a smaller range and is native to the eastern part of the United States and Canada. They are both somewhat drought tolerant and are often found growing in well drained sandy soils in full sun to part shade. Both form clumps spreading by creeping rhizomes and also tend to self-seed. They are known to naturalize, but M. punctata is considered an endangered species in Ohio and Pennsylvania by the USDA Natural Resources Conservation Service. Both are susceptible to powdery mildew if plants are grown close together without adequate air circulation.
Under favorable growing conditions, plants of M. fistulosa may reach a height of 60 to 90 cm (24 to 36 in) with a similar, but lesser spread. The specific epithet, fistulosa, means hollow like a pipe, in reference to the individual tube like flowers. The dense flower clusters, each about 4 cm (1.5 in) long containing about 20–50 two-lipped, tubular, pink to lavendar flowers, appear at the ends of branches. Below each flower head is a whorl of showy, pinkish bracts. The plants have a long summer flowering period from July into September and attract bees, butterflies, and hummingbirds.