Green Roofs - Living Architecture Monitor - Summer 2018 - 6

PLANT PROFILE

TWO BIOPHILIC PLANT SPECIES
THAT SWAY IN THE WIND
BY BRADLEY ROWE, MICHIGAN STATE UNIVERSITY, EAST LANSING

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.

n 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,
LIVING ARCHITECTURE MONITOR / SUMMER 2018 / 6

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 twolipped, 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.
Monarda punctata is generally shorter, but can grow to
45 to 60 cm (18 to 24 in) tall
with a spread of 23 to 30 cm (9
to 12 in). The specific epithet,
punctata, means spotted, again

in reference to the flowers.
Here the two-lipped yellow
flowers are dotted with purple
spots. In contrast to M. fistulosa, flower clusters do not rest
at the end of the branches, but
are arranged along the stems,
each subtended by the showy,
pink to white bracts. The
bracts are actually the more
ornamental feature as they are
more conspicuous and last for
a longer period of time. Flowering occurs during June and
July. Monarda punctata also
attracts butterflies and other
pollinators, especially wasps.
Although at first thought we
may think of wasps as being
negative, the flowers attract
predatory wasps that are very
beneficial as they help control
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