Green Roofs - Living Architecture Monitor - Summer 2018 - 7

Photos courtesy B. Rowe

MONARDA FISTULOSA OR
BEEPALM GROWING ON AN
EXTENSIVE GREEN ROOF.

"MONARDA PUNCTATA ALSO ATTRACTS BUTTERFLIES
AND OTHER POLLINATORS, ESPECIALLY WASPS."

grubs, pest caterpillars, and
other harmful insects.
Both M. fistulosa and M.
punctata were trialed at the
Chicago Botanic Garden
(Hawke, 2015, Chicago Botanic Garden Plant Evaluation
Notes, Issue 38). Monarda fistulosa was tested at a substrate
depth of 15 cm (6 in) and given
an overall good performance
rating of 4 stars (out of 5).
Monarda punctata was grown
at depths of 10, 15, and 20 cm
(4, 6, and 8 in) and was given
a fair 3 star rating across all
depths. Plants were watered
regularly during the first year
to ensure establishment and
then during extreme drought
periods in subsequent years.
In trial at Michigan State
LIVINGARCHITECTUREMONITOR.COM

- BRAD ROWE

University (MSU), M. punctata
was one of the species used to
evaluate recycled substrates such
as foamed glass and crushed
porcelain against a standard
heat expanded shale (Matlock
and Rowe, 2016, Ecological
Engineering 94:244-254). Plugs
were planted in May 2013 in a
substrate depth of 10 cm (4 in)
and M. punctata was found to
be one of the best performers,
regardless of substrate type. Irrigation was supplied during year
1, but thereafter the plants had
to rely on natural rainfall. Even
after five years, some plants of
M. punctata are still appearing
every year as it has either reseeded itself or resurrected itself
from surviving rhizomes.
In contrast, in 2011, M.

fistulosa was planted along with 16 other herbaceous perennials and
grasses at depths of 10 and 20 cm (4 and 8 in) on the roof of the
Molecular Plant Sciences Building at MSU (Vandegrift, 2018, MS
Thesis). Although coverage was decreasing over time, the species
was still present until 2016 when there was a major die-off of most
of the herbaceous species. No irrigation was supplied after year 2.
Their disappearance was likely due to a drought during that spring
and summer of 2016. During a 57 day period from May to July, the
total rainfall was 3.28 cm (1.29 in), which was roughly a third of the
normal rainfall for that time of year.
Although both of the Monarda species have great potential for
green roofs, evidence suggests that like most herbaceous perennials,
irrigation may be required during drought periods to ensure longterm survival. This is especially true for M. fistulosa because of its
greater biomass.
Brad Rowe has been conducting green roof research at MSU since
2000. Research topics include plant selection, growing substrates, carbon
sequestration, stormwater runoff, energy conservation, and roof vegetable
production. He was the founding chair of the GRHC Research Committee
and received the GRHC Research Award of Excellence in 2008. Brad also
teaches a course on green roofs and walls at MSU.
LIVING ARCHITECTURE MONITOR / SUMMER 2018 / 7

http://www.LIVINGARCHITECTUREMONITOR.COM

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