Green Roofs - Living Architecture Monitor Fall 2020 - 12

hot pink to describe the five to eight petals that make up the
flower. The flowers are held on stems that arise above the basal
clumps of succulent, blueish green, needle-like leaves that may
be up to 5 cm (2 in) long. When grown with sedum, the flowers
stand upright above the prostrate sedums, thus providing a
vertical interest. These long blooming showy flowers make it
an excellent accent plant, but they also work very well when
planted in a mass. To quote Ed Snodgrass, "A gentle breeze will
set the flowers dancing like hovering butterflies". Speaking of
butterflies, the flowers attract numerous butterflies and bees
that serve as pollinators.
Besides its visual attributes, the species is great choice for
green roofs due to its high drought tolerance. In its native
environment P. calycinus is often found in dry environments
under full sun growing in rocky or sandy soils that are well
drained. This is the environments that also describes typical
green roof substrates and growing conditions. Supplemental
irrigation is not necessary, but they will perform best with up
to 2.5 cm (1 in) of rain per month. Too much water will kill the
plants which is why good drainage is essential. Also, they are
not subject to any serious insect or disease problems.
As mentioned above, P. calycinus is classified as a USDA
Zone 6-9 plant and is unlikely to survive a normal Michigan
winter. However, it is a prolific seeder and can be treated as
a self-sowing annual in such locations as long as bare soil
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present to give the seed a chance to germinate without being

LIVING ARCHITECTURE MONITOR / FALL 2020 / 10

shaded out. When there is
no open substrate it will
tend to eventually disappear.
This was found to be true in
a published replicated study
performed on the Communication Arts Building on
campus where it died off after
five years (Getter et al. 2009.
Solar radiation intensity influences extensive green roof
plant communities. Urban
Forestry and Urban Greening
8: 269-281) and in an unofficial study on my doghouse
where it disappeared after
two seasons. Whether you
call it Phemeranthus calycinus or Talinum calycinum,
it is a great plant for cold
climates despite the lack of
cold tolerance and even a better plant in warmer climates,
especially within its native
range. I highly encourage its
use on green roofs.

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
co-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.sible. The
green roof provides ancillary
outdoor classroom space that does
not conflict with the playground
area schedules and is utilized
in various school subjects and
activities: literacy, math, science,
STEM, art, movement, and
even counseling. Most importantly, the green roof offers a
positive emotional experience for
students, who have relayed the
following observations: 

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