Microclimates in the Landscape
Texas A&M AgriLife Extension Service — Galveston County Office
January 25, 2017
PHOTO CREDIT: William M. Johnson
The cold snap in early January produced a quite rare spectacle known as frost flowers. Frost flowers aren't real flowers at all. They are natural ice sculpture formations that sometime take on the form of flowers.
The date was Friday, January 6, 2017. Nighttime temperatures in my home
landscape dropped to 27
degrees for a few hours. On
that night, I set out a single
16 oz. capacity Solo cup
which I had filled to the
brim with tap water. To no
surprise, the water in the
Solo cup had frozen by the
next morning.
The next date was Saturday, January 7, 2017.
Nighttime
temperatures
were forecasted to drop
below freezing again during the night so I had time
to construct a betterdesigned experiment.
I spared no expense conducting the second experiment—I used four 16 oz.
capacity Solo cups plus
the added expense of a
higher water bill from the
water used to fill the
cups! The first cup of water was placed out in an
open area on the patio.
The second cup was
placed a few inches from
a brick wall on the patio.
The third cup of water
was placed under the
canopy of a 15-foot tall
loquat tree growing near
a wood fence. The fourth
cup of water was placed
under the dense canopy
of a Blue Plumbago shrub
which was still flowering.
While I have no delusions
about submitting the
findings of my rather rudimentary experiment to
a revered scientific journal for publication, the
findings nevertheless can
provide some insights to
home gardeners on what
happens when a cold
Dr. William Johnson is a
horticulturist with the
Galveston County Office
of Texas A&M AgriLife
Extension Service. Visit
his website at
http://aggiehorticulture.tamu.edu/
galveston.
News column printed in
the Galveston Daily
News, The Post, and
other Galveston County
Newspapers.
Microclimates in the Landscape
Page 2
snap rapidly arrives after winter
weather conditions have been
fairly warm and balmy.
So what were my findings? The
surface of the water in the cup
placed in an open area of the patio was frozen to a depth of nearly
3/4 of an inch by the following
morning. The surface of the water
in the cup placed on the patio a
few inches from a brick wall had
only formed a paper thin layer of
ice on the surface. The ice was
easily broken with a gentle push
of my finger.
None of the water in the cup
placed under the evergreen loquat tree was frozen. The same
observation held true for the water in the cup placed under the
dense green canopy of a Blue
Plumbago shrub.
What are the implications of this
study? There can be subtle microclimates in a given area. Microclimates are the little weather variations from one side of a hill to another, from one street to the next,
and even within different sites in
the same yard. The presence or
absence of shade, wind exposure,
a water garden (or the Gulf of
Mexico), and even a nearby brick
wall or under the canopy of tree
or shrub can influence a microclimate. South facing brick walls
warm up earlier, reach higher
temperatures and have greater
variations in temperature than
north facing brick walls, due to
exposure to the sun's rays.
I described my agony with moving my cold sensitive plants indoors before the arrival of the
first cold snap earlier this month.
The first to be moved inside were
the plumeria plants since they are
very sensitive to cold temperatures. Of course, my Aggie Maroon plumeria was the first to be
moved followed by other varieties of plumeria.
when thin layers of ice are extruded from long-stemmed plants
under certain cool weather conditions. Frost flowers are so-named
because the thin layers of ice are
often formed into exquisite patterns that curl into "petals" that
resemble flowers.
By the time I had moved the
fourth plumeria, I was debating
the merits of moving yet another
large plumeria. The fifth and remaining plumeria was almost 6
feet tall so I decided to leave it
outside against a nearby brick
wall. Remarkably, the plumeria
sustained only minor damage to
two growing tips.
The formation of frost flowers is
dependent on freezing weather
conditions occurring when the
ground is not already frozen.
When those conditions exist,
plants can still draw water from
their roots up into their stems.
However, when that water reaches the stem, it quickly freezes because of the cold air. Because the
outer wall (epidermis) of plant
stems is thin, ice crystals that
form will push their way out
through the stem's walls.
The occasional cold snap made
many gardeners scramble to protect their cold sensitive plants.
Tropical and subtropical plants
can be used effectively in the
landscape, but they must be protected or replaced when necessary. The best idea is to plant a
good balance of tropical and winter hardy plants, so that your
landscape is not totally devastated in the event of extremely cold
weather.
Frost Flowers
The cold snap in early January
provided an additional and quite
rare spectacle known as frost
flowers, I’ve only read about frost
flowers (also known as ice castles,
ice blossoms, and ice ribbons).
Frost flowers aren't real flowers
at all. They are natural ice sculptures that sometimes take on the
form of flowers.
Some people describe them as
looking like spun glass or cotton
candy. A frost flower is formed
Depending upon the structure of
the plant's stem, the ice crystals
may form thin strands like a ribbon or in thin curling sheets.
When these ribbons and sheets
join together, they can create a
shape like a flower petal.
Although frost flowers are stunningly beautiful, they're also incredibly delicate. As the sun rose
that morning and the temperature started to warm, the frost
flowers melted away and vanished in an instant —but not before I could grab my camera and
take some photos.