University of Vermont Extension
Department of Plant and Soil Science
Summer News
Article
FRAGRANCE IN
THE GARDEN
Dr.
Leonard Perry, Extension Professor
University of Vermont
Fragrance, or scent, in plants was
important historically in gardens, particularly in "grandma's garden"
and Victorian gardens. Once again this
trait of plants is becoming important in gardens, especially "cottage
gardens". Fragrance is complex and has had some interesting uses in the
past other than merely aesthetics.
Fragrance is an elusive quality, in
that it may be fleeting, and change over time.
Scents are detected in small quantities (often parts per billion) by
the
human nose. They are actually the reaction of certain cells in the nose
to
volatile compounds emitted by essential oils in plant parts.
These oils may come from roots, stems,
leaves, or most commonly from flowers.
Scents are usually described in
relation to everyday items with an odor, such as spices, flowers,
fruits, and even
unpleasant ones such as perspiration.
Scent is subjective, and is described by each person as either good or
bad. Whether you feel a scent is good or
bad depends on personal likes, closeness or emotion. What smells
pleasant at a distance may be overpowering
at close range. Several dozen emotional
responses to flower scents have been described by scientists.
Scents actually have a function,
usually for pollination by insects. The lighter colors of whites, pinks
and
yellows have a pleasant but faint fragrance if any. These colors
usually attract moths and
butterflies for pollination, which see rather than smell.
Composite (daisy) and umbel (Queen Anne's
lace for instance) flowers often smell unpleasant, as these odors
attract flies
for pollination. Self-pollinating flowers that need no insects
for pollination, or flowers attracting bees by sight rather than smell,
often
have no fragrance. New highly bred cultivars
of flowers, often of annuals, likewise may not have fragrance.
Some plants may use scents as
protection from insects, or as protection from drought in hot, arid
climates. From the latter plants, the
thick volatile compounds we smell provide a protective layer around
leaves. The old English custom of covering brick
walls with sprigs of rosemary for cooling has been supported by modern
research. Rosemary has 74 times the
cooling effect of fresh air (thyme has 68 times the cooling effect,
lavender 60
times).
In historic times, lack of
sanitation whether from lack of daily bathing to lack of proper garbage
disposal, led to many foul odors. Herbs known as "strewing herbs"
were used to mask room odors by strewing or scattering about the floor
to emit
nice smells when walked upon.
Plants, and particularly herbs, were
used to either cover body odors as perfumes or provide medicinal
scents. Herbs were worn on the body, clothes or
carried as pomander balls. These uses
have been supported by modern research.
Cinnamon oil kills typhoid germs in 12 minutes and other essential
plant
oils kill them in less than 50 minutes.
Attar (essential oil) of roses has seven times the antiseptic (germ
killing) strength of carbolic acid, while oil of thyme has 12 times the
strength.
Fragrant plants are best placed
along walks and garden edges where they can be brushed against (for
leaves such
as herbs) or smelled, next to buildings or patios where the warmth
brings out
the scents, and in enclosed spaces where the scents wont be blown away
by
winds.
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