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Due to
the overwhelming response to the article “Preservation of Cut
Flowers” (Timely Topics, November, 1999), the subject is extended to
better satisfy the needs of the Pinellasian flower- loving
citizenry. In Pinellas County, long-stemmed roses, carnations,
mums, lilies, orchids, anthuriums, and other specialty cut flowers
are always in high demand. These blooms are prized for their
attractive shapes, gorgeous colors, and delightful fragrances and
are used to express deepest feelings at birthdays, anniversaries,
weddings, and even at funerals as a sign of remembrance and respect.
Therefore, one must employ strategies to prolong opportunities for
enjoyment of these floral gems. Fresh cut flowers are highly
perishable and tend to lose their aesthetic appeal in a relatively
short time if they are not appropriately cared for. Factors
responsible for these changes are both physiological and
environmental. This article presents the best ways to extend the
vase life of cut flowers.
Water:
Hard water, like tap water, is
regularly used in a vase solution for cut flowers. Hard water
contains minerals which make it alkaline. Alkaline water does not
move readily through cut flower stems and can substantially reduce
vase life. One can overcome this problem by using distilled or
de-ionized water or by acidifying the water. Commercial flower
preservatives usually contain enough acid to acidify most hard
water.
Cut flowers have a high
surface-to-volume ratio. As such, they lose moisture much more
readily than many other perishable commodities. To prevent this
loss, keep flowers at a relative humidity above 95%. This
micro-climate could be maintained by applying a fine mist with a
squirt bottle and keeping flowers away from heated surfaces or open
lights.
Cut flowers readily wilt but can be
rehydrated without difficulty if there is no obstruction to water
flow. Water moves through whole plants by a negative pressure
generated by evaporation of water from the leaves. When cut flowers
do not take up water, the cause can usually be traced to one of the
following: air embolisms, poor quality water, bacterial plugging,
and physiological plugging. Water is transmitted in the stem via
very fine tubes and is always under tension. When a stem is cut,
tension is released and a small bubble of air – an embolism – enters
each conducting tube. These bubbles lodge near the cut and will
restrict water flow to the flower when it is placed in a vase of
water. There are three ways to remove embolisms: (i) hold stems
under water and remove about one inch; (ii) acidify the vase
solution to pH 3.2 - 3.5; or (iii) heat the vase solution to 104°F.
Shelf life of cut flowers can also be
improved by adding sugar to vase solutions. However, sugar enhances
growth of fungi and bacteria, but these organisms could be
controlled by inclusion of a couple drops of bleach into the
solution. Fungi and bacteria, as well as substances they produce,
can rapidly clog the fine tubes of the water conduction system. For
this reason, it is important that flower vases be cleaned regularly
and that vase solutions be treated with biocides – chemicals which
prevent growth of micro-organisms.
When a flower stem is cut, the cells
at the cut end may attempt to close (suberize) the wound. In
nature, this response might help prevent infection; but in cut
flowers, such physiological plugs can restrict water flow and thus
shorten vase life. Regular recutting of stem ends prevents the
suberization effect.
Temperature:
Flowers are alive even when excised from the mother plant. Like
animals, they need to breathe or respire. The respiration rate of a
product determines its transit and post harvest life; the higher the
temperature, the greater the respiration and vital heat increase.
Reducing the flowers’ temperature dramatically reduces respiration,
growth and aging. The optimum storage temperature for most commonly
cut flowers is close to 32°F.
However, chilling sensitive crops such as anthuriums, tropical
orchids and ginger flowers cannot be kept below
50°-54°F.
Food:
Many flowers are best harvested at the bud stage. Stored starch and
sugar from leaves and petals provide the energy for flower opening.
This is why good growing conditions, proper nutrition, and high
light to build food reserves are so important to post harvest flower
quality. Quality and vase life of many flowers can be further
improved by supplying more food – sugar – after harvest. Sugar is
routinely used to open bud-cut flowers before distribution and is
included in most flower preservatives.
Ethylene gas:
Ethylene gas is a naturally-occurring plant growth regulator
produced in high concentration by ripening fruits, vehicle exhausts,
and cigarette smoke. However, certain flower crops, especially
carnations, die rapidly if they are exposed to minute concentrations
of ethylene gas. Therefore, arrange flower positioning to minimize
ethylene exposure. Ethylene effects can also be prevented by
holding the product at low temperatures and by treating very
sensitive commodities (carnations) with silver thiosulphate salt
(STS).
Maturity and
Harvest: As mentioned
previously, many cut flowers can be harvested in the bud stage and
opened after storage. Buds, of course, must be physiologically
mature. At that stage, harvested buds can be opened fully and have
a satisfactory display life. Flowers should be harvested in the
early morning when temperatures
are lower and plant water content
is high. At no time should you place flowers on the ground. Such a
practice is a fruitful source of bruising and fungal infections.
Handling: The most
important key to quality maintenance of cut flowers is careful
handling; Tender Loving Care! Bruising and other mechanical damage
not only detract from the appearance of the product but are good
avenues of entrance for decay organisms.
For futher information, you can contact Dr. Alleyne at
(727) 582-2100 or attend an interactive workshop on the suject
matter at Long Center; Belcher Road at 11:00 a.m., May 23rd, 2000. |
