Horticulture Principles and Practices

Temperature and Humidity
Wilting reduces the vase life of cut flowers. To reduce respiration and water loss, flowers
should be held at temperatures between 0 and 7°C (32 and 45°F) immediately after
harvesting until they are ready to be used. A relative humidity of about 90 percent should
be maintained. Beading and droplets of water on flowers indicate excessive humidity, a
condition that predisposes flowers to fungal attacks such as the gray mold caused by
Botrytis.
Water
After harvesting, flower life depends on the availability of good-quality water and the
capacity to absorb it. Hard water is harmful to cut flowers, as are fluoride, sodium, and
sulfate salts when present in high concentrations. Whenever possible, cut flowers
should be placed in warm (43°C [110°F]) deionized and distilled water of acidic reaction
(pH 3 to 4). The pH of water can be lowered by adding citric acid to it. Acidic water
not only improves water uptake but also has antiseptic properties, reducing infection of
the cut surface, which is known to clog the xylem vessels and prevent water absorption.
Passages are also blocked by trapped air bubbles. To correct these problems, flower
stems should be recut under warm water using a sharp cutting instrument before being
set in a vase or arranged for display. Some species, such as poppy and dahlia, require
a flame treatment in which the cut surface is passed over a flame for a very brief period.
This treatment hardens the sap. The milky sap that oozes from plants such as poppy
clogs the stems of other species held in the same container unless flame treated. The
leaves on the part of the stem that will be submerged in water in the vase should be
removed. Depending on the moisture status, rehydration may take between thirty and
sixty minutes to restore plants to full turgidity. Flowers that are purchased from a store
or transported over a long distance often need rehydration. Flowers obtained from the
home garden for use indoors can be maintained fresh by placing them in water immediately
after cutting.
Nutrition
The nutrition of plants during growth is critical to the success of flowers after cutting.
Flowers must be harvested at the right time, which is when they have accumulated enough
sugars and starches to open and sustain them after cutting. During rehydration, sucrose
may be added to the holding water to extend vase life and improve flower qualities.
Commercially formulated floral preservatives that contain pH adjuster, biocide, wetting
agent, food source, and water can be purchased from a local nursery store. Homemade
concoctions such as 1 tablespoon of corn syrup plus 10 drops of household bleach in a quart
of warm water may be used. Also, one part of soda (lemon-soda) plus two parts of water
was developed at the University of California to extend vase life. These preservatives
work because the sugar is nutritious and the lime reduces the pH of the water to suppress
bacterial growth.
Ethylene Reduction
Ethylene is a by-product of gasoline or propane combustion and is emitted through vehicles’exhaust
systems. More importantly, this chemical is a natural plant growth hormone
involved in several physiological processes such as fruit ripening, seed maturation,
aging, and wound healing. Certain flowers are ethylene sensitive (Table 24–4). In the
presence of excessive amounts of the gas, flowers of these plants deteriorate rapidly.
Ripening fruits and vegetables produce large amounts of ethylene and as such should not
be stored or transported with cut flowers. Treatment with a commercial preparation of
silver thiosulfate reduces the effects of ethylene on cut flowers.
24.2 Culture 685