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Green-seeds.com:
flowers & ornamentals: articles
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Chyrsanthemum
Recommendations for Maintaining Postharvest Quality
Michael S. Reid and Linda Dodge Department of Environmental Horticulture,
University of California, Davis, CA 95616
 Description
The second most important of the three major cut flowers, Chrysanthemums
(both standard and spray) have a long postharvest life when properly handled.
The chief postharvest problems in these flowers are failure to draw water
(which results in premature leaf wilting) and leaf yellowing.
Maturity
Chrysanthemums are normally harvested fully open, or nearly so. It has
been shown, however, that these flowers can be harvested as quite tight
buds and opened satisfactorily with simple bud-opening solutions. Bud-cut
standards can be harvested at stage 2 (inflorescence about 2" across)
or at stage 3 (inflorescence about 3 1/2" across) when ray florets are
just beginning to unfurl, or at stage 4 (inflorescence about 5" across)
when fresh weight is about half that of fully developed inflorescences.
Buds cut tighter than stage 2 develop smaller flowers at full bloom and
are difficult to open. Stems should be placed in water containing a germicide
soon after harvest. (Use 25 ppm silver nitrate in solution or a 10 second
to 10 minute dip in 1000 ppm silver nitrate followed by good quality water
that is low in salts.) Spray varieties can be harvested when most of the
petals on the most mature flower are still upright. The flowers can be
opened after storage or transportation.
Harvesting
Stems should be cut (with a knife, shears, or the specially-designed comma)
at least four inches(10 cm) above the soil line to avoid taking woody
plant tissue. Pinched pompons can be pulled out of the soil, and then
cut to correct length. Leaves are removed from the lower third of the
stems.
Grading & bunching
The Society of American Florists has suggested the following grades for
fully open standard chrysanthemums:
|
Grade
name
|
Fancy
|
Standard
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Short
|
|
Label
color
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Blue
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Red
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Green
|
|
Minimum
diameter
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5½"(14cm)
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4¾"(12
cm)
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4"(10
cm)
|
|
Minimum
length
flower + stem
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30"(76
cm)
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30"(76
cm)
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24"(61
cm)
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Spray
chrysanthemums:
Pompons are graded into 8 to 12 oz. bunches containing several stems.
Standards or disbuds of equal sizes are graded into groups of 10 or 12.
Each bunch of 5-8 pompons should be sleeved to prevent flowers from becoming
entangled. Standards and spider mums can be wrapped individually with
thin wax paper to avoid bruising and entangling florets. Some growers
place individual nets over spider mum buds in the greenhouse.
Pre-treatments
Stems should be placed in water containing a germicide soon after harvest.
Silver nitrate provides a very satisfactory treatment but is rarely used
commercially (Use 25 ppm silver nitrate in solution or a 10 second to
10 minute dip in 1000 ppm silver nitrate followed by good quality water
that is low in salts). A more practical alternative is 5 ppm hypochlorite
(1 ml Clorox in 10 liters of water) or 100 ppm PhysanÒ ; these are excellent
germicides but may cause some stem bleaching. Where rehydration is a problem,
pulse treatments with detergent solutions (0.02% Triton-X100) have been
found useful.
Chemical solutions
Bud-opening. Bud-cut, standard chrysanthemums should be placed in a bud-opening
solution containing 2 to 3% sucrose and a germicide. Physan is a common,
effective germicide, but it discolors the stem portion in the solution;
therefore only 1 1/2 to 3 inches (4-8 cm) of solution depth should be
used. After the buds are open, the injured portion of the stem can be
removed. Silver nitrate at 25 ppm + citric acid at 75 ppm is very effective
but more expensive to use than Physan. Silver nitrate is, however, absorbed
into the stem and becomes a lasting germicide throughout the life of the
flower. HQC at 200 ppm may also be used as a germicide. Prevention of
leaf yellowing. Immersion in solutions of the cytokinin 6-benzyl adenine
has been shown to be effective in preventing premature leaf yellowing
in some pompon cultivars that are prone to this problem. This treatment
is not yet used commercially.
Storage
Chrysanthemums can be stored dry for 3 to 4 weeks at -0.5° C (31° F).
Storage at 2-3° C (36-38° F) should not exceed 2 weeks. Yellowing of leaves
can occur at 5° C (41° F) in the dark but is less likely to occur at 1°
C (34° F). Proper rehydration is vital for good vase life of chrysanthemums
that have been stored or shipped long distances. Remove chrysanthemum
bunches from the boxes, recut stems (remove about 1 inch) and place in
40° C (104° F) water containing 0.1% Tween 20 and 75 ppm citric acid.
This solution brings back turgidity within 2 hours if the room is cool
and the light is subdued. After the stems are rehydrated, they can be
moved to water containing 100 ppm Physan and placed in a cool room. It
is possible to use a solution containing 5 to 10 ppm sodium hypochlorite
(bleach) instead of Physan. Solutions containing these chlorine compounds
should be replenished every 2-3 days. Sugar is not necessary in the vase
solution, as it is not beneficial to open chrysanthemum flowers.
Ethylene sensitivity
Chrysanthemum flowers are not affected by ethylene, nor do they produce
it. Exposure to ethylene may accelerate leaf yellowing.
Rates of Respiration
Remains to be determined.
Response to CA
Our data show that controlled atmospheres are neither injurious nor beneficial
in long-term storage of chrysanthemums. Anoxic conditions destroy the
flowers.
Freezing Injury
Freezing will occur at temperatures below 0.8° C(30° F) Symptoms include
water-soaking and collapse of leaves and ligules (petals).
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