Indices de Maturité
Standard chrysanthemums are normally harvested fully open, or nearly so, and pompons are harvested with the most mature flowers fully open. Harvesting too early may result in the failure of the flowers to open. However, chrysanthemums can be harvested as quite tight buds and opened satisfactorily with simple bud-opening solutions. Bud-cut standards can be harvested when the inflorescence is about 5 cm across or greater and opened into full-sized flowers. 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. Stems should be cut (with a knife, shears) at least 10 cm above the soil line to avoid taking woody plant tissue. Pinched spray chrysanthemums can be pulled from the soil and then cut to the correct length. Leaves are removed from the lower third of the stems. Proper rehydration is vital for the good vase life of chrysanthemums that have been stored or shipped long distances. Remove chrysanthemum bunches from the boxes, re-cut stems (remove about 1 inch), and place in a good rehydration solution. Educate workers and customers to accept flowers that are from two-thirds to three-quarters open as these flowers will last longer than tighter harvested ones.
Grading and Bunching. Standard chrysanthemums are graded by length, and packed individually. Spray types are graded by length and bunched. Standards or disbuds of equal sizes are graded into groups of 10 or 12. Each bunch of 5-8 spray chrysanthemums should be sleeved with plastic 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 nets over spider mums in the greenhouse before the buds open.
Manipulation et stockage post-récolte
Chrysanthemums should normally be stored at 0-1°C. Bud-cut standard chrysanthemums harvested when the bud is 3 inches across can be stored up to 2 weeks and 4 inch buds for up to 3 weeks at 32-1°C. Bud-cut stems that are held in cold storage beyond the recommended time can develop flat-topped flowers. Fully mature blooms can be stored dry (wrapped in polyethylene) for 3 to 4 weeks at 0°C. Storage at 0-1°C should not exceed 2 weeks. Yellowing of leaves can occur at 5°C in the dark but is less likely to occur at 1°C.
Chrysanthemums are not sensitive to ethylene.
Pretreatments
Stems should be placed in a rehydration solution, or water containing a germicide soon after harvest if they are not to be packed immediately. Immersion in solutions of the cytokinin 6-benzyl adenine has been shown to be effective in preventing premature leaf yellowing in some spray cultivars that are prone to this problem. This treatment is not yet used commercially. Bud-harvested flowers can be opened in fresh-flower solutions containing 2-3% sugar (higher concentrations damage the leaves) at 15 to 20°C with 16 hours per day of normal room-intensity light. Physan® is a common, effective germicide, but it discolors the stem portion in the solution; therefore only 3 to 8 cm of solution 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 are 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 has similar beneficial effects.
Packing
Chrysanthemums are normally packed in standard horizontal fiberboard boxes. Standards are packed individually, and often a layer of wax paper separates each row of flower heads.
Special Considerations
The main postharvest problems for chrysanthemums are premature foliage yellowing, wilting, and the failure of the flowers to fully open. Yellow foliage is cultivar specific and is caused by poor production, excessive or improper storage, and preservative solutions used at higher than recommended concentrations. The bottom portion of some mum stems can be woody: make sure these stems are cut above this woody tissue in order to facilitate water uptake, delay wilting and extend end-user life.
Désordres
Description
Dendranthema x grandiflorum Less important than formerly, but still an important cut flower, chrysanthemums (which come in a wide range of colors and forms, including standard and spray, or pompon) 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. Chrysanthemum is Greek for “golden flower.”