|Some 8.6 million poinsettias were grown in Canada in 2011.
It is extremely important that we all do our very best to give the consumer the best possible poinsettia. Plant abuse anywhere in the marketing chain will ultimately show up in the final consumer setting – whether it be a hotel lobby, mall display or home living room.
I like the concept that each poinsettia plant should be handled as if it were the one you would take home for Christmas. Every poinsettia consumer deserves such treatment.
HOW GROWERS AFFECT POSTHARVEST QUALITY
■ The grower’s responsibility in postharvest care is to provide the best poinsettia possible at the proper stage of development, free of insects and diseases, and with root medium low in soluble salts.
|Dr. P. Allen Hammer.
Fertilizer salts should be reduced before shipping. However, it is not desirable to completely eliminate fertilizer application, just reduce the rate to half or quarter the rate used during early production.
Completely eliminating fertilizer application can result in lower leaf yellowing in the postharvest environment. Poinsettias can also receive chilling injury when exposed to 50 F or less for as short as a two-hour period of time. Chilling injury can cause epinasty as well as leaf loss in the most severe case.
TRANSPORT IN UNIFORM, NON-STRESSFUL CONDITIONS
■ Transporting plants in unheated trucks in the north and uncooled trucks in the south can significantly reduce poinsettia quality. Certainly a general guideline is that poinsettias do much better when placed in a uniform, non-stressful environment, avoiding too high or too low extremes in temperature, light and water.
Although bract necrosis (also called bract edge burn) is not a problem in modern poinsettia cultivars, I have observed some recurrence in recent years.
Growers experiencing bract necrosis can apply weekly sprays of 400 ppm calcium from calcium chloride beginning at first colour to eliminate the problem. Spray the bract leaves to runoff, making sure all the bract tissue is covered.
I do not recommend a wetting agent from fear of phytotoxicity, although other researchers have recommended a wetting agent to improve coverage.
Growers who have experienced any bract necrosis should spray plants with calcium as insurance. Use a ‘reagent’ grade of the chemical calcium chloride Dihydrate (CaCl2 • 2 H2O) to make a 400 ppm calcium spray solution. (1.47 gm of calcium chloride dihydrate/litre water or 55.6 gm/10 gallons water or 1.96 oz./10 gallons water)
PROVIDE RETAILERS WITH HANDLING INSTRUCTIONS
■ The poinsettia grower should also provide handling instructions to retailers. Those instructions can include: upon receiving plants, unpack and unsleeve them immediately.
Poinsettias left in the sleeve become droopy. This epinasty is often caused by ethylene production from the sleeving process. The longer poinsettias are sleeved and the higher the temperature above 65 F, the greater the droopiness problem.
The plants generally recover from epinasty in a couple of days when placed in a lighted area at 65-75 F if the sleeving period was longer than a couple of days.
Poinsettias should be placed in bright light at 60-65 F. They should, however, not receive direct sunlight under postharvest conditions.
The plants should be kept out of hot or cold drafts. A heat duct or outside door should not expose the plants to sudden changes in temperature. At no time should poinsettias be stored in an unheated or uncooled area.
Poinsettias are fragile. Rough handling will bruise the bracts and cause stem and leaf breakage. Poinsettia plants cannot be handled like hard goods.
GIVE THE PLANTS PLENTY OF ROOM
■ Also, be sure to provide adequate spacing in the display area. Plants should not be spaced so close together that the bracts from one plant rub against the bracts of an adjacent plant.
And even if you think you have no or little control on how the retailer handles the poinsettia plants, written handling instructions included with shipments will never hurt.
Dr. P. Allen Hammer is involved with product development and support with Dümmen U.S.A. He is professor emeritus of floriculture, Department of Horticulture, at Purdue University.