As we approach the month of\u00a0December, hopefully everything we\u00a0have done up to this time has prepared\u00a0the poinsettia for the final stage of its\u00a0growth cycle.\u00a0Bract development is near completion, the root system\u00a0is healthy and well established, and the size, tone and colour of the\u00a0leaves have been optimized by a sound fertilization program.<\/strong>\u00a0The ideal growing conditions associated with rapid leaf unfolding,\u00a0good leaf expansion, extensive root development and efficient nutrient\u00a0uptake are gradually phased out as winter approaches. Any hopes\u00a0of sizing up undersized plants are diminishing quickly as temperatures\u00a0continue to drop and daylight continues to weaken in the north.\u00a0Any attempt to optimize growth near the end of the crop by providing\u00a0additional heat or increasing the concentration of fertilizer can actually\u00a0jeopardize post-harvest quality. From now on, everything we do should\u00a0be directed towards preparing the poinsettias for the stress of shipping\u00a0and the retail environment.<\/p>\n Fertilizer and irrigation practices should now be geared towards reducing\u00a0the EC of the substrate which will lower the salt content to levels\u00a0that are more conducive to post-harvest quality. A word of caution,\u00a0however: stopping your feed program too early can lead to premature\u00a0yellowing and dropping of the lower leaves in the retail setting. A safer\u00a0approach is to gradually drop fertilizer levels to 80\u2013100 N (nitrate based)\u00a0for the last two to three weeks.<\/strong> This must be done with close monitoring\u00a0of EC levels during this final period of growth before shipping.\u00a0Many problems, like bract edge-burn and root loss, can be avoided\u00a0by simply leaching out high salts and gradually reducing the fertilizer.<\/p>\n Moving onto climate control, the goal now\u00a0is to tone and condition both the leaf\u00a0canopy and the root environment to\u00a0optimize survival during the shipping\u00a0process and the harsher conditions\u00a0of retail environments. As the\u00a0cold season has progressed, the\u00a0plants have filled in and the lack\u00a0of space has created a thick,\u00a0crowded leaf canopy. Keep the\u00a0air dry and constantly circulating\u00a0throughout the canopy as much\u00a0as possible to reduce any humidity\u00a0<\/strong>that would be conducive to\u00a0disease outbreaks. As shipping\u00a0begins, watering should be done\u00a0on demand, based on the daily\u00a0shipping routine, rather than on a\u00a0fixed schedule. Keep a close eye on\u00a0the condition of the roots, as they can\u00a0be subject to overwatering during the\u00a0shipping process. A saturated pot placed in\u00a0a pot cover can definitely create a deleterious\u00a0microclimate in a dark, sealed shipping box! Botrytis\u00a0development on the bracts and cyathia during shipment\u00a0can be a problem if latent infections are not controlled during production\u00a0or if moisture condenses on the bracts prior to or during shipping.\u00a0Just watch how fast condensation accumulates on the plastic sleeve\u00a0when a poinsettia is left on a greenhouse bench in the afternoon sun.\u00a0As for temperature control, if the crop is maturing too fast and lowering\u00a0the temperature is warranted, make sure to continue to heat\u00a0and vent the greenhouse sufficiently to eliminate high humidity and\u00a0provide good air circulation.<\/strong>
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![\"poinsettia](\"https:\/\/www.berger.ca\/en\/wp-content\/uploads\/sites\/2\/2016\/07\/raices_floresNochebuena-200x300.jpg\" "\\"Poinsettia")