Focus on Floriculture Vol 5 #1
For the last several years, we have received complaints from retailers and growers about droopy bracts on poinsettias (particularly the newer cultivars) after delivery to the retail shop.^ The general answer has been they were sleeved too long. A comment in the Gelger News said Rutgers blamed ethylene gas given off by the plants in the sleeves as the cause of bract droop on Supreme (1). I have long suspected shipping temperature to be more of a problem than plant sleeves. Growers have assured me that temperature Is not the cause. However, how many actually measure temperature in their trucks? Shanks (2) recommends a shipping temperature of 50-55°F. After moving some plants this year in a warm van with a cold floor, we got tremendous bract droop on some cultivars. So we conducted the following study: Poinsettia plants in 6-inch clay pots were taken from the green house (62-65° night; 70-75° day) and exposed to 50°F for varying amounts of time (30-120 minutes) in a growth chamber with 2000 foot candles of light. After removing the plants from the 50°F treatment they were placed in a room at 70-75°F with 80-140 foot candles of light. Photographs were taken at selected times to record the amount of droop. Soil temperatures were also recorded.
Keywords: ethylene gas Sleeves shipping temperature 50°F