2017 ASHS Annual Conference

The objective was to determine the effect of soil moisture content (SMC) during poinsettia (Euphorbia pulcherrima ‘Freedom Red’) greenhouse production on plant quality and postproduction longevity. Treatments included two SMC levels (20% and 40%) applied in four timing of application combinations. Total production (TP) time was 14 weeks in which vegetative production (VP) occurred from week 33 to 39 and reproductive production (RP) continued from week 40 to 47. The timing of application treatments groups were: I = TP at 40% SMC; II = TP at 20% SMC; III = VP at 40% + RP at 20%; and, IV = VP at 20% + RP at 40%. After 48 h simulated shipping in the dark, plants were evaluated for five weeks in a simulated retail environment with three packaging treatments: (1) N = no packaging; (2) C = pot cover only; and, (3) CS = pot cover and sleeve. Growth index (GI), photosynthesis (Pn), leaf greenness (SPAD), leaf thickness, and petiole thickness were measured weekly. Bract number, leaf number, internode length, and dry weight (DW) were measured at week 39, 42, 45, 47. Starting at week 42, group II and III plants had lower Pn than group I and VI. Plant DW was not affected by SMC during vegetative growth but was reduced in group II and III compared to group I and IV starting at week 45. Leaf thickness was not affected by SMC treatment but petiole thickness was higher in group I and IV comparing to group II and III starting week 43. Group II and III had shorter internode length and smaller growth index than group I and IV at the end of greenhouse production. Plants in group II or III were more compact and had earlier bract coloring without reduction in bract and leaf number. During postharvest, CS packaged plants had reduced leaf number due to leaf abscission and the lowest SPAD reading, regardless of SMC treatment. Plants in group I had the lowest bract number after five weeks of postharvest, and group I and IV packaged with CS had the lowest live stem number. In summary, reducing SMC to 20% during total production or during the reproductive stage reduced water usage and produced more compact plants with greater postproduction quality.