S06 - Session P1 - Evaluating indoor acclimation of floriculture plugs

Authors: Celina Gomez, Marlon Retana *

Limitations in environmental control during greenhouse propagation of hard-to-root plugs often lead to slow rooting, inconsistent growth, poor quality, and mortality, all of which result in significant loss of profits for young-plant growers. Acclimating floriculture plugs indoors using controlled environments could help reduce shrinkage (transplant loss), cut down cropping cycles, and improve uniformity during greenhouse finishing. The objective was to compare shrinkage and growth of Chrysanthemum , Lavender , and Sedum unrooted cuttings and Heuchera tissue-cultured plants acclimated indoors using broad-spectrum white light-emitting diodes (LEDs) (70 +- 6 µmol·m ‒2 ·s ‒1 for 20 h·d -1 ) and fog or in greenhouse (GH) with mist. Heuchera and Sedum acclimated indoors for 4 and 7 weeks, respectively, had lower shrinkage (6% and 58%) than those in the GH (11% and 90%). Regardless of environment, there was no shrinkage in Chrysanthemum and Lavender after 3 and 4 weeks of acclimation, respectively, but plugs were shorter indoors than in the GH. In contrast, Heuchera and Sedum were 47% and 41% taller and produced 52% and 90% more shoot dry mass, respectively, when acclimated indoors compared to the GH. Across species, indoor-acclimated plugs produced 10% to 23% longer roots and had 16% to 88% higher quality roots than those in the GH. However, Lavender plugs produced more and larger leaves and had 41% more shoot dry mass in the GH than indoors. The opposite trend was measured for Sedum , which also had a higher root mass fraction when acclimated indoors. Results from this study show the potential to reduce shrinkage and improve quality and growth of Heuchera and Sedum with indoor acclimation, both of which are often considered hard-to-root young plants. In contrast, fewer benefits were measured with Chrysanthemum and Lavender , which are less delicate young plants.