Fertilizer Rate, Vesicular-Arbuscular Mycorrhizae, and Trichoderma Application Influenced Poinsettia Growth and Development

Vesicular-Arbuscular Mycorrhizae (VAM) and Trichoderma fungi have been attributed to improved plant uptake of macro and micronutrients and enhanced water availability. The main objective of this study was to examine the application of VAM and a commercial product, RootShield^TM containing Trichoderma harzianum, and various fertilizer rates on the growth and development of poinsettias. The study was conducted in the greenhouse in a complete randomized design with four microorganism treatments (Control, VAM, RootShield^TM, and VAM plus RootShield^TM); one soil media (Promix Bx Mycorise Pro); and three fertilizer rates (recommended rate and 50% and 25% of the recommended rate), with four replications each. Poinsettia cuttings, ‘Poi Cortez Burgundy’ (Euphorbia pulcherrima), were obtained from Greenstreet Grower, Inc. Treatments were added at the time of transplanting. The poinsettias were fertilized every three weeks. Plant height, days to color change, and shoot and root dry weights were determined. Results indicate that the VAM treatment influenced plant growth and development.  There was a significant difference in shoot dry weight.  The VAM treatment also tended to have the highest shoot height among treatments.  There was a significant difference in shoot dry weight among treatments in the recommended fertilizer rate.  There was also a significant difference in root dry weight among treatments in both the 50% and 25% recommended fertilizer rates.  There was no significant difference in number of days to color change between the treatments and fertilizer rates. More studies will be conducted to further assess the effects of reduced fertilizer rates and beneficial microorganisms on growth and development of poinsettias.