Effect of Vermicompost-amended Media on Container-grown Miniature Roses

An experiment was conducted to evaluate earthworm castings (vermicompost) as an amendment to a peat-based potting media for container-grown miniature roses. Bare-root roses of Crackling Fire, Feisty, or Hot Tamale were planted in 3-gallon containers of potting media containing 0%, 5%, 10%, 20%, or 40% vermicompost and maintained in an outdoor nursery area during the growing seasons of 2009 and 2010.  Height, width and quality ratings for flower quantity and quality, foliage quantity and quality and vigor were collected monthly from May through October.  Chlorophyll content was measured using a SPAD meter. Volume was derived from height and width measurements.  Each cultivar responded very differently to the vermicompost treatments.  Crackling Fire - Height and volume increased during the growing season.  Width increased during the season for all treatments, but the increase was less as the vermicompost content increased from 0% to 40%. Flower quality ratings declined during the peak summer months, but improved during the fall.  Chlorophyll content decreased as vermicompost increased from 0% to 40%.  Feisty - Height, width and volume for Feisty increased during the season for all media treatments and declined as vermicompost increased. Flower quality ratings declined throughout the growing season.  Chlorophyll content was greatest during the peak summer months for all treatments, but declined as vermicompost increased. Foliage quality and quantity was greatest in May for 0% followed by 40%, but whereas roses grown in 0% vermicompost declined through the season, roses grown in 40% vermicompost rebounded in the fall.  Vigor followed a similar pattern with some fall improvement for both 0 and 40% treatments. Hot Tamale – Height and volume increased through the season with growth decreasing from 0% to 40% vermicompost in May. However, by October plants increased in height and volume as the vermicompost content increased. Plant width increased both from May through October and as the vermicompost content increased from 0 to 40%.  Flower quantity and quality decreased linearly and chlorophyll content increased linearly through the season. Foliage quantity and quality and vigor slightly decreased from 0% to 40% vermicompost in May, but maintained quality well until late summer when quality declined through fall with the greatest decline at 0% compared to 40%.