The 2011 ASHS Annual Conference

Rain lilies are defined by two genera: Zephyranthes and Habranthus. There are about 70 known species and more than 80 cultivars and hybrids. In 2008, Dr. Geoffrey Denny at the University of Florida Gulf Coast Research and Education Center in Balm collected three varieties of Habranthus and nine varieties of Zephyranthes with the intent to study the performance of these varieties in Central Florida. Through a partnership with Dr. Marina D’Abreau, Urban Horticulture extension agent and Master Gardener Volunteer Program coordinator in Hillsborough County, Florida, two Master Gardener volunteers – Diane Schwaninger and Roger Rixom – carried out the work directed by Dr. Denny (and subsequently by Dr. Deng) and Biological Scientist, Nancy West.

An irrigated 8’ x 32’ topsoil bed was divided into 182, 1’ x 1’ sections (7 wide and 26 deep), and the clumps of each variety were planted in a random fashion. An Osmocote Plus extended release fertilizer (15-9-12) was applied at the rate of one tablespoon per clump at the beginning of each 30-week growing season starting on May 1, 2009 and 2010. The study identified four performance criteria: frequency of flowering, length of flowering season, growth factor and resistance to climatic conditions.

Based on the data collected, the following varieties of rain lilies are recommended for Central Florida:

• Z. candida (pale pink/white, stands up well to weather, strong grower with extended prolific flowering)
• Z. grandjax (pale mauve, late prolific flowering)
• Z. traubi (white, extended prolific flowering, strong grower, wilts in rainfall)
• Z. grandiflora (purple, very large flowered, strong grower, not prolific flowering but very showy)

The study will continue through year 3 with a reduced replication (3 per variety) to make the count and measurement less labor intensive. In addition, some initial studies will commence on some more modern hybrids. At the start of year 3, approximately 1,500 Z. candida bulbs will be incorporated into a nitrogen requirement study at the Gulf Coast Research and Education Center. Several new varieties with larger and more colorful blooms have been obtained from an overseas source. A hybridization program is in its early phase to improve the bloom quality of Z. candida. The Master Gardener volunteers will collaborate with Dr. D’Abreau to develop a fact sheet and other relevant educational materials for Central Florida residents.