Dr. Dave Clark and Team Release New Coleus Cultivar
Coleus (Solenostemon scutellarioides, now Plectranthus scutellarioides) plants are used as annual bedding plants for the landscape and mixed containers in Summer gardens across North America Europe and Asia. Coleus plants are popular to commercial growers and landscapers because they are easy to propagate and provide fast and reliable color that makes their businesses profitable. Coleus plants are also popular with home gardeners because they are easy to grow in both full sun and partial shade conditions, and require less maintenance than many other annual garden plants.
The coleus breeding program at the University of Florida in Gainesville, FL was initiated in 2003 with an emphasis on developing new clonally propagated cultivars that are profitable for producers, and perform well in consumer gardens with little or no care. We have focused on developing new cultivars with novel leaf colors and shapes, increased vigor, and branching, and we do that by conducting greenhouse trials and field trials under demanding environmental conditions. We conduct greenhouse trials under “lush” conditions that push the plants to grow as fast as possible with high amounts of light, high fertility and high temperatures. We use these conditions because it allows us to quickly see growth habits and vigor characteristics, and also observe plant phenotypes under conditions where greenhouse pathogen pressure is highest. Our field trials at Citra, FL are planted in full sun in sand beds with reflective silver plastic mulch in May each year with drip irrigation and a minimal amount of slow-release fertilizer added at planting. Our field trials at Gainesville, FL are planted in 30% shade in sand beds in May each year with drip irrigation and a minimal amount of slow-release fertilizer added at planting. We use these “lean” growing conditions in our field trials because we want to screen for plants that grow
vigorously and consistently for minimalist gardeners and because coleus produces a better seed crop under “lean” conditions than “lush” conditions, which is useful for making open-pollinated seeds for our recurrent mass selection program.
Desirable characteristics that continue to be in demand a decade after our first commercial introductions are 1) foliage color stability in sun and shade, 2) consistent well branched plant habit, and 3) late flowering. Improved plants with interesting foliage colors in both full sun and shade conditions allow for more versatile garden use and more color choices for gardeners. Superior well-branched plant habit is important throughout the production chain to the consumer because it allows for production of a large number of vegetative propagules, and translates into more manageable plants for producers during culture and shipping to retail outlets. Once planted in the garden, these plants require less management over a long season of growth. Late flowering is a desirable characteristic because early flowering triggers senescence of the lower leaves and decreases foliage quality of coleus. Floral induction often slows vegetative growth, and increases landscape maintenance with manual dead-heading and plant replacement, which is vital to landscape contractors. Late or ‘no flowering’ genotypes with good branching and stable foliage color that have been developed at UF have performed well in commercial markets, and continue to attract interest from US, European and Asian gardeners. The following UF genotype ‘UF14-24-1’ was selected because it has all of these desirable traits in a singular novel plant.