Feature Article - for release the week of  June 1, 2008

Dan Culbert - Extension Horticulture Agent

Coleus for Summer Color   

Winter and spring flower beds are often planted with impatiens or begonias that don’t do well when temperatures begin to rise.  Gardeners that appreciate masses of colorful flowering beds are always on the lookout for colorful plants that can take the heat. 

There are many heat and drought tolerant perennial flowering plants good for the long haul, but some gardeners like to choose short-term annuals for sudden splashes of color.

Coleus plants are prized for their bright foliage rather than their flowers.  They are being rediscovered and are moving from container to flower bed because they can take the heat. Coleus with these characteristics are highly desirable, but few cultivars are commercially available that have these traits.  

At the recent UF Floriculture Field Day, several new varieties of coleus were part of the bedding plant trials.  These new improved coleus were developed by UF doctorate student Penny Nguyen, and are the subject for this week’s Florida Yards column.

 

Building a better Coleus

University of Florida graduate student Penny Nguyen has spent several years developing better coleus varieties.  Nguyen works with Dr. Dave Clark, a UF horticulture professor.  Their efforts have resulted in the release of 13 new varieties of coleus.

Her breeding program focused on developing new coleus cultivars with sun tolerance and limited flowering.   Secondary goals were to look for high vigor, high branching and novel colors.

Nguyen began breeding Coleus in 2003 with 15 open-pollinated varieties.  By 2006, she had 30,000 seedlings that were ready to be evaluated. These seedlings were then reduced to 150 selections subjected to high light, high humidity and temperature, drought stress, wind stress, insect damage, competition with weeds and the possibility of diseases.

Plants were discarded if they showed low vigor, poor branching, dark or non-novel color, poor rooting, and early flowering.   Those that have made the grade are now available from Proven Winners and Ball FloraPlant.

 

The Survivors

 Growing Coleus

Coleus do best at temperatures moderately warm temperatures (50°F night to 85°F day).  At warmer temperatures, the stems will stretching and become leggy.  Cooler temperatures give more vibrant colors and slow the growth.  And, temperature changes can also affect color. New varieties were selected to avoid color changes under high temperatures.

Under moderately high light levels coleus color is at its best; low light conditions fail to bring out many vibrant foliage colors of this plant.  New cultivars were also selected for color stability under varying light levels.

Coleus grow well in containers.  Best results are produced with a standard mixture of peat & perlite.  Aim for a pH range of 5.5-6.0.  Use any balanced bedding plant fertilizer, and keep plants lightly moist at all time.  Overwatering will cause root rot.  In the landscape, be sure that the soil is moist and avoid poorly drained sites.

Best results with coleus mean a minimal amount of grooming will be needed.  Remove the top part the plant stem by pinching out the growing point – this will encourage branching.  New Coleus cultivars were selected for self branching behavior.

Flower stalks grow on the ends of Coleus stems.  These are undesirable as the plant becomes leggy and spends energy on seed production that can best be used for colorful leaves.  New cultivars were selected for late or non-flowering habits.

 

I’ve placed more information on our Okeechobee web page, http://okeechobee.ifas.ufl.edu.  If you need additional information on Coleus, please email us at okeechobee@ifas.ufl.edu or call us at 863-763-6469.  Local residents can stop by our office at 458 Hwy 98 North in Okeechobee, and visit our Okeechobee County Master Gardeners from 1 to 3 PM on Tuesday afternoons.   Go Gators!

 

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Trade  names, where used, are given for the purpose of providing specific information. They do not constitute an endorsement or guarantee of products named, nor does it imply criticism of products not named. The Florida Cooperative Extension Service - Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information, and other services to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin.  Florida Cooperative Extension Service / IFAS / University of Florida.  Larry A.  Arrington, Dean. Last update: 05/30/2008.  This page is maintained by Dan Culbert  

Coleus leaves can be big: look for the penny on the leaf of this potted plant at EPCOT.	Coleus can provide contrasting colors in the flower garden. Containers with different colors and textures can be mixed and matched.
Note the flower spikes on this coleus. They will make the plant less attractive after the small florlets fade.  Generally they are pinched off well before they develop this far.	Retail garden centers have a variety of coleus varieties in many different sized containers.  For bedding plants, choose flats of cell pack grown cuttings that can be transplanted into the flower bed.