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zhanao deng university of florida breeds sun tolerant caladium and quality tubers

Caladium - What's New

by Mary Jasch

The main part of Zhanao Deng’s job is breeding new varieties of caladium, gerbera daisy, lantana and nandina. In caladium the focus is on new colors, better greenhouse performance for growers and better garden performance for gardeners.

“I am particularly interested in better sun tolerance and better improvement in bulb yield, quality and branching habit,” says Deng, ornamental plant breeder and associate professor of environmental horticulture, University of Florida. “We also work to increase disease resistance for tuber producers in the greenhouse. In the garden, disease is not a problem.”

A tuber branches out with several minor side pieces from a large central piece though some have similar size pieces. The more branches, the more colorful leaves a plant will have.

Breeders recognize three groups of caladiums but commercial growers generally recognize two. They combine lance-leaf with strap-leaf types, though the true strap-leaf is long and narrow and lance-leaf reminds of a jet with rear engines. “In the past the strap type didn’t yield well. Newer varieties yield better so popularity for them is rising,” Deng says. Today, growers are producing more strap caladium.

Three groups of caladium:
- Fancy-leaf: large and heart-shaped with two prominent lobes, each with a prominent vein
- Lance-leaf: spear-shaped with two smaller basal lobes
- Strap-leaf: one narrow, long leaf blade with one main vein, no obvious basal lobes

Large, fancy-leaf caladiums tend to have fewer leaves of varying sizes while lance-leaf and strap caladiums have numerous leaves of similar size. Deng is looking to breed new varieties that produce multiple leaves of similar size so the plant is fuller.

Strap-leaf caladiums perform the best in full sun. They and lance-leaf types handle environmental stresses such as drought, wind and sunburn better than fancy varieties. “Fancy-leaf tend to wear if moisture is low but strap and lance types can tolerate a lower moisture table and windy conditions,” Deng says.

According to Deng, over 95% of caladium tubers bought in the U.S. and 40 other countries are Florida bred and grown, amounting to 50 to 70 million tubers a year sold. His research objectives are novel foliage characteristics, tuber yield and branching and foliage sun tolerance to meet the needs of gardeners and the commercial market.

So how to tell if a plant is sun tolerant? Read the label, Deng says. “Overall, all varieties tend to be good, sun tolerant in the northeast because the temperature is not hot. When caladiums are planted in Florida in April and May, it is very hot and dry with bright sun – a leaf-burning combination. It’s not so in the northeast.”

Caladium is a good container plant because the tubers tend to sprout quickly and the plant shows color for many months. Although tubers are available, Deng recommends buying plants instead because our season is shorter and rooted, potted caladiums transplant well. “The tubers and roots are there. The tuber can support the plant. They’re supposed to be easier.”

If you’ve been discouraged in the past by seemingly fragile caladiums, don’t be anymore. Caladiums are adaptable and grow in anything from sandy loam to clay soil. They like moisture so water them a few times a week. Err on the side of over-watering. In nature, this aroid grows along stream banks and forest edges in northern South America and Central America.

Dr. Deng’s Tips:
Choose vigorous varieties.
Buy “jumbo” size tubers to get a jump start indoors
Choose a sunny spot
Plant out when soil temperature is at least 60 degrees
Fertilize with NPK numbers the same (e.g. 10-10-10 like Osmocote)

“These vigorous varieties in the Northeast have several months to grow. They will produce more leaves and have a better color display in the garden.”

Fancy-Leaf: Tapestry, Garden White, Red Flash, Carolyn Whorton, Royal Flush, Freida Hemple, Pink Cloud, Aaron, Moonlight, Strawberry Star, Candidum, White Christmas, Blizzard, White Queen, Fannie Munson
Strap (and Lance)-Leaf: Cherry Tart, Sweetheart, Red Ruffles, White Ruffles, Gingerland, Pink Symphony, White Wing

Dr. Zhanao Deng
** All photos courtesy Zhanao Deng

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published May 31, 2013

Photos to enlarge

Zhanao Deng in a Florida caladium grower's field

Strap-leaf Cherry Tart

Florida Blizzard fancy-leaf

Garden White fancy-leaf

Strawberry Star fancy-leaf

Summer Pink fancy-leaf

Summer Rose fancy-leaf

Tapestry fancy-leaf

Testing caladium in the greenhouse, some with aroid spathe flower

Field testing caladium

Caladium tuber

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