There are seven species of tropical perennial plants in the botanical genus Caladium, but ask gardeners and they usually talk of brightly colored, leafy plants sometimes called elephant ears, angel wings or hearts of Jesus. Growing from tubers, the plants display their heart-shaped or arrowhead-like leaves when temperatures and soil are warm and humidity and soil moisture are high.
Caladium plants are native to tropical areas of northern South America but modern varieties are the result of decades of genetic breeding. These hybrids are often assigned the botanical name Caladium x hortulanum or Caladium bicolor.
Members of the aroid family, caladiums grow from underground plump and horizontal stems called tubers. They are wrinkly and brown in color, unlike the tubers of potatoes. The leaves are borne on upright herbaceous stems. Their shape is heart-like with points or arrowhead-shaped with the leaf stem attaching to the back center of the leaf blade. Leaf texture is thin and papery to more leathery and smooth. Genetic breeding leads to plants with amazing coloration on leaf veins or in the inter-vein areas, including tones of green, white, silver, lavender, pink and red. Flowers rarely occur on the plants except where they grow in tropical regions. The green to ivory blooms are hidden by the leaves, upright and not ornate. They comprise a tightly bound cloak-like spathe surrounding a finger-like spadix.
The hundreds of varieties of caladiums are generally classified into two types: fancy-leaf or strap-leaf. Fancy-leaf caladiums produce large leaves on petiole stems that range in height from 12 to 30 inches, according to North Carolina State University. The leaf blades are thin and papery in texture and are prone to damage from hot sunlight rays. Strap-leaf types produce leaves smaller than fancy-leaf caladiums. The strap-leaves are more arrowhead-shaped or lance-like and are thicker, making them more tolerant of direct sun rays. Stem petioles are usually less than 16 inches tall. The tubers of strap-leaf types tend to produce more leaves per tuber than those of fancy-leaf tubers.
Caladium tubers or bulbs are usually grown as seasonal plants in the warm summer months in U.S. Department of Agriculture hardiness zones 3 through 10. Tubers are planted in moist soil that drains well and is rich in organic matter like compost. The tubers need warm soil, at least 55 degrees F but ideally a minimum of 70 degrees, in order to produce leaves and maintain them across the growing season. Fancy-leaf caladiums should be planted in shady locations in bright, indirect light with minimal exposure to direct sun rays. Strap-leaf types can be grow in partially shaded to nearly full sun exposures as long as soil is moist. While growing, water and fertilize freely as long as temperatures remain above 70 degrees.
Consult plant labels to learn of specific light tolerances for each caladium variety, as there is great variation. Tubers may be left in the ground to overwinter in USDA zones 9 and warmer, but are best lifted after the first fall frost and stored in a cool, dry spot indoors over the winter. Even in tropical regions, the caladium often goes dormant in seasonal droughts or in the cooler winter months.
The diversity in leaf shapes and colors as well as mature stem heights allows gardeners to use caladiums to create stunning design compositions. Juxtapose flowering annuals or perennials next to caladiums to either contrast or mimic the leaf colors. The caladiums may be grown in massed sweeping clusters as a ground cover under shade trees or in mixed flower beds. Or, plant the tubers in large containers and mix in other flowering plants.