The spring-flowering bulbs are now long finished, and all that is left is their leaves. It is time for the summer flowering plants like cannas, dahlias, lilies, tuberous begonias and Lily of the Nile to bring color to the landscape. Perhaps one of the most notable summer foliage tubers is Caladiums. The heart-shaped leaves of these tropical South American plants range in size from 6 to 12 inches in width.
Caladium foliage is also very distinctive. The midribs on the leaves provide streaks and flashes of color many times, providing high contrast with the rest of the foliage. Foliage colors include reds, pinks, whites, and greens — all in various shades and combinations. Most foliage is heart-shaped with long petioles and is considered fancy leaved. Caladiums can reach heights of up to 30 inches.
Most caladium cultivars are adapted to full shade, but many selections tolerate partial sun or early morning sun. Caladiums planted in the shade tend to have bigger leaves and want to be taller to catch the light as opposed to caladiums in direct sunlight. The color intensity can vary according to sunlight and the amount of fertilizer used. Full sun reduces the intensity of the foliage color of most cultivars. Caladiums traditionally needed protection from full sun for best growth and color, but some of the newer varieties tolerate exposure to full sun for a couple of hours daily.
Unlike the spring-flowering bulbs, tulips, daffodils, etc. which are imported into the U.S. from Holland, Caladium bulbs are the U.S. grown in Florida. Lake Placid, Florida, is considered the Caladium Capital of the World.
Caladiums add a nice tropical look to your landscape, either planted in garden borders or as container plants that add color to the patio and porch. Because Caladiums are considered true tender bulbs and are sensitive to cold weather, they should be considered annuals in our area. You can, however, save the tubers and then replant them in the spring after the last chance of frost. Caladiums can be purchased from nurseries and garden centers as already growing plants or as tubers. They will perform reasonably well in full shade, but the color may not be as outstanding.
Caladiums require warm, moist soil. A minimum soil temperature of 70°F is preferred. For best growth in the landscape, plant either the tubers or the plants in well-drained soil with a pH between 6.0 and 6.5. A 2- to 3-inch layer of pine bark mulch or compost should be incorporated into the soil to improve soil aeration, drainage, and organic matter content. Root and foliage growth will be limited unless the soil is well aerated. Also, incorporate a complete fertilizer such as 8-8-8 at a rate of 1 to 2 lb. per 100 square feet of bed area (2 tablespoons per square foot). If planting tubers, place them tubers 2 inches deep and 8 inches apart for small tubers and 12 inches apart for large tubers. Both roots and shoots emerge from the top of the tuber; place the knobby side up.
Fertilize them once a month with a balanced fertilizer like 8-8-8 or 10-10-10. Mulch with a 2- to 3-inch layer of organic material to conserve moisture and keep the soil cool. Soil temperatures over 85°F can result in leaves with more green color and less of the highly prized, brilliant colors. High levels of nitrogen fertilization can produce the same effect. Caladiums are heavy feeders of potash and phosphorus and must have ample moisture and summer feeding of fertilizer in order to produce good tubers for the next growing season. Apply 1 tablespoon of 5-10-10 fertilizer per square foot every 4 to 6 weeks during the growing season. For individual plants, use a heaping tablespoonful; for plants grown in containers, use a level teaspoon per pot. Do not allow fertilizer to contact the leaves. Water thoroughly after fertilization to prevent fertilizer burn. Caladiums are not drought tolerant and should be watered on a regular basis.
Caladiums, on occasion, will produce a bloom which looks similar to a Jack-in-the-Pulpit or calla lily. The general recommendation is to remove the bloom since it takes away energy from the foliage and reduces tuber size.
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