Deserving of their common name, fancy-leaved caladium (Caladium bicolor) lends showy color to garden beds and borders. Its arrow- to heart-shaped leaves are streaked, splashed or mottled with pink, red, white or gray in addition to green. Many cultivars exist, usually growing 2 feet tall by 2 feet wide in U.S. Department of Agriculture plant hardiness zones 9 through 12. Plants grow from tubers, commonly called bulbs, which are dormant in the winter. For tubers to survive winter, dig and store the tubers in USDA zones 8 and lower.
Planting Directly in Beds
After all danger of frost is over, plant caladium bulbs in the garden, covering them with about 1 inch of soil. Place the tuber with the bumpy, bud side up. The buds may be difficult to see. Find the buds by running your fingers over each side of the tuber to locate the small, pointed projections that form the buds of the new stems. If it's still hard to tell which side should be up, plant the tuber on its side. Space tubers 8 to 12 inches apart, depending on the mature plant size of your cultivar -- thousands of cultivars exist. The leaves can overlap by a few inches to give good coverage.
Planting Bulbs in Pots
Especially if you live in a cold winter area that has a short growing season, start caladium tubers in pots indoors or in the greenhouse so they're already growing when you plant them outside. Four to six weeks ahead of the last frost date for your area, fill 6-inch pots to within 2 inches of the rim with a soiless potting mix such as equal parts of peat and perlite.
Placing Started Bulbs in Beds
After the tubers have rooted and the plants are growing, plant them in the garden when all danger of frost is over. Either unpot the rooted tuber and plant it in the bed at the same soil level as it was in the pot, or sink the whole pot up to its rim in the garden bed. In areas where tubers need to be dug up for the winter, digging up a pot simplifies removal -- but you'll need more storage room. You may also wish to use this method to remove tubers in mild winter areas with ample rain to protect tubers from excessive moisture, which can cause rot.
Starting Tubers in Flats
Another option is to start dormant tubers in nursery flats rather than pots, beginning four to six weeks before the last frost date. Line a nursery flat with screening or newspaper to keep the potting mix from falling through the holes and put about 1 inch of potting medium in the flat. Dormant tubers go bud side up on top of the mix, spaced closely but not touching each other. Just barely cover the tubers with more potting mix and water the flat.
Removing Rooted Tubers
When you're ready to plant the caladiums in the garden, work your fingers under the rooted tubers along one side of the flat, removing the rooted mass from the flat. After placing it on a clean work surface, gently separate each rooted tuber from its neighbors and plant in the garden, putting the top surface of the tuber 1 to 2 inches below the soil surface.
Light and Soil
Most caladium varieties develop the best leaf color in partial shade, although they will grow in full shade. Some varieties now exist that tolerate full sun, especially in areas with cool summers. Caladiums need soil rich in organic matter that drains well and is slightly acidic. Amend garden soil with 2 inches of aged compost or peat dug into the soil before planting to increase organic material.
Water and Fertilizer
With a native distribution in tropical South America, caladium needs to be kept moist but not soggy during its growing season. Caladiums need regular feeding from the period when leaves are beginning to grow to the end of its growth cycle when days shorten and temperatures cool, usually late summer. Since too much nitrogen affects leaf color, use a low nitrogen fertilizer such as water-soluble 24-8-16 applied every two weeks at the rate of 1 tablespoon for every 1 gallon of water used. Soak the soil around the plants.
As leaves yellow and die back in early fall, if you live in USDA zones 9 through 12, you can leave the tubers in the ground but withhold water during dormancy. In colder areas, dig up caladium tubers before the first frost, remove the leaves, stems and roots and let them dry for a few days in a shaded area. Store the clean, dry tubers between wood shavings or dry peat at 50 to 60 degrees Fahrenheit. If you've kept the tubers in pots, remove the pots and store them in a dry place with temperatures 55 degrees F or above for the winter.
Like other members of the Arum family, all parts of caladium plants contain substances which can irritate skin and which can be harmful if eaten. Wear gloves and protective clothing before working with the plant if you're sensitive to caladium. Leaves are useful in floral arrangements.