Caladiums, recognized by their large, vibrant foliage, are popular tropical plants for adding color and texture to Houston’s shade gardens. Successful cultivation relies heavily on precise regional timing and adherence to specific climate requirements. Houston’s warm climate (USDA Hardiness Zone 9a/9b) requires specialized advice to ensure the bulbs thrive.
Optimal Planting Time in Houston
Planting Caladium bulbs too early is the most common mistake, as these tropical tubers are extremely sensitive to cold. They require warm soil to break dormancy and begin robust growth, making the soil temperature the single most important factor. The ground must be consistently above 70°F (about 21°C) for the tubers to sprout vigorously; planting in cooler soil can cause the bulbs to rot before they even emerge.
For Houston, the optimal planting window is typically from late March through May. While planting can begin around the beginning of April, the exact timing shifts each year based on local weather patterns. It is prudent to use a soil thermometer rather than relying solely on a calendar date to confirm the necessary warmth.
Planting Caladium Bulbs for Success
Once the soil temperature is adequate, preparing the planting bed correctly ensures the bulb’s long-term health. Caladiums require a well-draining medium, rich in organic matter, as they will rot quickly in soggy conditions. Amending the planting site with compost or peat moss before planting helps to establish the necessary loose structure.
The bulbs should be placed 1.5 to 2 inches deep in the soil for proper root development. Space the tubers approximately 8 to 12 inches apart, depending on the mature size of the specific variety. The knobby side, which contains the “eyes” or growing points, must face upward when placed in the ground. For gardeners seeking a head start, bulbs can be started indoors in containers four to six weeks before outdoor conditions are warm enough for transplanting.
Maintaining Caladiums in Houston’s Climate
After planting, the challenge shifts to managing the intense heat and humidity characteristic of a Houston summer. Most traditional Caladium varieties thrive in filtered light or full shade, mimicking their native habitat beneath the jungle canopy. Newer, sun-tolerant varieties are available, but even these typically benefit from protection from the harsh midday sun.
The leaves of any Caladium variety can suffer damage, sometimes called “melting,” which appears as brown-edged holes if they receive too much direct sun exposure. Consistent moisture is necessary, as Caladiums will quickly wilt during Houston’s dry, hot spells. The soil should be kept evenly moist but never allowed to become waterlogged, which prevents tuber rot.
Container-grown plants may require daily watering during the peak summer temperatures. Those in the ground can be watered less frequently, especially if a layer of mulch is applied. To support the continuous production of large, colorful foliage, a balanced liquid fertilizer should be applied every four to six weeks. Fertilize after watering to avoid burning the roots.