Agave americana, commonly called the Century Plant, is a succulent desert plant native to Mexico. It can grow outdoors year-round in USDA plant hardiness zones 8 to 10. The largest of the Agaves, mature plants range from 5 to 7 feet (1.5 to 2.1 m) tall with 8- to 12-foot (20 to 30 cm) spreads. Century Plant makes a dramatic accent plant with its blue or blue-gray leaves, black spines, and showy, yellow-green flowers. Despite its renowned hardiness, Century Plant can still suffer from a few cultural, disease, and pest problems.
Century Plant can tolerate various cultural conditions as long as it is planted in fast-draining soils. Poor-draining soils make the plant susceptible to the fungal pathogens that cause root rot. This Agave can survive down to 15 degrees Fahrenheit (-15 degrees Celsius), but the broad, fleshy leaves will suffer from freeze damage if the temperature drops below freezing for several hours. Freeze-damaged tissue turns black, dries out, and looks unsightly. The damage can't be repaired, but most Century Plants will recover. Prevent freeze damage by covering the plant with a light cotton sheet when your area expects a freeze.
Although Century Plant isn't associated with any serious disease problems, root rot can be problematic in poor-draining or overly moist soils. Root rot causes wilting, stunted growth, and discolored leaves. Unfortunately, this fungal infection cannot be treated once it occurs. Anthracnose is another occasional problem that occurs when fungal pathogens thrive in overly moist soil conditions. This disease causes lesions to form on the leaves, with red or orange spore masses developing inside the sores. Remove any anthracnose-infected plant tissue promptly to prevent the disease from spreading.
For the most part, Century Plant doesn't have serious pest problems, but there is one exception. Root rot typically goes hand-in-hand with agave snout weevil infestations. Adult females chew through to the plant's base to lay their eggs in the infected plant tissue. The larvae hatch and burrow their way into the heart of the plant. Severely infected Century Plants look wrinkled or shriveled and emit a foul odor. The rotting plant tissue eventually collapses, and the plant dies. Controlling Agave snout weevil is difficult, but spraying the plant's base with a broad-spectrum insecticide in the spring often helps prevent infestations from occurring.
Avoid Century Plant problems by providing your plant with the best possible growing conditions. These succulents perform best when planted in fully sunny areas, although they can handle some light shade. Century Plant grows best in sandy or gritty soils with dry to medium moisture. These drought-tolerant plants only need occasional watering in dry summer weather to remain healthy. Give the plant plenty of room to grow and make sure it is planted away from foot traffic. The sharp spines can poke you and cause your skin to swell painfully.