The most likely causes of a dying agave plant (Agave spp.) for homeowners are its growing conditions. Agave is often grown indoors where its growing conditions can be controlled, but it is also grown in outdoor gardens in U.S. Department of Agriculture plant hardiness zones 6 through 9. Agave plants that lack the sunlight they need, proper soil drainage, and are suffering from overwatering can easily become infested with fungus and pests.
Agave needs full sun, at least 6 hours of direct sunlight a day. Watering should be minimal. Because they are desert plants, agaves planted outdoors and in the ground rarely need water, except in extreme drought conditions. When the outdoor temperatures rise above 100 F, provide agaves with 1 gallon of water per hour for 2 to 4 hours through drip irrigation once a week. Indoor and outdoor potted agave plants should be watered only when the top inch of soil is dry. Provide enough water to the soil to make the soil moist. Plants also require fast draining soil because if it does not drain quickly it can cause the agave to rot and die. Potted agave needs to be planted in cactus soil available at most nursery stores. For agaves planted in the ground, add up to 25 percent pumice to the surrounding soil to create proper drainage. Avoid adding fresh or un-composted manure to the soil because its high salt content will damage the agave’s root development.
Anthracnose is a disease that affects agave plants. It’s caused by a fungus that occurs when an agave is overwatered and grown in damp conditions with not enough sunlight. The fungus is identified by the lesions it causes on the leaves and the orange to red spores found within these lesions. To save an infected agave plant, remove all leaves showing lesions and spores. Properly dispose of the leave and avoid overhead watering. Water the soil only when needed.
A common pest of the agave plant is called soft scale (Coccid species). These small scale insects attack stressed plants by attaching themselves to the leaves and sucking out the plant’s juices. To get rid of them, separate the infected agave from other plants and begin nurturing the plant back to health with proper watering, sunlight and soil drainage. If the infection is severe, treat the infect plant with imidacloprid found in 2-in-1 Plant Spikes by Bayer Advanced Garden. A spike is pushed into the soil and as the imidacloprid is released into the soil, the agave takes in the pest control and kills the scale bugs that are feeding on the leaves.
Death After Flowering
It is natural for most varieties of agave to die after flowering. Some of the agave varieties will produce offspring from the base of the plant to replace itself after expiring. The Octopus agave (Agave vilmoriniana) produces offspring on its flower stalk which are removed and replanted. It takes the agave about 10 years before it produces a flower and many times, agaves that are grown as indoor houseplants will not flower.