Alocasia amazonica is a hybrid plant whose parent species, Alocasia sanderiana and Alocasia watsoniana, are rain forest plants native to Asia. It is widely available as a houseplant and is popular because of its striking foliage, with dramatically shaped leaves that are deep green to greenish black, contrasting with prominent white veins. Growth comes from an ovoid corm. Like all alocasias, Alocasia amazonica is particular about its growing conditions. If a proper rain forest-like environment is not provided, yellow Alocasia leaves and even death of the foliage may occur.
This plant's hybridizer named it after his business, the Amazon Nursery in Miami, Florida. There is much confusion about the correct name and status of this plant. Common names for it include African Mask Plant, Jewel Alocasia and Alocasia Alligator. A smaller-growing form is called Alocasia Poly or Polly.
Water Stress Promotes Alocasia Leaf Loss
Alocasia amazonica prefers evenly moist but not waterlogged conditions. Soil can be allowed to slightly dry between waterings, so that the soil is dry just an inch or two from the surface but still moist beneath this. Yellow Alocasia leaves result if the plant is allowed to dry out. Leaves can turn color and die, and the plant can go into dormancy. If it dries out completely, the corm dies. The corm will stay alive once it has entered dormancy, but some soil moisture has to be maintained in order for it to survive and regrow when conditions are right.
Perfect Soil for Healthy Leaves
The forest floor where the parent plants grow has open, loose soil with lots of organic matter. Typical houseplant mixes do not work well for Alocasia amazonica because they are not well-draining enough. A recommended mix contains about 30 percent of a well-draining soil, 20 percent peat and 40 percent orchid bark with charcoal. Plants growing in improper soils can stay too wet, resulting in leaf yellow Alocasia leaves and dieback and eventually a fungus infection of the roots that can result in the death of the plant.
Intense Light Causes Yellow Alocasia Leaves
Bright, indirect light is preferred. Alocasia amazonica can tolerate quite bright light since parent species are found growing in almost direct sunlight. Too much light or exposure to direct sun, especially in warm ambient temperatures, leads to leaf yellowing if not actual scorching. Conversely, Greener House Nursery advises that insufficient lighting will cause your Alocasia amazonica to quickly display large yellow and brown spots on the leaves due to stress.
Maintain a Warm Environment
This plant does well in temperatures that are comfortable for people, between 60 to 75 degrees Fahrenheit. It should not be exposed to temperatures below 55 degrees, which will cause yellowing of leaves and dormancy. Exposure to cold drafts will cause similar symptoms.
Humidity Wards Off Yellow Leaves
A humidity of above 65 percent is needed for this plant. To supply this without keeping the soil too moist, the plant can be grown on a tray filled with pebbles with a layer of water beneath the pebbles. Greenery Unlimited recommends frequent misting of this plant. If humidity becomes too low, leaf loss will occur.
Sometimes Yellow Leaves Are Normal
New growth comes at the center of the plant, which grows from an ovoid corm. Bloomscape advises that as the plant becomes older and fuller, an outer leaf can occasionally turn yellow and dry up. The leaf is simply old enough to be replaced, and should be trimmed away to keep your plant looking tidy. As long as the new growth is healthy and the plant is vigorous, this is normal.