Native only to the rainforest slopes on the Atlantic Ocean side of Guatemala, the corn palm (Chamaedorea nationsiana) gains its name from the clustered fruits that resemble tiny corn cobs, but with black kernels. It has feathery fronds on single upright stalks that mature 8 to 10 feet tall. Although not hardy to winter cold, its small size makes it easy to protect from frosts in USDA hardiness zones 10 and warmer.
Corn palm is closely related to a group of small shade-tolerant rainforest palms known as parlor or bamboo palms (Chamaedorea spp.). Therefore, whether grown outdoors or indoors as a house plant, provide the plant with indirect light, never prolonged exposures to hot, direct sun rays. Grow it under a tropical shade tree or several feet back from a bright window so direct rays never reach the fronds across the calendar year.
Plant corn palm in a loam or sandy soil that is moist but well draining and rich in organic matter. The soil's pH must not be overly alkaline (over 8.0). These characteristics mimic the conditions of its natural habitat of organic matter atop limestone soils in Guatemala.
During the warmth of the growing season, from spring to early fall, keep the soil evenly moist but never waterlogged or saturated. Provide 1 to 2 inches of rainfall or irrigation weekly when temperatures are above 80 degrees Fahrenheit. From autumn to early spring, reduce watering to no more than 1 inch each week. House plant containers must not sit in a basin of pooled water as it promotes root rot and depleted oxygen levels in the soil.
Outdoors the use of organic matter like compost and bark mulches improves soil quality and provides trace nutrients to the corn palm across the year. Maintain the mulch layer at a 2- to 4-inch depth. Utilize a slow-release granular fertilizer formulated for palms, scattered around the palm base and outwards to 3 feet away in spring, summer and fall. Follow product label recommendations for dosage rates. House plants can be fed with liquid fertilizers (10-10-10 with micronutrients), but leach out quickly. Do not fertilize during late fall and winter months. Alkaline soils may lead to nutrient deficiencies in foliage as seen by yellowing old and new fronds. Sprinkle one or two handfuls of epsom salts (magnesium sulfate) around the palm base over the mulch anytime to prevent this dilemma.
Corn palms most actively grow when temperatures are warm and humidity high, so refrain from removing healthy green fronds that are producing food. Allowing any dying fronds to fully yellow and brown before pruning them off results in nutrients being pulled and relocated to other parts of the plant. Do not cut off the top of the palm's trunk or stem, as this will stop further development of new fronds and leads to plant death within a year. Old flower clusters or fruits can be trimmed away with a scissors or hand pruners at any time. Only the female flower clusters become the corn cob-like fruiting structures after being pollinated.
Occasionally spidermites may plague the undersides of palm fronds, especially in indoor environments that are warm, low in humidity and lacking air movement. Insufficient light may cause stressed palms to host scale infestations on frond stems. Mealybugs may also appear in indoor environments. Wipe away these pests with a cloth rag soaked in warm soapy water. Spraying frond undersides can deter spidermite infestations.