A coconut palm tree (Cocos nucifera) features large, ornamental palm leaves as a houseplant but doesn't flower or produce coconuts. Outdoors, the tree is hardy in U.S. Department of Agriculture plant hardiness zones 10 through 12, grows 50 to 100 feet tall and has a 20- to 40-foot-wide canopy. Indoors, the tree grows from a sprouted coconut fruit to 5 feet tall in about five years.
Providing Proper Growing Conditions
Bright light and well-drained potting soil provide the best conditions for a coconut palm grown as a houseplant. Outdoors, the tree thrives in a full-sun site along a seashore or coastal lowland. When young, it can grow in a partially shaded site and brightly lit indoor area, such as near sunny windows or in a conservatory.
Grow an indoor coconut palm in a mixture that is 50 percent soil-based potting soil and 50 percent horticultural sand or grit. The houseplant's container must have bottom drainage holes. It should be 2 inches wider than the coconut fruit and at least 10 inches deep.
Watering and Humidifying
A coconut palm houseplant needs moist soil and high humidity. Water its soil whenever the soil surface is dry. Remove the plant's container from its drip tray, stand it where it will drain easily, and slowly pour water on the soil surface. When water flows through the pot's drainage holes, stop watering. Allow the container to drain thoroughly before putting it back on its drip tray.
Spray the coconut palm's leaves every two or three days with a fine mist of water to increase the site's humidity level. An alternative is to fill a wide, shallow tray with gravel or pebbles and water, and then stand the tree's container so its drip tray rests on top of the gravel or pebbles. Water evaporating from the shallow tray will humidify the air around the coconut palm.
Maintaining Temperature Levels
A subtropical and tropical tree, the coconut palm needs constantly warm temperatures. It grows best when daytime temperatures are 70 to 80 degrees Fahrenheit and nighttime temperatures are 65 to 70 F. In summer, when temperatures are reliably higher than 65 F at night, you can leave the tree outdoors in a warm spot that is partially shaded during daytime and sheltered from strong wind.
Take the tree indoors in late summer or early fall. Don't stand it near a heat source, which will dry out its leaves. If your house becomes colder than 65 F at night, put a cloth over the tree in the evening, and remove it in the morning.
Scale insects and mealy bugs can infest a coconut palm grown as a houseplant, but the indoor plant rarely suffers from diseases. Scale insects look like tiny shells and stick to palm leaf veins, and mealy bugs are covered in a cottonwool-like coating.
Control scale insects or mealy bugs with a ready-to-use insecticidal soap spray. Cover all the tree's parts, including its leaf undersides, with the solution. Spray the plant every one to two weeks if necessary.
Fertilizing the Plant
An indoor coconut palm doesn't need fertilizer during the first year after it sprouted from a coconut fruit, but an older tree benefits from a houseplant fertilizer. Apply a slow-release, granular, 12-4-8 fertilizer every three months. Sprinkle the granules on the soil surface; the amount of fertilizer to use depends on the width of the plant's container. For example, apply 3/4 tablespoon of the fertilizer if the container is 10 inches wide and 1 1/2 tablespoons of the fertilizer if the container is 12 inches wide. Fertilizer manufacturers' instructions vary among products, however. So follow the advice on your fertilizer's label.