Digging In - Advice on Bird of Paradise

By Scott Aker
Special to The Washington Post
Thursday, February 19, 2009

Q I have a bird of paradise plant that I started from seed last spring. During the summer it grew rapidly in its eight-inch pot and is now 24 inches high. I keep it in a sunny location in the house, where temperatures are 73 degrees during the day and 65 at night.

Four bottom leaves have curled and died, and the remaining leaves are beginning to show the same symptoms.

It is growing in potting soil with fertilizer, and I let it go fairly dry before watering. I use liquid fertilizer biweekly at the recommended rate. I have installed a humidifier, though I can't seem to get the relative humidity over 25 percent.

Should I repot into a larger container and use a different type of potting soil? Needless to say, this plant is very precious to me.

A You are applying far too much fertilizer. Fertilizers are salts such as potassium phosphate and ammonium nitrate. I suspect the plant is reacting to a buildup of these salts in the potting soil. You should not feed the plant while it winters indoors.

Flush the salts out of the soil by watering the plant. Wait half an hour for the salts to go into solution and then flush again with an additional gallon of water. This is best done in the bathtub or shower where you can allow the salt-laden water to go down the drain. You can also give the leaves a rinse at the same time. After the second watering, wick the excess moisture from the pot by placing it on an old towel, with good contact with the drain holes. Place the pot (and towel) on a chair and drape the towel into the tub. Allow the plant to sit for an hour or two to get rid of extra moisture before returning it to its sunny window.

You also need to find a cooler environment for it. Bird of paradise is a subtropical plant native to South Africa. It grows to five feet tall and produces a rosette of leaves with long stalks. It is well-adapted to drought. Although it should never encounter freezing temperatures, it requires significantly cooler and drier conditions in the winter than in the summer. A sunny, unheated room is ideal. During the winter, night temperatures should be in the low 50s and, by day, below 70 degrees. It will be much easier to maintain the necessary humidity in these cooler temperatures.

In early spring, repot the plant into a container at least 14 inches in diameter. After the plant reaches maturity, don't be in a hurry to repot it again -- it is more likely to bloom if kept rootbound. Grow the plant outdoors from late April to early October in full sun or light shade, fertilizing it monthly with a liquid fertilizer.

Scott Aker is a horticulturist at the U.S. National Arboretum.

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