COLUMBIA, Mo. - Home gardeners who want to try something different might want to grow a sour orange or other citrus tree indoors, said a University of Missouri fruit researcher.

"There are many different types of citrus trees that can be grown indoors," said Michele Warmund.

Sweet citrus trees tend to be difficult. By contrast, acid citrus species are easy to grow in containers inside and many will bear several crops of fruit each year if given optimum growing conditions, she said.

The Calomondin sour orange is frequently grown as an ornamental with its fragrant white flowers and orange fruit. Other possibilities include the Meyer or Ponderosa lemon, Tahiti or Persian limes and Meiwa kumquats. Citrus trees can be grown from seed but tend to be large trees and may take more than seven years to bear fruit.

Citrus trees grown indoors require a nursery container at least 14 inches in diameter with a loose, well-drained potting mix maintained at a 5.5 to 6.5 pH.

A half whiskey barrel also makes a good container as long as it has drainage holes drilled in the bottom.

The trees should be placed in a room kept at 55 to 68 degrees F with a southern exposure that allows for at least eight hours of bright light each day, Warmund said.

High humidity also is required in the 30 to 60 percent range. Most homes have an average humidity of only 15 to 20 percent, so a cool mist vaporizer or humidifier may be used.

Alternatively, placing the container on a pebble tray that is partially filled with water and misting the foliage frequently helps raise the humidity.

Apply a soluble citrus fertilizer formulated to maintain the medium at a slightly acidic pH once a month or use a slow-release fertilizer.

Trees require water when the top 2 to 3 inches of potting medium feels dry. Over-watering is a common cause of fruit drop.

"If you enjoy a beautiful plant, like an enticing floral scent, love to eat fruit or enjoy an unusual spice, there is a citrus tree that you can grow easily indoors," Warmund said.

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