Indoor citrus trees deliver fragrance, fruit

Here's a delicious idea that will brighten your winter-dulled spirits: Grow a citrus tree!

Nothing revives the senses more than inhaling the sweet, sunny aroma of citrus blossoms and fruits. And you don't need to have a California or Florida address to do so—anyone can grow citrus trees indoors. There's a wide selection from which to choose, including many dwarf hybrids bred specifically for indoor culture. All they require is a sunny window, an appropriate pot, fertile soil and some simple TLC.

You'll be rewarded with attractive and productive plants with leathery green leaves, pretty blossoms and colorful fruit. Citrus trees can often blossom and fruit at the same time, making them especially prized as houseplants. And while you won't get a huge harvest, what you do produce will be a visual and tasty treat.

Citrus limon ‘Meyer Improved'

Give them a proper planting

Citrus plants need air at the root zone, so choose porous pots or tubs—unglazed clay or terra cotta, cedar or redwood—with drain holes. The pot diameter and depth should be about one-third to one-half the height of the plant to give the roots plenty of room in all directions. If you have a 24-inch-high plant, for example, it should be planted in an 8- to 12-inch pot.

Prepare a soil mixture of equal parts light, well-drained commercial potting soil and clean, coarse sand. Add ¼ cup of bone meal per gallon of soil mixture to give new plants a boost.

Pot plants as soon as you receive them; then prepare to be patient. It can take six to nine months for lemons and limes to go from flowering to harvest on 3-year-old trees. Other citrus varieties can take up to 12 months.

Lime ‘Bearss Seedless'

Provide a good environment

All citrus plants need sun, preferably 8 to 12 hours daily, to stay healthy and productive. Place the plant in a south or southwest window with unobstructed light for best exposure. Because citrus plants grow more slowly in the winter, they can tolerate slightly lower light conditions during that season. Where natural lighting isn't available, use artificial lighting.

Keep soil moist but not soggy with regular, deep watering. Citrus plants thrive in a rich, acidic soil, so fertilize three times during the growing season—March, June and September—with a fertilizer formulated for citrus. Withhold the fertilizer over the winter, and take care not to overfeed as citrus plants burn easily from too much feeding.

Citrus thrive at temperatures between 55°F and 85°F; don't let temperatures go below 50°F. As warm days arrive in the spring and the danger of frost passes, gradually acclimate citrus plants to an outdoor deck or terrace (just as you would harden off a seedling) where they'll ultimately be in full sun. In the fall, as cool weather approaches but before frost arrives, move the plants back indoors.

Make the move in stages—first for about a week in shade outdoors, then to a cool, bright window with a southern exposure. Sudden changes in light, temperature and humidity can harm or even kill citrus.

During the winter, heated rooms may need additional humidity. Place potted plants on pebbles in water-filled saucers to improve air flow and humidity. You can also mist the foliage with water to help increase humidity.

Pollinate and prune

While outdoor plants are pollinated by insects, indoor citrus plants must be hand-pollinated to produce flowers and fruit. To do this, use a small clean paintbrush or cotton swab, making sure to transfer some of the pollen from the anthers to the pistils (see illustration, above).

Under the right growing conditions, your plants will grow rapidly, so it's important to prune them lightly to maintain their attractive shape. The best time to do this is in the winter when their growth has slowed. You should also repot plants every other year to give roots adequate room.

Keep them healthy

Citrus plants are susceptible to a few common houseplant maladies. Keep watch for brown scale or white citrus scale. Both can be controlled with commercially formulated insecticidal soap spray. If spider mites or mealy bugs appear, give the plants a cleansing shower with a hose or in a bathtub.

Leaf drop or the failure to flower or fruit usually results from extreme changes in light or temperature conditions or improper watering. Don't throw out the plants, however. Attending to their needs often brings them back from the brink.

Grapefruit ‘Dwarf Redblush'

8 citrus to try

Look for these citrus plants at your local garden center in the spring or buy them year-round from mail-order companies. If you purchase mail-order plants, keep in mind that they're typically smaller and, therefore, might take longer to bear fruit.

Choose dwarf varieties when they're available to keep pruning chores to a minimum.

Buddha's hand citron (Citrus medica var. sarcodactylis, shown above): Resembling a cluster of fingers, this fruit is prized for its thick, fragrant rind that makes a flavorful zest. Its inner white pith isn't bitter like most citrus, and its fruits have little flesh or juice.

Calamondin (x Citrofortunella microcarpa): Its bright orange, walnut-size fruits are like tart and tangy tangerines. Lush, dark green leaves and fragrant, white blossoms make this a superb houseplant.

Dancy mandarin (Citrus reticulate ‘Dancy'): Like other mandarins, this dwarf variety doesn't need as much heat to ripen as true oranges.

Grapefruit ‘Dwarf Redblush' (Citrus x paradise ‘Dwarf Redblush', above): This newer dwarf variety produces fewer seeds and has a richer blush-red color than previous cultivars. Fruit lasts well on the tree with ripening starting in winter and continuing through spring.

Kaffir lime (Citrus hystrix): This plant's unique, double-lobed leaves and the rind of its fruit are often used in Thai cooking. The juice from the fruit is excellent in limeade and tea.

Lime ‘Bearss Seedless' (Citrus aurantifolia ‘Bearss Seedless' also ‘Dwarf Bearss Seedless'): This densely branched variety produces large, juicy fruit from winter to early spring.

Meyer lemon (Citrus meyeri ‘Meyer' or Citrus limon ‘Meyer Improved'): Meyer lemons, long touted by chefs and gourmets, are a little sweeter, a bit more fragrant and less acidic than other lemons. Meyer lemon plants are prolific and easy to maintain as houseplants—the best choice for gardeners just starting to grow indoor citrus fruits.

Nagami kumquat (Fortunella margarita, square photo at top of story): True kumquats are oblong and somewhat tart, but these fruits are nearly round and perfectly sweet.

sources | Citrus Trees Online, Lakeway, TX, citrustreesonline.com; Clifton's Flower & Garden Center, 888-209-4356, Porterville, CA, buyplantsonline.com; Four Winds Growers, Winters, CA, 877-449-4637, fourwindsgrowers.com; Logee's Greenhouses, Danielson, CT, 888-330-8038, logees.com; Monrovia, Azusa, CA, monrovia.com; White Flower Farm, Litchfield, CT, 800-503-9624, whiteflowerfarm.com; Willis Orchard Co., Cartersville, GA, 866-586-6283,willisorchards.com.

Weldon Burge is a garden writer in Newark, Delaware. Photos by Bill Johnson, Josh McCullough, Monrovia, Mark Turner and White Flower Farm. Illustration by Elara Tanguy.

Citrus limon ‘Meyer Improved': Meyer Lemon flowers aren't just beautiful. They're deliciously fragrant!