Lemons: 'Improved Meyer,' 'Ponderosa,' 'Variegated Pink.' Meyer lemons are slightly sweeter than regular lemons and take on an orange hue when ripe. 'Variegated Pink' lemons have variegated foliage and pinkish fruit.

Limes: 'Kieffer,' 'Bearss' seedless. The leaves (and fruit) of 'Kieffer' limes are used in many Asian cuisines, especially Thai.

Calamondin: xCitrofortunella mitis. This small, tart, orange-colored fruit likely originated in Asia and is supereasy to care for. "It's probably the easiest citrus to grow," says Tom McClendon, contributing author of Landscaping Indoors. It's also great in lieu of lemons in lemonade.

Kumquats: 'Nagami' and Fortunella hindsii. Kumquats are tart-sweet and can be eaten whole (skin and all).

CARING FOR CITRUS
Under the proper conditions, citrus plants will thrive indoors. Here are some care guidelines. (Keep in mind that different plants have different requirements, so ask your nursery for specific instructions.)

Light: Citrus does best with 6 to 12 hours of sunlight a day. If you don't have a sunny room, supplement with a full-spectrum fluorescent grow light or solar tubes (tubular skylights that bring in natural light; see www.solatube.com). When you bring the plant outside for the summer, keep it in indirect sunlight to avoid leaf scorch and overdrying; half-day sun or filtered sun should be sufficient.

Temperature: Citrus grows best at about 65°F or above. They can survive lower temperatures, but will become quiescent below about 55°F.

Soil: Don't use ordinary garden soil for container citrus because it's too dense and doesn't allow water to drain properly. "I like to buy a cactus mix that's extremely well-draining," says citrus expert Tom McClendon. "Or I make my own with ground-up pine bark and perlite [volcanic material that both aerates the soil and makes moisture and nutrients available to the plant], which keeps it light."

Water: Keep soil moist but not soggy: Allow the top 2 to 3 inches of soil to dry before watering, and then water until it drains out of the bottom. Keep the plant out of standing water because it will get root rot, and make sure there is at least one drainage hole in the pot.

Fertilizer: Fertilize once a month with a water-soluble 20-20-20 fertilizer at half strength. An occasional spoonful of Epsom salts (magnesium sulfate) will prevent yellowing leaves.

Humidity: This is especially crucial in winter months, when most homes are extremely dry. To increase moisture, spray the foliage with water, bring the plant into the bathroom (not the tub) when you shower, use a humidifier, or place the pot atop a tray of pebbles that you keep wet.