The citrus genus includes some interesting indoor plants, which produce flowers and fruit intermittently all year when conditions are right. They have glossy, deep green foliage, spiny stems, and white, fragrant flowers. Each fruit ripens slowly from green to orange or yellow’, so that there will be fruit of each color on the plant at the same time.
C. limon, from Southeast Asia and better known as lemon, will ultimately grow into a small tree up to 6 ft. (2 m high) but while small, makes an attractive indoor plant. Its flowers are tinged purple. To grow edible fruit choose a named variety.
C.l. ‘Variegata’ has leaves variegated cream and fruit striped green, becoming fully yellow. X Citrofortunella microcarpa (formerly Citrus mitis) is an ornamental orange, called cala-mondin orange, which produces fruits when still quite young. Its unripe green fruits, although bitter, are useful for making marmalade. x C.m. ‘Tiger’ has leaves edged and streaked with white.
Size: Height 4 ft. (1.2 m).
Light: Direct sunlight.
Temperature: Normal room; winter minimum 50°F (10°C).
Moisture: Keep moist from spring to fall. In winter apply enough water to prevent the soil from drying out.
Feeding: Provide with standard liquid tomato fertilizer every two weeks from spring through to fall.
Propagation: Take 4 in. (10 cm) tip cuttings, preferably semiripe with a heel, in spring or summer, and dip in hormone rooting powder. Seed will take longer to grow to flowering size.
Special needs: Increase humidity by placing the pot on a tray of moist pebbles. In warm regions, the plants can be placed outdoors in summer. Pinch out the growing tips at regular intervals to produce bushy growth.