The genus Citrus comprises about 15 species of small trees and shrubs including those that bear lemons, limes, tangerines, oranges, and grapefruit. While still young, they make attractive house-plants because of their glossy leaves, plenty of flowers and bright colored fruits. The ripening process may take 3 months or more. Edible fruit can be expected from lemon C. Limon and sweet-orange bushes C. Sinensis.
Water moderately while they are actively growing allow the top inch of the mixture to dry out between waterings. During resting period water only enough to keep the mixture from completely drying out.
Give a high potash, tomato-type fertilizer, when in active growth, every 2 weeks. If light intensity is poor during the Winter, do not feed plants till it improves.
Move plants into containers one size larger every Spring until maximum convenient size is reached 10 inch pots or larger tubs. Thereafter an annual topdressing of fresh soil-based potting mixture will suffice.
A citrus may be propagated by a 3 to 6 inch long stem cuttings. Dip each cutting in hormone rooting powder, plant it in a small pot containing moistened equal parts of peat moss and perlite or coarse sand. Enclose the whole in a plastic bag in medium light and temperature of 15 - 21 Celcius. After rooting has taken place, six to eight weeks, remove plastic bag and water the plant moderately.
Provide at least 4 hours a day of direct sunlight. Citruses do best if placed outdoors in bright light during the Summer. Normal room temperatures are suitable. Maintain a Winter temperature of 10 - 12 Celcius.
Shorten overlong shoots of citruses by two-thirds in early Spring. Nip out growing tips at any time to encourage bushy growth.
After propagation, begin monthly feedings of half-strength standard liquid fertilizer. When roots emerge from drainage hole, re-pot and treat it as mature Citrus.
For increased humidity, stand citruses on trays of damp pebbles and mist spray occasionally.
Scientists were able to revive a flowering plant from the fossilized fruit found in the stomach of an Arctic ground squirrel who was trapped in ice around 32,000 years ago.