Chinese Camellia sinensis is native to mainland China South and Southeast Asia , but it is today cultivated across the world in tropical and subtropical regions. It is an evergreen shrub or small tree that is usually trimmed to below two metres (six feet) when cultivated for its leaves. It has a strong taproot . The flowers are yellow-white, 2.5–4 cm in diameter, with 7 to 8 petals.The seeds of Camellia sinensis and Camellia oleifera can be pressed to yield tea oil , a sweetish seasoning and cooking oil that should not be confused with tea tree oil , an essential oil that is used for medical and cosmetical purposes and originates from the leaves of a different plant. Camellia sinensis plant, with cross-section of the flower (lower left) and seeds (lower right). The leaves are 4–15 cm long and 2–5 cm broad. Fresh leaves contain about 4% caffeine . The young, light green leaves are preferably harvested for tea production; they have short white hairs on the underside. Older leaves are deeper green. Different leaf ages produce differing tea qualities, since their chemical compositions are different. Usually, the tip (bud) and the first two to three leaves are harvested for processing. This hand picking is repeated every one to two weeks.