The two commonly grown coffee trees are Arabica and Robusta. Most specialty coffees are Arabica, whereas cheaper coffees on the store shelves are Robusta blended with some Arabica to improve taste and flavor. Robusta trees are hardier and resistant to frost and diseases. Most high quality Arabicas are produced in central and South America and Hawaii. Eastern countries and Brazil are the major producers of Robusta. Robusta has twice the caffeine content of Arabica. Robusta flowers are cross-pollinated whereas Arabica can be self-pollinated. Robusta trees are taller and produce more coffee beans per tree. Robusta coffees are considerably cheaper than Arabicas. Good Robusta coffees have good body and pungency and are used for blends of excellent espressos.