The plants are watched carefully during the seasons of picking, of which there are three or four each year. The April picking yields the choicest crop of leaves, and only the youngest leaves and buds are taken.[35] A single plant rarely yields more than four or five ounces of tea yearly. Each acre of a tea-garden yields about three hundred and fifty pounds. After picking, the leaves are partly crushed and allowed to wilt until they begin to turn brown in color. They are then rolled between the hands and either dried very slowly in the sun, or else rapidly in pans over a charcoal fire--a process known as "firing." The former method produces _black_, the latter _green_, tea. The color of the latter is sometimes heightened by the use of a mixture of powdered gypsum and Prussian blue. In the black teas the green coloring matter of the leaf is destroyed by fermentation; in the green teas it remains unchanged. The greater part of the Chinese tea designed for export is packed rather loosely in wooden chests lined with sheet-lead, the folds and joints of which are soldered in order to make the cover both air-tight and moisture-tight. A full chest contains seventy-five pounds of tea. The Japan product is also packed in moisture-tight wrappers, the original parcels being usually ten-pound, five-pound, and pound packages. Similar devices are used in preparing the India and Formosa teas for ocean shipment. The chief tea-producing countries are India (including Ceylon) China, Japan (including Formosa), and Java. A successful tea-garden is in operation near Charleston, S.C. A small amount is grown in the Fiji and Samoan Islands. The Ceylon and Formosa teas take a very high rank. [Illustration: AREA OF TEA PRODUCTION] Great Britain and her colonies consume the bulk of the tea-crop. The average yearly consumption per person is eight pounds in Australia, six in Great Britain and Cape of Good Hope, and more than four in Canada. In the United States and Russia it is less than one pound per person. Before the opening of the Suez Canal, in 1869, most of the crop for the English market was despatched by way of Cape of Good Hope. So important was it to get the consignments to London without loss of time, that fast clipper ships were built especially for carrying tea. Since the opening of the canal the crop has been shipped mainly by the Suez route. A part of the tea required for the United States reaches New York by way of the Suez Canal, but the movement is gradually changing since the building of the fast liners that now ply between Asian and American ports. These steamships carry it to Seattle, or to Vancouver, whence it is distributed by rail. The increased cost of shipment by this route is more than offset by a gain of from five to seven days in time.