Sikkim became a part of the Indian Union in 1975. Most of the land is mountainous, interspersed with valleys and two rivers, Teesta and Rangit. It has rare varieties of orchids and flowers. About 11,889 hectares of land are under irrigation. The economy is mainly agrarian with the principal crops being maize, rice, wheat, potato, tea, cardamom, ginger and orange. Horticulture and floriculture is being expanded. The industries located in the State are watch assembly units and manufacture of jewel bearings for water and electric metres and clocks. Small industries development is being promoted. Winters are long and severe, summers are cool and average annual rainfall is 311 cm.