Why was coffee farming originally done ?
These include leguminous trees of the genera " Acacia " , " Albizia " , " Cassia " , " Erythrina " , " Gliricidia " , " Inga " , and " Leucaena " , as well as the nitrogen - fixing non-legume sheoaks of the genus " Casuarina " , and the silky oak " Grevillea robusta " .