In the cash budgets of farm householdsin western Kenya, off-farm occupations and cropsaccount for the most important sources of income. Treeand livestock products are of secondary importance incash terms, although farmers attach great importanceto trees as a source of income because of the variousnon-monetary functions they supply. The findingspresented in this paper suggest that two variables, the domestic development cycle of households andwealth, are likely to affect the adoption pattern ofcertain introduced