The Osyris lanceolata Hoscht. and Steudel. is an evergreen drought resistant shrub of the Santalaceae family. It thrives well in the ASALs of tropical Africa and on the margins of forests and bushlands. The mature tree species has dense heart wood that produces essential oils used in perfumery and pharmaceutical industries to make expensive cosmetics and drugs. Trunks and roots of mature preferable female trees are illegally over-extracted from the forest hence threatening the species with extinction to meet the ever rising international industrial demand. This study therefore aimed at describing the phenology and the reproductive biology of the species in Kenya. Two distinctive populations namely; Kabarnet and Kitui were considered. Onset and end dates of flower bud initiation, flower opening, fruit initiation, fruit maturity and ripening were observed on artificially pollinated flowers, anther emasculation and on control. Fruits that developed in each experiment were assessed for full or empty embryo by cross sectioning of the fruits. Flowering began in early February and September, and flowering season closed in July and December respectively. The species complete its flowering phase in 109±16 days. Assisted pollination increased the reproductive success of the trees by 39.7%.