One of the greatest needs of the semi-desert and desert areas of Africa is a fast-growing drought tolerant tree which has multi-purpose uses. In addition, nitrogen-fixing properties and salt tolerance are also useful. Nitrogen compounds in the soil encourage the growth of dryland grasses: salt tolerance is necessary as many of the areas involved have a high salinity. Felger states 'Although irrigation has made some deserts bloom, it is expensive, sometimes impractical, and it can permanently ruin the land by concentrating the salt through evaporation. He suggests an alternative: rather than trying to alter desert lands to suit water-loving crops, why not select plants which are adapted 10 desert conditions? Species of Prosopis offer all of the attributes given above yet, until recently, have received little attention. In particular, P. pallida and P. juliflora J which have been introduced to Kenya, are particularly useful. They are the subject of the investigation described in this article.