Amongst the most difficult of pollination requirements to meet, Dioecious plant species produce male and female flowers on seperate trees, requiring the presence of at least one male and female plant to cross-pollinate and produce. Some dioecious plants have guaranteed female and male plants seperately available (such as Pistachios and Kiwifruits), however, with many diecious plant species (such as Imbe or Bignay) they are only sold as seedlings of unknown gender. In cases of unknown gender seedlings, it is advisable to acquire at least three plants to increase the chance of acquiring both male and female plants. Female plants will produce fruits while male plants will pollinate flowers and are able to pollinate a large amount of female plants by themselves. While the minimum two plants required may make them unsuitable for space concious gardens, they are well-suited to large gardens where they can form a feature such as hedge or row of trees.
Hortiforum 