Seasonal variation in pollen viability and flowering times identifies
the importance of selecting donor cultivars and how they are
most effectively deployed in individual orchards. The objective is
to produce high and consistent yields that do not inhibit the flower
induction process so, unless fruit are thinned chemically, this is best
accomplished with a pollination deficit. The problem is to define
and achieve such a level. Security suggests the advantage of using
more than one donor cultivar, perhaps three or four, because a
single best pollinizer is rarely identifiable. In small orchards, it is
desirable to interplant a second cultivar with a proportion not lower
than 10% of the main cultivar (Tombesi, 2003). In hedgerow systems,
harvesting is simplified by planting of pollinizers in individual
rows, although in large orchards, individual blocks may contain
single cultivars. Nevertheless, it is important to indicate that
pollination design for SHD orchards is still a largely unresolved
question that must address not only the number and identity of
pollinizers but also their proportion and distribution.