In areas with prevailing winds almost daily, windbreaks will help to increase bee activity and therefore increase fruit set. They will also help to reduce fruit drop during the strong "east winds" which often occur during the fall months.
A windbreak will provide lateral protection at orchard tree level for about four to six times its height. The trees should be planted at a right angle to the direction of the prevailing wind.
For a very tall windbreak, Eucalyptus globulus (blue gum), Lombardy poplar (Populus nigra italica) or a hybrid willow sold under the name Austree (Salix hybrid) are ideal. The Lombady poplar and Austree have less intrusive roots than Eucalyptus, which is preferable in some situations. They also are deciduous, so they will permit better air flow during frost periods. Tall-growing varieties of avocado, such as Bacon, also make very acceptable windbreaks. They may also have the advantage of providing cross-compatible pollen for the Hass variety, which may increase fruit set in an all-Hass orchard.
In areas with only occasional winds, windbreaks may actually be a disadvantage as they often reduce the vigor of the first two rows of trees nearest the windbreak, due to competition for water, fertilizer, and rooting space.