Almond varieties fall into specific groups within which cross-pollination will not occur. It is very important to check which variety combinations are incompatible. An updated list of the pollen-incompatible groups is included in Connell’s presentation.

There is heightened interest in recently introduced self-compatible and partially self-compatible varieties. Although self-compatible varieties will reduce reliance on bees, it will not eliminate them.  According to UC Davis almond breeder Tom Gradziel, there are a number of factors — genetic, environmental and the structure of the flower — that determine self-pollination and set. Even with self-compatible varieties, honey bees can ensure maximum set because bees consistently transfer pollen within the same flower from the anthers to the stigma of the pistil, where fertilization is initiated. However, because pollen no longer needs to be transferred between different varieties, the number of hives required will be reduced.

Harvest timing

According to Connell, in essence, when a variety reaches 100 percent hullsplit, the nuts are harvestable. In his presentation, he reviewed a table showing 100 percent hullsplit of different varieties categorized and grouped by the number of days before or after Nonpareil hullsplit as follows:

  • Kapareil group: 10 days before Nonpareil
  • Sonora group: 7–13 days after Nonpareil
  • Price group: 15–21 days after Nonpareil
  • Butte group: 23–28 days after Nonpareil
  • Carmel group: 29–34 days after Nonpareil
  • Mission group: 39–40 days after Nonpareil
  • Fritz group: 40–54 days after Nonpareil

In commenting about harvest, Duncan noted some varieties, like Fritz and Monterey, harvest late, potentially exposing the crop to rain damage and possibly precluding the planting of these varieties in some areas. In addition, some varieties like Sonora and Price may harvest too soon after Nonpareil, so that it may be difficult to put on a post-harvest irrigation for Nonpareil, especially in flood or solid-set-sprinkler-irrigated orchards, until after the pollinizers are also harvested.

For information on almond varieties, including the complete conference panel presentations and reports from the Regional Variety Trials (RVT) sponsored over the years by the Almond Board, go to AlmondBoard.com/farmpress21. In addition to the presentations, reports from the RVT are worth studying; they contain detailed performance data on the items covered in this series. Another valuable resource is the chapter, “Evaluation and Selection of Current Varieties,” in the Almond Production Manual, Publication 3364, UC Division of Agriculture and Natural Resources, published in 1996. Future articles in this series will look at insect and disease susceptibility, kernel quality, “fit” into the farming operation, and the “risk/reward” of trying newer varieties.