This article is the second in a series  on choosing almond varieties.
This second article looks at the “checklist” of issues to consider when choosing almond varieties in terms of bloom, pollination and harvest timing. At the 2009 Almond Industry Conference, a panel of experts gave growers assistance in this choice by reviewing variety development, evaluation and selection, balancing both field and market considerations. The panel included Tom Gradziel (UC Davis almond breeder), Joe Connell (UC farm advisor, Butte County), Bruce Lampinen (UC Pomology Extension specialist), Ned Ryan (past Almond Board chair and almond industry consultant) and Roger Duncan (UC Davis farm advisor, Stanislaus County).
Almond varieties are grouped by approximate peak bloom periods, based on days before or after peak Nonpareil bloom. They are classified as:
- Early: six days or earlier before Nonpareil peak
- Early-mid: five days to one day before Nonpareil peak
- Mid-late: coincides with two days after Nonpareil peak
- Late-mid: three to four days after Nonpareil peak
- Late: five to seven days after Nonpareil peak
- Very late: eight days or more after Nonpareil peak
An updated listing of varieties in each bloom group is included in farm advisor Joe Connell’s presentation (see link to all presentations in last paragraph).
As a rule, the better the variety bloom overlap, the better opportunity for cross pollination. It is best to choose varieties in the same group or adjacent groups, said farm advisor Roger Duncan in his presentation. Good bloom options for Nonpareil also include those in the mid groups: Aldrich, Price, Fritz, Solano, Carmel and Wood Colony. Other options are those that have a peak bloom just before or after Nonpareil peak. These include Winters and Peerless in the early-mid group (just before Nonpareil peak), and Monterey in the mid-late group (just after Nonpareil peak).
Duncan added that to maximize yield potential, it is best to have two pollinizer varieties in addition to the main variety, such as Nonpareil, for a total of three. This is based on results of separate field tests he and Connell are conducting. Smaller operations that rely on custom harvest may want to consider just two varieties — the main variety and a pollinizer. For this scenario, Duncan advised, good matches for Nonpareil include Winters, Aldrich, Price, Carmel, Wood Colony and Fritz. Another option for smaller growers without harvest equipment is to grow varieties that can be harvested at the same time but not necessarily mixed. These include plantings with Aldrich, Winters, and Carmel or a Butte/Padre combination.
Another bloom consideration is the order of bloom time between varieties. A variety that blooms early will inherently have a higher set than a later bloom variety. For instance, if Nonpareil is the main variety, then a variety that blooms just ahead of or at the same time as the Nonpareil peak is much better than a variety that blooms later.
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.
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.