California Farmer – June, 2003
Searching for a perfect method of pollination breeds seeds of discontent.
By Joe Traynor
Selecting mandarin varieties for a new planting increases your awareness that there is no perfect variety – all have one or more flaws. These notable negative traits include poor fruit set, reduced fruit size and excessive fruit drop – all caused by inadequate pollination. Negative traits can be neutralized by providing adequate pollination or by planting different varieties for cross pollination.
For consistent high yields, mandarin growers focus on selecting varieties with good fruit characteristics and making sure they provide ample pollination. But this is often easier said than done.
The Clementine family of mandarins has proven especially popular in recent years because of their intense flavor and their zipper skin. The first planting of Clementines in the San Joaquin Valley (SJV) included two or more varieties in one block to insure adequate pollination. These blocks produced high yields of quality fruit with one fatal flaw: excessive numbers of seeds.
Seediness in mandarins was not a major factor 20 years ago when consumers accepted seedy citrus in the same way they accepted grapes and watermelons with seeds. Today, however, seedless red grapes have taken the market from the otherwise great-tasting seeded varieties, and growers are grafting over or replanting to seedless varieties. Seedless watermelons now dominate that market as well.
Today’s fast food consumer, especially in the United States, simply doesn’t have the time to be bothered with spitting out seeds and will select food products that eliminate the practice and time burden. Seedless fruit is considered a value-added product and has become part of the quality demanded in the produce industry as a global marketing strategy.
Indeed, nurseries should add a warning label when marketing Clementine mandarin trees: Caution: plant these trees in solid-block planting only or you may not be able to market your fruit.
There are multivariety Clementine plantings in the SJV that produce seedy fruit that is difficult to sell in competition with seedless product from New Zealand or Spain. There are also solid-block, one-variety plantings that produce seeded fruit because there are other pollen producing citrus trees (including Valencias) close by. University of California (UC) researchers recommend that one-variety planting of Clementines be insulated on all four sides with buffer rows of pollen-sterile citrus like Navels.
WHAT’S THE ANSWER?
The ultimate answer to this pesky problem is to plant varieties with sterile ovules that will produce seedless fruit even when bees are present. These varieties include Pixie, Gold Nugget and three new UC varieties, Shasta Gold, Tahoe Gold and Yosemite Gold. Unfortunately, these varieties don’t have all the favorable characteristics of the popular Clementine varieties. These characteristics include early ripening, to catch the early market and to minimize frost danger.
Even so, seedless mandarin varieties still require some stimulus to ensure maximum fruit set and size. Judiciously timed sprays of Gibberelin or 2,4-D show some promise in this regard. Honeybees can provide the same beneficial stimulus (growers of seedless watermelons rent bee colonies for this purpose).
-Joe Traynor is a consultant-writer and author of “Honey – The Gourmet Medicine,” published last year.
Bee ban option
If only bees could read “no trespassing” signs, they might be kept out of multivariety Clementine plantings and the amount of seedy fruit would be minimal. In Spain, some Clementine growers use insecticides to keep their groves free of bees, but it is doubtful that such a solution would be allowed in California.
California Clementine growers believe they can keep honeybees out of their groves by convincing (or paying) their neighbors not to allow beekeepers to place bees within a mile of an orchard. However, these growers are in for a rude awakening at bloom time when they discover abundant bee activity on their mandarins. Citrus blooms are prolific nectar producers, and honeybees will travel up to four miles to work citrus bloom.
Some beekeepers are already persona non grata on citrus locations they have worked for years. Although the landowner might not have mandarins (or any citrus) he tells the beekeeper, “I have to get along with my neighbor.” Transient beekeepers have little clout in such a situation. Some beekeepers are getting around the problem by purchasing small parcels of land within a large citrus area.
Pushing beekeepers off long-held locations would have a devastating effect on California beekeepers, since citrus honey production is the back-bone of California’s bee industry. In a dry year, such as 2002, citrus honey is the only honey that many beekeepers will make. The only other source of income for many state beekeepers is income from almond pollination fees, and almond growers are already paying more than their fair share to keep beekeepers in business.
– By Joe Traynor