UPDATE - BLUEBERRY PRODUCTION IN MILD COASTAL GROWING AREAS
 The potential for fresh blueberry production in mild California growing areas has been discussed in several articles in previous issues of Central Coast Agricultural Highlights (March 1996, February 2000, October 2000, May 2001). New commercial blueberry plantings have been established over the past three years from northern San Luis Obispo County south to San Diego. The majority of blueberry plantings in California are targeting early market windows from March to June when high prices prevail. Field trials are also evaluating the potential for late summer/fall harvest by manipulating cultural practices. Experience to date indicates that although there are a number of factors important to successful blueberry production in California, two are especially critical:
- Cultivar selection
- Soil pH management
Cultivar Selection
For early season production, it is critically important to select a cultivar to match the typically low amount of chilling temperature accumulated in mild growing areas. The Southern Highbush (SHB) types of blueberries best combine low chilling requirements with fruit yield and quality. Ideally, the cultivar should also be early maturing. With early maturing fruit cultivars, generally, there is greater frost risk in the spring, and even mild areas typically receive some frost. Blueberry plantings directed at early season production will likely require overhead sprinkler irrigation for frost protection, even if the primary irrigation system uses microsprinklers or drip.
Many of the new planting sites have multiple blueberry cultivars planted, and additional information is also available from established field trials.
The SHB cultivars currently available, which best combine earliness and very low chill, are the following:
- Sharp Blue
- Misty
- Wannabe (Florida Blue)
- Jewell
- Biloxi
- Saphire
Of these cultivars, yield data is only available, thus far, for Sharp Blue, Misty and Wannabe. These and other SHB cultivars are currently in trials at multiple coastal California trials. Jewell, Saphire, and Biloxi are relatively newly released cultivars that are currently in experimental trials but have not yet reached harvest maturity. Jewell, Saphire and Biloxi all show excellent overall vigor in trials thus far, and appear promising as additional early, low chill SHB cultivars.
Three years of growth are needed for the first harvest, and it is not unusual for blueberries to last 30 years, so very little data is yet available comparing a broader range of cultivars in different environments in California. A previous article (May 2001) summarized production periods and yields in California from those cultivars for which data is available.
There are additional SHB cultivars that, while one to four weeks later in maturity than the above group, also have sufficiently low chill requirement for mild, coastal plantings. These cultivars, Marimba, Gulf Coast, Georgia Gem, and Cape Fear also appear to be productive and generally well adapted. The cultivar Georgia Gem was not one of the more productive cultivars in early harvest seasons (year 1-2), but yield and vigor appear to be improving. The cultivars Emerald, Millenia, Windsor, Star, and Cape Fear are SHB cultivars that also may have promise as additional potential cultivars, depending on the specific site. These and other additional SHB cultivars are under evaluation at multiple locations.
Soil pH Management
Blueberries grow best at a soil pH below 5. Most soils at coastal California growing areas range 6 to 7.8. All of these soils will require a considerable amount of incorporated sulfur (S) prior to planting, and additional annual, topdressed sulfur application. It is important to determine the per acre sulfur requirement prior to planting by testing soil pH and using applicable tables or a lab analysis to determine S requirement.
The most effective commercial S materials for rapid pH adjustment are sulfuric acid, Tiger sulfur, and Dispersul. Sulfuric acid requires special equipment for safe application and should only be attempted by experienced personnel. It is important to try to uniformly incorporate the S materials when preparing the beds for planting. Wood waste should be incorporated into the bed if the soil is poorly drained. Blueberries have relatively shallow root systems and do not tolerate poor drainage or drought.
It is common that pH will be quite variable within newly established blueberry beds following S incorporation. The desired lower pH may not be completely uniform in the bed for several months. It is important that soil volume close to the plant has a pH below 5, and additional localized S application may be needed. Thiolux is another S material that is water soluble and commonly used for mildew control, but which also has a nutrient label. A Thiolux drench may be applied to assure adequate acidification of the soil volume close to the plant.
The management of soil pH is especially critical in years one and two, and growers should pay close attention to timely and uniform sulfur applications, and the pH environment surrounding the roots of the young plants. If the young blueberry plant is planted into a root zone pH above 5, the plant will show low vigor and pale green-yellow (chlorotic) new growth due to iron deficiency. The plant is slow to initiate new growth, and the growth is weak. The plant develops very slowly or not at all. If growing conditions are otherwise adequate, a young blueberry plant should begin to initiate new growth 50-70 days after planting, and the foliage overall should have a uniform green to blue-green color down the entire row.
Other cultural practices can also be important in successful blueberry management, depending upon circumstances. Cultural practices such as land preparation, mulching, water and fertility management, pruning, and bird control have been summarized in prior articles in Central Coast Ag. Highlights. For more information contact this office at 805/934-6240.
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