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News from the Edible Demo Garden

March 2022: Growing Blueberries

Choose low chill hour varieties for Marin. Brenda Dawson
Choose low chill hour varieties for Marin. Brenda Dawson
Blueberries are the focus of the newest demo garden project. Blueberries grow on long-lived and attractive shrubs and are both delicious and nutritious. They can be an ideal addition to an edible garden or to a home landscape if their growing conditions are met. Whether these conditions could be met in the edible demo garden is the question driving the project. While strawberries and raspberries have grown successfully in the demo garden, blueberries can struggle in hot dry summers.


Growing Conditions for Blueberries

Blueberries are in the Ericaceae family and are related to rhododendrons and azaleas and thrive under similar conditions. They need:

  • Full sun with some shade protection in hot weather
  • Acid soil (pH 4.5 to 5.5)
  • Ample water
  • Good drainage

Much of our Marin garden soil is not sufficiently acidic for blueberries so it’s necessary to create it using pH lowering organic amendments such as peat moss or elemental sulfur. A layer of organic mulch will help keep the soil cool and moist and will protect the shallow roots. Regular feeding with acid-forming complete fertilizers will provide nutrients and help maintain the low pH.


Selecting the Best Varieties

Blueberries native to the northeastern US require too many annual chill hours (hours with temperatures between 32 to 45 degrees), to grow well in Marin. Fortunately, there are many cultivars with low chilling requirements available. Ripening time is another consideration. There are early season, midseason, and late season varieties. Planting at least two different varieties improves pollination and increases production, so choosing kinds that ripen at different times increases harvest length. Two hybrid “varieties were chosen for the edible demo garden:

  • ‘Misty’. Classified as southern highbush variety, it produces very early, large, good-flavored fruit. It has a 150 to 300 chill hour requirement and tolerates a higher than usual soil pH.
  • ‘Blueray’. It is a southern highbush midseason variety with a chill requirement around 500 hours. It produces large, flavorful berries and is more tolerant of summer heat than some other varieties.


Promoting Production

The best fruit production requires patience and careful pruning. Removing blossoms the first year or two allows the plant to focus its energy on vigorous growth. Initially pruning all branches back to about 30% also promotes new growth. In following years, older branches or weak shoots can be removed, but fruit is produced on 1-year old wood so excessive pruning will reduce yield.

For more information, see our grow sheets on blueberries! 

If the edible demo garden blueberry project is a success, the next problem will be keeping the birds from devouring the crop.