Blueberries

By Tami Reece, UC Master Gardener 

  Blueberry Varieties

• Considerations in choosing blueberry plants: taste and fruit size, harvest dates, climate, plant form and foliage. Some varieties are deciduous, losing their leaves in the winter.
• Most blueberries are self-pollinating, but for larger berries and consistent yields, plant at least two different varieties.
• Northern highbush, rabbiteye, and southern highbush are the most common types of blueberries grown in the U.S.
• Southern highbush is the variety best suited for SLO County as it has lower chill requirements, some drought tolerance and will tolerate summer heat.
• Chill hours: blueberries, like other fruits, have a chill hour requirement. Winter hours below 45 degrees are required to break dormancy and bloom. North county typically has 800-1000 chill hours, SLO and south county have 250-450 chill hours. If you live in south county and have a high chill blueberry, the result could be little or no fruit.
• Southern highbush blueberry varieties for SLO county include: O’Neal, Sharpblue, Sunshine Blue, Misty, Southmoon, Revielle, Gulf Coast, Georgia Gem, Marimba.
• Northern highbush varieties for north county: Earliblue and Bluecrop.

Site Selection & Preparation

• Sunny location, at least 6 hours; afternoon sun in hot climates; easy access to irrigation water.
• Soil preparation is crucial for success; blueberries require well-draining, acidic soil (pH 4.5-5.5) with high organic material. Test soil using soil pH test kit available at garden centers.
• To lower pH, add soil (elemental) sulfur available at garden centers and follow package directions. Test soil annually and add soil sulfur as needed.
• To improve soil aeration and drainage: add organic matter such as composted pine bark, fir bark, oak leaves, or pre-moistened peat moss. Peat moss also helps lower soil pH. Planting in raised beds can aid in soil management and drainage.
• Blueberries are excellent container plants. Select a compact bush variety such as Sunshine blue or Top Hat. Use potting soil designed for acid loving plants or the Dave Wilson Nursery’s recommended blueberry mix of 1/3 ¼” landscape bark, 1/3 peat moss, 1/3 acid plant soil and 1 handful of soil sulfur per container.
• Dig a hole 3 or 4 feet wide by 2 feet deep. Plant the blueberry at or slightly above ground level.
• Plant 2 ½ feet apart to form solid hedgerows or 4-6 feet apart for individual bushes and ample harvests. Plant rows 6 feet apart.
• After planting, irrigate and cover the soil with 4-6 inches of mulch, preferably fir, pine bark chips, or pine needles.

Irrigation & Fertilizing

• Blueberries are sensitive to over-fertilizing. Observe if the plants are growing and fruiting well. If needed, use fertilizer for acid loving plants and apply according to manufacturer's directions. Organic fertilizers such as blood meal, cottonseed meal, fish meal, and alfalfa meal may also be applied.
• Blueberries require moist but not continually wet soil. Regular irrigation provided by drip irrigation or a soaker hose is critical during berry development. Use a soil moisture meter to assure moisture to depth of 2 inches.
• Blueberries have shallow roots and should not be allowed to dry out. They need regular irrigation from bloom to harvest. Mulch can help retain moisture.

Pruning

• Blueberries should be established before allowing to bear fruit. Remove all blooms at planting and as they appear the first year.
• Years 2-3, remove dead, diseased or damaged branches and spindly growth at base of plant. Thereafter, blueberries need annual winter pruning to remove damaged or weak and spindly growth to maintain healthy strong wood.

Pests

• Birds: most significant pest; use bird netting for consistent control.
• The spotted wing drosophila is a tiny fly that lays eggs in ripening fruit, especially in coastal regions. The small white larvae feed on the fruit. Minimize infestations by removing any fallen or infected fruit and by harvesting fruit as they ripen. The use of plastic mulch under the plants has been shown to reduce infestation of fruit. Spinosad can be used to control at the pink fruit stage and prior to harvest.
• Citrus thrips: avoid planting blueberries near citrus. Thrips are usually not a problem in coastal areas but may appear in spring and summer. They can cause stunting of new shoots, coupled and curling of new leaves, but does not damage fruit so no treatment is recommended.

References:

Blueberry Varieties. UC Master Gardeners Santa Clara County. Blueberry Varieties - UC Master Gardeners of Santa Clara County

Garrison, Nancy. Blueberries: 1997 Santa Clara County Trials. 2003. UC Master Gardeners Santa Clara County. Blueberries: 1997 Santa Clara County Trials - UC Master Gardeners of Santa Clara County

Ingels, Chuck. Growing Blueberries in the Sacramento Region.  Environmental Horticulture Notes EHN 88.  UCCE. 138069.pdf

McIntosh, Hanna, Michael Bartlett Smith et al. Modifications of plant microclimate by plastic mulches reduces Drosophila suzukii infestation. Journal of Pest Science. 12 Jan 2024. https://link.springer.com/article/10.1007/s10340-023-01715-4