Growing Blueberries in Santa Clara County

Video: Growing and Pruning Blueberries (100 minutes, on vimeo.com)

Introduction

In February 1997, a group of Master Gardener volunteers established a variety trial to evaluate 15 varieties of blueberries in a replicated trial. This was conducted at the Bay Area Research and Extension Center of the University of California located in the City of Santa Clara near Valley Fair Shopping Center. The objective was to determine which varieties of blueberries grow and produce best under our soil and climatic conditions in Santa Clara County. The South Bay Area has not been known as a blueberry growing area, but a few people, including myself, have been growing them successfully for nearly a decade.

We trialed Northern Highbush (Vaccinium corymbosum), Southern Highbush (Vaccinium darrowi), as well as interspecific hybrids. Each of the 15 varieties were replicated four times with four plants per replication totaling 255 blueberry plants. There was also a border row on the east and west perimeters which contained one or more of each of the varieties. Fall Creek Nursery in Oregon was the source for all plants included in this trial.

Varieties

Blueberry varieties are distinguished by their climate suitability and ripening season. One might want to select varieties that ripen at different times or feature large fruit (best for fresh eating and desserts) or small fruit (best for muffins and pancakes). Bushes with brilliant fall color or different growth habits offer the gardener lots of choices to use throughout the landscape. Plant at least two plants per family member.

Site Selection and Preparation

Select a sunny location where irrigation water is available as best results will be obtained by keeping the root zone moist throughout the growing season. Where the soil is poor or marginally drained, amended soil in raised beds work well.

A fail safe way to grow blueberries in almost any soil is to incorporate peat moss into the planting medium. A more sustainable product, but one that will more quickly decompose, is oak leaf mold, which is decomposed oak leaves. For planting directly into the ground, work up a planting area approximately 2.5 feet in the diameter and one foot deep. Remove one third to one half of the soil. Add an equal amount of premoistened peat moss, two cups soil sulfur, 2 tablespoons of phosphate fertilizer and mix well. One 4-cubic foot compressed bale will usually be sufficient for 4 to 5 plants. For raised beds, mix equal volumes peat moss with acid compost or planting mix. Blueberries thrive in acidic soils that have a pH of 5 – 6. The pH of soils in much of Santa Clara County are between 7.0 – 7.6.

Strangely enough, established blueberry plants in San Jose that are 14 years old as of 2003 have done beautifully with no ongoing acidic fertilization since the year they were planted; just mulched.

Spacing

Blueberries can be planted as close as 2-1/2 feet apart to form solid hedgerows or spaced up to 6 feet apart and grown as individual specimens. If planted in rows, with one row after another, allow at least 6 feet between rows.

Planting

For container stock, remove from pot and lightly roughen up the outside surface of the rootball. Set the top soil line of the plant about 1-2 inches higher than the existing ground and firm around rootball. Mound soil up along sides of exposed root mass. Firm soil around roots and water well.

Mulching

Blueberries do best with a 2 to 4" of mulch over the roots to conserve moisture, prevent weeds and add organic matter. Bark mulch, pine needles, acid compost, sawdust, grass clippings, etc. all work well.

Pruning

It is important that blueberries get established before allowing them to bear fruit. Thereafter, they should be heavily pruned each year to avoid overfruiting which results in small fruit or poor growth.

  • Remove all blooms as they appear the first year. Remove low growth around the base. If it doesn't grow up, it gets pruned out!
  • Remove the dead wood, and non-vigorous twiggy wood. Select for bright colored wood with long (at least 3 inch) laterals. Remove blotchy colored short growth.
  • If one third to one half of the wood has not been removed by the above steps, thin out the fruiting laterals and small branches until this balance has been obtained.

Fertilizing

Blueberries like acid fertilizers such as Rhododendron/Azalea/Camellia formulations. For newly planted stock, use 2 tablespoons of 10-20-10 (or similar fertilizer) in late spring or once plants are established. (Careful! Blueberries are very sensitive to over nitrogen fertilization!) For subsequent years, use 3 tablespoons of fertilizer for each year from planting to a total of 5 tablespoons per plant. Apply in early spring and again in late spring for best results. Always water well after fertilizing. For organic fertilizers, blood meal, alfalfa meal and cottonseed meal work well by sprinkling on soil surface and re-covering with mulch. The worms will work the material into the root zone in time. Avoid using fresh manures

Conclusions

To date, favorite varieties are Reveille, Misty, and Bluecrop because they have excellent flavor defined as a "wild" blueberry flavor, intense with a good sugar/acid balance. They are also very productive.

Article by Nancy Garrison
Revised: 01-Mar-2003