Growing Blueberries: Vaccinium

Botanical Overview

A member of the Heath family (Ericaceae) which includes Azaleas, the genus Vaccinium (Blueberry) comprises 37 species plus hybrids. A few of these are used in commercial fruit production.
Two types of blueberry are appropriate for fruit production in warm climates: Southern Highbush Blueberry, a collective name for Highbush Blueberry hybrids with various southern blueberry species; and Rabbiteye Blueberry.
Southern Highbush blueberries are larger, have thinner skin, are juicier, and ripen about a month sooner than Rabbiteye.
Rabbiteye blueberries are sweeter but have thicker skin which gets tougher after freezing. Rabbiteye shrubs are more drought tolerant, more tolerant of higher pH ranges (5.5-6.5), and less prone to disease than Southern Highbush shrubs. But Rabbiteye grows to be a monster 20' (6m) high shrub unless hedge trimmed or grown in a container.
"Wild" blueberries are produced by the Lowbush Blueberry, which grows in northeastern North America from Canada to Virginia.

Description

Form: A shrub composed of canes growing from a root crown.

Lifespan: 20-50 years.

Leaf retention: Semi-evergreen or deciduous, based on the length of time before dropped leaves are regrown.

Growth rate: Moderate.

Mature Size: 4-6' (1.2-1.8m) high and as wide is typical for a container plant.

Flowers: White to pink, small, waxy, hanging lantern shaped, clustered.

Bloom: Late winter or spring.

Self-fruitful: Usually. A different cultivar is needed for cross pollination to produce a higher yield even when a plant is self-fruitful.

Years before fruiting: None, but all flower buds should be removed the first year so that the plant can spend its energy developing roots instead of fruit.

Fruit: Spherical shape, dark blue skin, edible. Tiny seeds.

Months for fruit to ripen: 2.

Storage after harvest: Place in a sealed glass or plastic container without washing and refrigerate for up to 2 weeks. Washing causes blueberries to last no more than 5 days in a refrigerator even when dried on a paper towel. Frozen blueberries will last up to one year.

Leaves: Green, smooth edges, oval with pointed tip to broadly lance shaped.

Stems: No thorns. New canes (main branches) grow from the root crown.

Roots: Shallow, mostly within the top 7" (18cm) of soil, weak.

Cultivars of Note for regions with hot summers:

'Jewel' 200 chill hours, high yield commercial variety, self-fruitful

'Misty' 150 chill hours, especially adapted to heat, self-fruitful

'Sharpblue' 200 chill hours, long bearing season, self-fruitful

'Southmoon' 200-300 chill hours, taste test winner, self-fruitful

'Sunshine Blue' 150 chill hours, semi-dwarf, self-fruitful

Wildlife: The flowers attract bees, the fruit attracts birds. Plants must often be netted to avoid bird predation.

Toxic / Danger: No.

Origin: North America. Most commercially grown food crop species originated on the east coast.

Cultivation and Uses

USDA hardiness zones: 7-10 for most low chill cultivars.

Chill hours: Choose cultivars needing 300 chill hours or less in USDA zones 9-10.

Heat tolerant: Yes.

Drought tolerant: No.

Sun: Full sun in the morning, afternoon shade in USDA zones 9-10.

Planting: Plant blueberries in January, when they are dormant, in a 20-24" diameter (70-110 liter) container. Locate the containers where they will get appropriate sun exposure and good air circulation. The containers must have sufficient holes at the bottom of their sides to drain water adequately.

Soil: Well draining, high in organic content, pH 4.0-5.5 (very strongly acidic). Blueberries must be grown in large containers to maintain soil acidity in regions with alkaline soils. If plants show a nutrient deficiency, it is usually because the pH is too high. For residential gardening, the soil can be composed of 1/3 peat moss, 1/3 untreated bark 1/4-1/2" (0.6-1.2cm) size (pine is good, avoid cedar and redwood), 1/3 azalea or acid-plant potting soil, and 2/3 cup soil sulfur per plant.

Fertilize: Use slow release fertilizers, without nitrates, formulated for acid-loving plants. Nitrates will inhibit or harm the plant. Azalea and rhododendron fertilizers work well.

Water after becoming established: Daily. Never let the soil dry out entirely. A drip emitter system is ideal for watering blueberries. Make sure all containers drain well.
Blueberries are "calcifuges", very sensitive to calcium and sodium salts in the water, salts typically found in desert water sources. Collected rainwater is best.

Mulch: Spread organic over the root zone and 1' (30cm) away from the root crown to reduce heat stress and evaporation loss.

First Year Care: Do not fertilize during or after planting until new growth has started. Remove all flower buds the first year so that the plant can spend its energy developing roots instead of fruit.

Prune: In early winter, remove all dead wood and low-growing branches which are more prone to disease. Berries grow on one year and older wood.
Cut off short shoots that have fewer leaf and flower buds to open the plant out. If done properly, 50-75% of flower buds will be removed so that the plant will have fewer fruit and can grow them to a larger size.
The oldest canes (vertical branches growing from the root crown) are the largest in diameter and produce less fruit after six years. After six years, start removing the oldest (largest diameter) canes but not more than one-sixth of all canes. Cut them at ground level just above the root crown. On average, only one or two canes will be removed, all six years old.

Litter: Moderate. Keep the area around the plant free of fallen leaves, branches and fruit to prevent fungal diseases.

Propagation: Cuttings.

Uses: Edible fruit, ornamental, bird garden.

Comments

When growing blueberries, buying two different cultivars is recommended because diverse cross-pollination greatly increases fruit set. Growing blueberries in containers to ensure properly acidic soil is mandatory in regions with high soil alkalinity.

Do you have additional information or a different experience for these plants that you would like to share? Email info@GardenOracle.com. All contributions are welcome and appreciated.