Establishment and Management of the Cultivated Lowbush Blueberry (Vaccinium angustifolium)

Abstract

Cultivated blueberries (Vaccinium corymbosum and V. virgatum) have been propagated and planted successfully throughout the world. The lowbush blueberry (V. angustifolium and V. myrtilloides) have large areas of production in the state of Maine in the United States and in the Atlantic and Quebec Provinces in Canada on managed naturally occurring native stands. Except for some small demonstration plantings in Canada and a few plantings in Northern China, it has not been managed as a cultivated plant. Extensive plantings of cultivated lowbush blueberries have not been developed because of the slow establishment and lack of rhizome production from cuttings that limit its productivity compared to the cultivated blueberry. Tissue culture plants offer a more juvenile growth habit and quicker establishment, but may not yield as well as cuttings. Lowbush blueberry plants establish from seed quicker but have more genetic variability and a lower yield. A seed propagated lowbush blueberry family such as ‘Novablue’ will provide both rapid establishment and high yields. If planted on the proper sites and managed in the same manner as the wild blueberry, this would provide cultivated lowbush blueberry fields that are more productive than their native North American wild blueberry counterparts.

Keywords:

• wild blueberry
• propagation
• establishment
• seed propagated lowbush blueberry families

INTRODUCTION

The lowbush blueberry (Vaccinium angustifolium and V. myrtilloides) is also referred to as the wild blueberry where it is grown commercially in the state of Maine in the U.S. and in Canada in the Maritime and Quebec provinces (Yarborough, 2009; Strik and Yarborough, 2005). The wild blueberry is a low-growing rhizomatous shrub that is managed from naturally occurring native populations of plants. It is characterized by large amounts of genetic diversity and wide variability in yield (Hepler and Yarborough, 1991; Yarborough, 2009). Recent improvements in management practices have resulted in a four-fold increase in productivity over the last 20 years (Yarborough, 2004). The lowbush blueberry is intermediate in size between the larger highbush blueberry (V. corymbosum) or rabbiteye blueberry (V. virgatum) and the European bilberry (V. myrtillus) or bog blueberry (V. uliginosum) (Fig. 1).

FIGURE 1 Comparison of size of lowbush, highbush, and bilberry fruit. (Photo complements of Sonia Dierking, www.dierking.de.) (color figure available online).

There has been growing interest in establishing plantings of the lowbush blueberry because of its ability to grow in a Northern climate and because its oxygen radical absorbance capacity (ORAC) value is twice that of the cultivated blueberry (Kalt et al., 2001). The ORAC values of bilberries or the wild lingonberry (V. vitis-idea minor) (Leiner et al., 2006) are even higher. Although domestication of the lowbush blueberry through selection and breeding has been advocated for many years (Hall, 1983; Kender, 1967) and demonstrated on small plantings in North America, extensive plantings have not taken place because of the slow establishment and lack of rhizome production from cuttings (Jamieson and Nickerson, 2003). An economic study in 1990 (Blatt and O'Regan, 1990) revealed that because of the higher yields of the cultivated lowbush blueberries, the economic return could be higher than that of native stands. Although improvements in plant spread may be obtained by using tissue culture plants, this does not always result in higher yields (Jamieson and Nickerson, 2003; Litten and Smagula, 2000). The largest cultivated planting of cultivated lowbush blueberry is now in Jilin and Liaoning provinces in China (Li and Yu, 2009).

The objective of this article is to discuss the best plant materials and management practices for establishing and managing cultivated lowbush blueberry plantings.

MATERIALS AND METHODS

Field Establishment

Location

Wild blueberries are commercially grown on cleared, unplowed forest soils or on abandoned agricultural lands (Smagula and Yarborough, 2006); but they can tolerate a wide range of climatic conditions in a temperate climate (Hall et al., 1997). The plants grow best in a well drained acidic soil (pH 4.0–5.0) with sufficient organic matter (5–10%). Previous blueberry plantings in China have shown the lowbush plants to be the most poorly adapted to summer flooding (Wu et al., 2002). Other limiting factors there included cold dry winter temperatures below –30°C without snow cover causing winter kill and spring frosts that can damage flowers. The southern limit of lowbush blueberry culture is restricted by chilling hours; approximately 1,000 hr below 0°C are required for plants to break dormancy.

Plant source

Lowbush blueberry cultivar releases are very limited compared to highbush varieties. Only six cultivated lowbush varieties, i.e., ‘Augusta’, ‘Brunswick’, ‘Chignecto’, ‘Blomidon’, ‘Cumberland’, and ‘Fundy’, have been released from the Atlantic Food and Horticulture Research Centre, Kentville, Nova Scotia, Canada (Anonymous, 1997b). Early plantings with stem cuttings were not successful due to inconsistent rhizome production resulting in slow establishment (Jamieson and Nickerson, 2003). Because lowbush blueberries grow to less than 0.5 m in height, it is important to have as much of the ground covered with new stems from the rhizomes in order to produce greater quantities of fruit. Tissue culture propagated plants provide a more seedling-like growth habit and will spread more rapidly (Litten and Smagula, 2000), but did not yield as high as plants from cuttings (Jamieson and Nickerson, 2003). Plants grown from open pollinated seed of superior clones had higher variability and lower yields than the cuttings or tissue culture plants, but had the advantage of producing more rhizomes and establishing more rapidly. When seeds were obtained from crosses between high yielding varieties, then both rapid establishment and high yields were obtained (Jamieson, 2008a). ‘Novablue’ is a seed-propagated lowbush blueberry family released by the Atlantic Food and Horticulture Research Centre, Kentville, Nova Scotia, Canada (Jamieson, 2008b) and has the advantage of lower cost of plant material with more rapid plant spread while still maintaining some of the genetic diversity that gives the wild blueberry its characteristically unique flavor.

Planting and density

Because the lowbush blueberry is a perennial and native plantings have been in production for over 100 years, the land should prepared by tilling, have a high organic matter, and be free of weeds prior to planting. Land should be tilled a year in advance and perennial weeds controlled. A green manure crop may also be established and plowed under prior to planting. Plants should be grown for least 2 years before planting into the field. Blueberry plants should be planted as early in the spring as conditions will permit. Plants should be spaced at 45 cm in the row with rows 90 cm to 120 cm apart; this would require 20,000 to 25,000 plants per hectare. Blueberries should be planted so that 5 to 7 cm of the shoot growth will be below the soil surface so that it reduces frost heaving and encourages early rhizome development (Fig. 2) (Anonymous, 1997a). Two or more cultivars are needed to assure adequate fruit set if cuttings or tissue culture plants are used, but ‘Novablue’ does not require other pollinizors (Jamieson, 2008b).

FIGURE 2 Planting depths for cultivated lowbush blueberry.

Mulching

Mulching lowbush blueberry plants at an establishment provides many benefits, including: preventing frost heaving; suppressing weed growth; moderating soil temperatures; reducing water loss; reducing soil erosion; and stimulating rhizome growth (Chiasson and Argall, 1995). Bark mulch has produced the best rhizome spread followed by sawdust, peat, and wood chips (DeGomez and Smagula, 1990). Mulching will allow the lowbush blueberry to fill in the entire field to produce the most yields for the land area used. There is no need for rows in a cultivated lowbush blueberry planting.

RESULTS AND DISCUSSION

Field Management

Pruning

To encourage maximum rhizome growth, the new lowbush planting should be allowed to grow without pruning for 4 years (Chiasson and Argall, 1995). Then it should be treated according to standard practices, where the plants are pruned to the ground in late fall or early spring every other year. This practice has been shown to produce the maximum productivity (Yarborough and Hess, 1998). It results in a crop only in alternate years, but also provides for pest management by interrupting disease and insect cycles (Yarborough, 2006).

Weed control

Weeds have been a major limiting factor to wild blueberry growth and production and the use of selective herbicides has allowed for increased fertilizer, pollination, and irrigation to increase the wild blueberry crop by four-fold (Yarborough, 2004). Although the use of mulch will help suppress weeds, the addition of sulfur to reduce the pH to 4.0 has also been demonstrated to suppress weeds without herbicide applications (Smagula et al., 2009, Yarborough and Guiseppe, 2006). Current recommendations for wild blueberry weeds and their control options may be obtained at the web site: http://nsac.ca/wildblue/facts/weeds.asp.

Fertilizer

No correlation has been found between soil nutrient levels and plant productivity, so except for the use of soil pH to reduce weed competition, soil samples are not used to determine fertilizer needs. Leaf samples taken at the tip dieback stage for N and P have indicated that the addition of diammonium phosphate fertilizer can increase yields if the leaf N is below 1.6% and the leaf P below 0.13% (Smagula and Yarborough, 1999; Yarborough and Smagula, 1993). In addition, the application of gypsum has been found to increase nutrient uptake and improve crop growth (Sanderson and Eaton, 2004).

Pollination

Blueberry flowers must be insect pollinated, and the more visits the greater the number of seeds, which translates into fruit size increases and higher yields (Yarborough, 2006). Native bees, bumblebees, and honeybees all pollinate the wild blueberry and it has been shown that additional pollination is necessary to produce the highest yields on native stands and requires 2.5 hives/ha to produce 1,000 kg/ha (Yarborough, 2004).

Irrigation

Wild blueberries require 2.5 cm of rainfall per week or supplemental irrigation in the growing season for the best production (Hunt et al., 2009). Excessive moisture that floods the fields reduces yields, and if flooding exceeds 32 days this could result in plants not recovering (Wu et al., 2002). Overhead irrigation is less efficient than drip but can provide protection from frost if needed and is easier to remove than drip irrigation when pruning the plants (Yarborough, 1999).

Pest management

There are a few diseases, including Mummyberry (Monilinia vaccinii-corymbosi), and a number of insects, such as the fruit fly (Rhagoletis mendax), that cause reduction in yield and quality of the lowbush blueberry. A more comprehensive source of pests and control measures may be found at the web site: http://nsac.ca/wildblue/facts/. The advantage of introducing lowbush blueberries into areas where they have not previously grown is that these pests are usually not a problem; but native pests, such as the Queensland fruit fly (Bactrocera tryoni), can adapt to blueberries as it did in Australia (Ireland and Wilk, 2006).

Harvesting

Unlike cultivated blueberries that are hand harvested for the fresh market, the lowbush blueberry is not, except for small roadside sales. The low growth habit and smaller berry size make hand-picking economically impractical unless labor costs are very low. Since lowbush blueberries are best used as an ingredient product, very little are used for the fresh market. A hand-rake is much more efficient than hand-picking and provides for a once-over harvest (Fig. 3). There are also several types and sizes of mechanical harvesters available that will reduce the cost of harvest (Yarborough, 2010).

FIGURE 3 Lowbush blueberry hand-rakes available at www.hubbardrakes.com (color figure available online).

CONCLUSIONS

The potential domestication of the lowbush blueberry was proposed in 1967 by Kender (1967). But because of the slow establishment and lack of rhizome production from cuttings, only one large planting has been established in China (Li and Wu, 2009). The ‘Novablue’ seed-propagated lowbush blueberry family has the advantage of lower cost of plant material with more rapid plant spread, while still maintaining sufficient genetic diversity to give the wild blueberry its unique flavor. This seed-propagated family has the potential to spread more rapidly and cover the entire field so that a greater productivity per hectare could be obtained and it could be pruned in an alternate year cycle to maintain its productivity. If established on the proper site and managed as the wild blueberry in North America, it has the potential to provide the basis for a successful domesticated lowbush blueberry industry that would provide a higher antioxidant level that could be used in high value-added nutraceutical products. However, the ultimate success of this industry will depend on the selection of suitable growing areas and the establishment of demonstration plantations to educate farmers to the appropriate cultural practices as described by He et al. (2009). It will also be important to recognize that some native pests could adapt to the lowbush blueberry, so monitoring and developing control strategies for new potential pests will also be necessary.

ACKNOWLEDGMENTS

This manuscript is publication number 3131 of the Maine Agriculture and Forest Experiment Station.