Blueberry plants

The High Chill Blueberry is also called Northern Highbush. It is traditionally a strait Vaccinium corymbosum native to the northern states of the United States and Canada. This species was first selected in the early 20th century by breeding pioneers Elisabeth White and Frederic Coville.

Today, most recent varieties contain some interspecific genes responsible for added firmness and shelf life.

The chilling requirement* of Northern Highbush is over 1000 hours. These varieties generally perform well in oceanic, temperate and continental climates.

* It is expressed in Hours and determinates the amount of cold temperatures necessary for fulfilling the dormancy requirement of one variety. The “vegetative zero” is commonly accepted to be somewhere between 7 and 8°C. The number and consistency of hours below this temperature will determinate the chilling available in one region.) 

The Mid-Chill Highbush Blueberry is an interspecific hybrid with an intermediate chilling requirement*.
Its cold hardiness is usually less than the traditional northern highbush, but other desirable traits such as superior firmness or higher yield potential are usually present.

* It is expressed in Hours and determinates the amount of cold temperatures necessary for fulfilling the dormancy requirement of one variety. The “vegetative zero” is commonly accepted to be somewhere between 7 and 8°C. The number and consistency of hours below this temperature will determinate the chilling available in one region.) 

Also known as the Southern Highbush, the Low to Zero chill Highbush Blueberry is an interspecific hybrid developed by the University of Florida. The main idea behind it was to create a blueberry highbush for growing blueberries in lower latitudes, thus extending the window and availability of fresh blueberries. As some good surprises can happen, breeders have found over time that genes responsible for added firmness and shelf life, or Brix, have come along with the desired low chilling characteristics. Some varieties have no chilling requirement* at all and can be grown in tropical to subtropical regions. Other varieties have some chilling requirement and will do well in a Mediterranean climate. Southern Highbush Blueberry is generally pruned very severely after harvest so that the yield is carried entirely by 1-year-old canes.

* It is expressed in Hours and determinates the amount of cold temperatures necessary for fulfilling the dormancy requirement of one variety. The “vegetative zero” is commonly accepted to be somewhere between 7 and 8°C. The number and consistency of hours below this temperature will determinate the chilling available in one region.) 

This cousin (Vaccinium virgatum/ syn: Vaccinium Asheï) of the traditional northern highbush is native from the southern states of the U.S. and has naturally low chilling requirements with limited hardiness. Most Rabbiteye varieties are late ripening and have the economic benefit of off-season (September/October) production in regions where the fruit can ripen sufficiently late without being exposed to severe winter frosts.