Blueberry Plants – Chilling Requirements for Blueberry Production


After the blueberry harvest the blueberry bushes start to develop the next seasons fruit buds. They then start preparing for the cold winter weather. If cold conditions do not arrive suddenly the pants will go into dormancy and with little to be concerned about. All blueberries varieties require about a certain number of hours of chilling. Above freezing temperatures but below about 45 F are needed by the blueberry plants to meet their chilling requirements. In the fall the temperatures will be cool enough so the plants can begin to accumulate needed chilling hours. The blueberry plant will not produce fruit the next season if the chilling need is not accomplished. Long periods of below freezing weather simply delays the finishing of dormancy but does not add to the chilling requirements. After the plants chilling need is accomplished the plants will begin growth when the conditions for growth become right. It is for this reason that blueberry plants may be able to be grown indoors because of their requirement for chilling hours.

Chilling hour requirements

Everyone who is interested in growing their own fruit will eventually be faced with the issue of chill units (CU). This is especially the case when growing blueberry plants in the south. Chill hours are the hours accumulated where temperatures are between 32 degrees F to 45 degrees F. Some other fruits such as Peaches and Apples that have evolved in colder climates have chill requirements.

The amount of cold temperature the plant needs to continue normal growth in the spring following the winter season is usually referred to as the plant’s chilling requirement. Different blueberry plants vary widely in their requirement. Blueberry producers need to take into account the blueberry plants chilling requirements when they select them for planting.

The chill time is amount of cold temperature required to meet the chilling time required by a blueberry plant determine the area in which they can be planted. Temperatures between approximately 35 to 45 degrees F supply most of the chilling needed by blueberry plants. The most effective chilling temperature is 45 degrees F. Temperatures below 32 degrees F add little or nothing to the chilling needs being received by the plant

Depending on the variety, blueberry plants need between 150 and 2,000 hours of exposure to temperatures from 35 [degrees] F to 45 [degrees] F are needed to meet the plants chilling requirement and for growth resumption and bud-break in the spring. Chill time does not accumulate at below freezing temperatures. This means that temperatures below freezing to not count toward needed chilling hours.

Chilling requirements for some Southern Blueberries.

Southern highbush varieties are blueberry plants that grow from zones 6 through 10. They require much less chill hours some other varieties. Some need only 150 to 200 chill hours to produce fruit. This means you can grow blueberries in the southern United States.

Some southern blueberry bush varieties and their chilling requirements are listed in order of increasing times for chilling below.

Sunshine blue 150 hours chilling time

Jewel 200 hours Chill time requirement

Sharpblue 200 hours Chill time requirement

MISTY 250 hours Chill time requirement

Emerald 250 hours chilling hours requirement This is excellent choice for the warmer areas, because the Southern Highbush plants only require 250 chilling hours to produce record-setting quantities of very large blueberries.

O’Neal 400 hours Chill time requirement

Jubilee 500 chilling time requirement

Ozarkblue 800 hours Chilling time requirement

Of the Southern Highbush, as seen in the above list, Sunshine Blue Blueberry plants are the least demanding in terms of chilling requirements. You need a minimum of 150 Chill Hours to grow one.

Sunshine Blue has a lot of good characteristics. Sunshine Blue is a semi-dwarf, with pretty hot pink flowers that change to white in spring. It yields large crops of delicious blueberries. It can tolerate higher pH soils better than many other blueberries and it is self-pollinating. The chilling requirement of 150 hours is lower than any other blueberry plant making it right for Southern climates, but it is also astonishingly cold-hardy and makes a great addition to gardens and patios all the way up to Chicago.

Rabbiteye Varieties

Rabbiteye blueberries are native to the southern United States. They have been in commercial cultivation for over 100 years and in recent years better varieties have been developed. The Tifblue Blueberry bush was a breakthrough in hybridizing rabbiteye blueberry plants. The hybridized rabbiteye cultivars initiated the rise of the remarkable rabbiteye blueberry commercial trade. This has resulted in a remarkable agricultural growth in blueberry production that is reshaping the economy of the South. The rabbiteye blueberries have chilling hour requirement from 350 to 700 hours. Rabbiteyes flower earlier but ripen later than southern varieties. The shelf life of harvested rabbiteye blueberries is outstanding and generally better than highbush blueberries.

Some of the popular rabbiteye blueberry bush varieties and their chilling requirements listed in order of increasing times for chilling are listed below.

BRIGHTWELL. 350-400 chill hours requirement.

Climax – 450 – 500 chill hours requirement.

PREMIER 550 chill hours requirement.

TIFBLUE 550-600 chill hours requirement.

POWDERBLUE 550-650 chill hours requirement.

Northern varieties

Northern high bush varieties need a large amount (usually 800-1,000) of chill hours to produce blueberries. These blueberry plants are that grow in zone 3 through zone 7.

If a blueberry bush does not obtain the necessary number of chill hours it may and often will grow fine but will not make any blueberries.

Source by Harold Stewart

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