Apple Chilling Info How Many Chill Hours Do Apples Need

Most apple varieties need 500-1,000 chill hours or temps below 45 F. (7 C.) but there are some low chill varieties available that need no more than 300 chill hours. Low chill varieties need less than 700 chill hours and can withstand hotter summers than other varieties.

How do you calculate chill hours for fruit trees?

One way to calculate chill hours is to count the number of hours with a temperature below 7°C (45°F). A slightly more accurate model excludes hours below freezing (as these do not contribute towards dormancy) and only counts those spent between 0°C (32°F) and 7°C (45°F).

What is chilling requirement for fruit trees?

Typically, temperatures between 32°F and 50°F can help fulfill the chilling requirement of many plants, but the most efficient temperatures for satisfying a plant's need for cold are between 32°F and 45°F. When temperatures dip below 32°F, very little, if any, chilling is received by the plant.

How cold can apple trees tolerate?

The cold hardiness of flower buds is genus- and variety-dependent: peach, minus 10˚ F; cherry, minus 15˚ F; apple and pear, minus 25˚ F to minus 30˚ F.

Do apples need frost?

Apples can withstand light frosts but a frost is not needed to complete the ripening process. When temperatures fall below 28 degrees, ice crystals can form within the cells.

What are chilling hours for fruit trees?

WHAT ARE CHILL HOURS: Chill hours are the cumulative number of hours of temperatures lower than 45°F that are required by deciduous fruit and nut trees for fruit production. The hours are tracked during the traditional dormant season, measured from November 1 to February 28/29.

How many chill hours does zone 9b get?

Chilling Hours

Zone 8a 700+ Chill hours includes southern SC west to central TX	Premier, Climax Blueberry
Zone 9b 110-310 Chill hours includes extreme south TX	Anna, Dorsett Golden Apple, FlordaPrince, FlordaBest Peach, Tropic Beauty, Tropic Snow Peach, Sunhome Nectarine, Sharp, Misty, Gulf Coast Blueberry

What temperature is considered chill hours?

Chill Hours (sometimes called Chill Units) are an approximation of how many hours of weather between 32 degrees and 45 degrees (F) a plant requires to properly go dormant so it can wake up and blossom and/or set fruit. Some plants, like fruit trees and certain flowers, require a minimum number of chill hours to thrive.

What are chilling requirements for crops?

A plant's chilling requirement is the number of hours the plant must be exposed to temperatures between 32 F and 45 F before the plant breaks dormancy. (Times when the temperature drops below 32 F or rises above 45 F don't count toward the chilling requirement.)

What is the chilling temperature?

Chilling is the application of temperatures in the range of 0°C to 8°C, i.e. above the freezing point of the food, while freezing uses temperatures well below the freezing point, conventionally below 18°C. The difference between the two processes goes beyond the difference in temperature.

What climate is best for apple trees?

The apple is a hardy, deciduous woody perennial tree that grows in all temperate zones. Apples grow best where there is cold in winter, moderate summer temperatures, and medium to high humidity.

How do I protect my apple trees from freezing?

To protect smaller trees, put stakes in the ground around the tree and drape it with a sheet, burlap, fruit tree frost blanket, plastic, or other cloth during the day before the freeze. Make sure the cover goes all the way to the ground. A cover is used to hold heat around the tree.

How do I protect my apple trees from frost?

Fruit bushes, very dwarfing fruits trees and wall-trained fruits are a little easier to protect. Drape two or three layers of row cover fabric over your plants, or use plastic, sheets or any other light material you have to hand. Make sure it extends to ground level to trap warmer air next to the tree.

How cold is too cold for apples?

Apple fruit will withstand up to 4 hours at 28°F before serious injury occurs. Recovery depends not only on the extent of freezing, but also the rate of thawing. The fruit tissues of apples have sugar and other constituents that lower the freezing point of fruit below 32°F.

How long can you leave apples on the tree?

Apples should be harvested when they are physiologically mature but before their peak of ripeness. Apples for eating fresh or for short-term storage (2–3 weeks) should be left on the tree until they are fully ripe. Store only sound fruit that is free from insect or disease damage.

Is Frost bad for apples?

Unless the temperature dipped below 22-23 degrees F. (-5 C) or lasted an extended period of time, it is quite likely the apples will survive for harvesting. Once the apples thaw, inspect them for damage.

Do pomegranates need chill hours?

The majority of pomegranate varieties do not require winter chill hours, with the exception of a few cold-hardy cultivars. ... Pomegranates are extremely heat tolerant, and perform best when temperatures are above 85 degrees F for at least 120 days a year.

What is low chill for fruit trees?

Generally, fruit growers have most success with varieties that have stated chilling requirements similar to the chilling typically received at the planting location: “high chill” varieties (800-1,000+ hours) for cold winter climates, “low chill” varieties (500 hours and less) for warm winter climates.

What are chill hours for blueberries?

Blueberry bushes need a minimum number of chill hours by variety each winter to enhance their fruiting. Chill hours are defined as hours less than 45°F but above 32°F. If a blueberry bush doesn't experience enough chill hours in the winter, the flower buds might not open at all in spring, or they might open unevenly.

When can I plant in Zone 9b?

As a general rule, most vegetables should be started indoors 6-8 weeks before your last frost date. In zone 9b, this would be around January 1st – January 18th. Or if you're directing seeding vegetables into the garden, most seeds should be sown after your last frost date.

What are the best fruit trees for Zone 9?

Zone 9 Fruit Tree Varieties

Owardi satsuma mandarin orange (Citrus reticulata 'Owari')
Calamondin (Citrus mitis)
Meyer lemon (Citrus x meyeri)
Marumi kumquat (Citrus japonica 'Marumi')
Trifoliate orange (Citrus trifoliata)
Giant pummelo (Citrus pummel)
Sweet Clementine (Citrus reticulata 'Clementine')

How many chill hours does Zone 10 get?

Chilling requirement is a concern for USDA zones 9B and 10, predominately in Southern and coastal regions where chilling hours average 100 to 600 per year. If you are within this area, take note of the chilling requirements listed for fruits and choose accordingly.