You might see the term “chill hours” when looking at fruit trees online or notice it on a plant tag when shopping for them. If you’re giving serious consideration to starting a fruit tree in your yard or even planting a small orchard, you may have looked up the term. There you were confronted by another unfamiliar term– vernalization — and often a complicated description.
If you want to grow
some fruit trees and need some simple information about plant chill hours
and why they’re important, continue reading. We’ll attempt to break it down
here in simple terms that are easy enough for anyone to understand.
What are Chill Hours?
Chilling hours are basically the hours between the temperatures of 34 and 45 degrees F. (1-7 C.) in autumn that will reach the tree. These are calculated for when the fruit tree is preparing itself to enter dormancy for winter. Hours when temperatures normally reach 60 degrees F. (15 C.) are not included and not counted as chill hours.
Many fruit trees require a time of
exposure to temps that are low, but above freezing. These temperatures are
required for the trees to perform as we expect them to, like producing flowers
that become fruit.
Why are Chill Hours Important?
The proper minimum of chill hours
is necessary for flowers and subsequent fruit to form on the tree. They tell
the energy within the tree when to break dormancy and when to change from
vegetative growth to reproductive. Hence, the apple
tree blooms at the appropriate time and the fruit follows the flowers.
Trees that do not get the proper chilling hours may develop flowers at the wrong time or none at all. As you know, no flowers mean no fruit. Flowers that develop too early may be damaged or killed by frost or freeze. Improper flowering may create a reduced fruit set and reduced fruit quality.
Vernalization is another term for this process. Various trees have different chilling hour requirements. Nuts and most fruit trees need a required number of chill hours. Citrus and some other fruit trees don’t have a chill hour requirement, but most do. Trees with low chill hour requirements are available.
If you need to know how many chill
hours a new tree needs, you can refer to the tag in the pot or you can research
and go a little further. Most places that sell fruit trees purchase them
wholesale by the USDA hardiness zone where the store is located. If you are not
in the same zone or just want confirmation, there are places to look and calculators
are available online. You can also contact your county
extension office, which is always a good source for information.
You might see the term “chill hours” when looking at fruit trees online or notice it on a plant tag when shopping for them. If you’re giving serious consideration to starting a fruit tree in your yard or even planting a small orchard, you may have looked up the term. There you were confronted by another unfamiliar term– vernalization — and often a complicated description.
If you want to grow
some fruit trees and need some simple information about plant chill hours
and why they’re important, continue reading. We’ll attempt to break it down
here in simple terms that are easy enough for anyone to understand.
What are Chill Hours?
Chilling hours are basically the hours between the temperatures of 34 and 45 degrees F. (1-7 C.) in autumn that will reach the tree. These are calculated for when the fruit tree is preparing itself to enter dormancy for winter. Hours when temperatures normally reach 60 degrees F. (15 C.) are not included and not counted as chill hours.
Many fruit trees require a time of
exposure to temps that are low, but above freezing. These temperatures are
required for the trees to perform as we expect them to, like producing flowers
that become fruit.
Why are Chill Hours Important?
The proper minimum of chill hours
is necessary for flowers and subsequent fruit to form on the tree. They tell
the energy within the tree when to break dormancy and when to change from
vegetative growth to reproductive. Hence, the apple
tree blooms at the appropriate time and the fruit follows the flowers.
Trees that do not get the proper chilling hours may develop flowers at the wrong time or none at all. As you know, no flowers mean no fruit. Flowers that develop too early may be damaged or killed by frost or freeze. Improper flowering may create a reduced fruit set and reduced fruit quality.
Vernalization is another term for this process. Various trees have different chilling hour requirements. Nuts and most fruit trees need a required number of chill hours. Citrus and some other fruit trees don’t have a chill hour requirement, but most do. Trees with low chill hour requirements are available.
If you need to know how many chill
hours a new tree needs, you can refer to the tag in the pot or you can research
and go a little further. Most places that sell fruit trees purchase them
wholesale by the USDA hardiness zone where the store is located. If you are not
in the same zone or just want confirmation, there are places to look and calculators
are available online. You can also contact your county
extension office, which is always a good source for information.