What are chill hours for fruit trees?
Chill hours and chill units both refer to the total amount of time a blossoming fruit tree needs to be exposed to cold temperatures so that it can flower and fruit.
How to use chill hours to plan and maintain the health of your crops.
Knowing the required number of chill hours allows growers to plan ahead and account for which stage of the tree’s life cycle it’s in.
Insufficient chill units can result in reduced fruit set, fruit quality, delayed foliation and extended bloom periods. To combat insufficient chill hours growers may choose to promote flowering and vegetative bud break growers using Rest Breaking Agents (RBAs), bringing the tree out of its dormancy stage.
On the other hand, too many chill units can cause trees to flower early, exposing the sensitive new shoots to frost damage, causing damaged foliage and killing fruit. Growers may use foggers, sprinklers, and fans to prevent frost and set frost alerts in Jain Logic to reduce the risk of frost damage ruining their yield.
How do we calculate chill hours for fruit trees?
Our platform Jain Logic allows you to select one of the following methods; Threshold and Utah.
- Threshold Method: Any hour with an average temperature under the supplied threshold is considered a chill unit. Example: If our set threshold is 7°C, every hour below 7°C will be equal to one chill unit.
- Utah Method: A temperature range is used to calculate chill units. The range determines how many chill units to apply below a set range. It also deducts for when temperatures are above a threshold range, from the accumulative chill units.