Welcome to the regional Ontario Tender Fruit bud cold hardiness webpage -TenderFruitAlert. The information contained on this webpage is to provide tender fruit growers with comparative levels of bud hardiness for different fruit types/commodities (peaches/nectarines, plums, apricots) and specific cultivars of those commodities at different locations throughout the dormant period (mid-October to mid-April). Monitoring bud cold hardiness throughout the dormant period is an invaluable tool to assist tender fruit growers in managing winter injury. The data provided from this database will allow growers and researchers to see the level of cold hardiness of the  buds of different types of tender fruit within a specific area at a specific date. Cold hardiness is not static but varies throughout the dormant period and can be influenced by environmental conditions as well as the genetic potential of the different types of tender fruit commodities and cultivars. Bud sampling and testing is done throughout the entire dormant season to monitor cold hardiness through the acclimation, maximum hardiness, and deacclimation periods. This ever-changing bud hardiness data is important in determining when wind machine use or other freeze avoidance methods are useful to protect the buds from winter injury.
This research is also fundamental to understanding when, during the dormant period, bud injury may have occurred and  how growers can ensure that maximal cold hardiness is achieved for the dormant season. Climatic conditions specific to each geographical area are variable and sampling from multiple locations is important.  Therefore, regional sampling can account for differences that may lead to different rates of acclimation and deacclimation as well as maximum cold hardiness levels. This database of information will assess cultivar variations within a commodity group, regional variations in cold hardiness over multiple years and assist growers and researchers across Ontario in developing effective and efficient winter protection strategies.
This initiative is supported by funding through the Growing Forward 2 Project Implementation program of the Agricultural Adaptation Council (AAC). This outreach project is a collaboration between the Ontario Tender Fruit Marketing Board, AAC, Brock University, KCMS Applied Research and Weather Innovations.

Description of the Project

A system for differential thermal analysis (DTA) has been constructed to assess cold hardiness of tree fruit buds.  The equipment used to assess hardiness is identical to the system being used for grapevine bud hardiness studies and is based upon a procedure developed and used at Washington State University and is  similar to systems being used at other research facilities in the US and Canada.  This DTA / freezer unit incorporates custom designed sample trays with a  programmable freezer and a data acquisition and data management system developed at Brock University.  
The hardiness of tender fruit buds is estimated by sampling shoots from orchards periodically throughout the dormant season, placing them on thermo-electric modules hooked to data acquisition systems, then subjecting them to artificial freezing regimes.  Cooling starts at 4oC, then air temperatures are dropped slowly 3oC/h over 13 hours to -40oC. When water freezes (changing state from a liquid to a solid), it releases heat, so as buds are gradually subjected to colder, freezing temperatures, this equipment is able to detect these releases of heat which is an excellent indicator that the cells within the flower buds are damaged.  Predictions can then be made about air temperatures that may cause cold damage in subsequent days. This information helps researchers and growers decide whether wind machine use is necessary based on upcoming weather forecasts.  Currently there are eighteen (18) orchards being routinely sampled from in Niagara (Figure 1) and six (6) orchards sampled on a monthly basis in other productions areas in the province (Simcoe, Blenheim & Arkona areas).

Figure 1 – Map of the Niagara area sampling locations (blue dots)
Periodically throughout the dormant season, at the same time of sampling for bud hardiness, a second set of samples are collected from each location and manually cut to determine flower bud survivability.  This method is very commonly used to assess bud survival and is based on discolouration (browning or oxidation of injured cells) of flower bud tissues that occurs after low temperature injury.  Healthy flowers maintain their green colour while injured cells rupture due to internal ice crystal formation and turn brown. To assess buds for survival, samples are collected in the field then held  at room temperature for 24-48 hours to allow the oxidative browning process to take place. After the holding period, the buds are then cut to determine the number alive and calculate percent survivability (Figure 2).

Figure 2 - Cut flower bud of peach (cv. Vivid) showing a dead bud on the left and an alive bud on the right





This project was funded in part through Growing Forward 2 (GF2), a federal-provincial-territorial initiative.

The Agricultural Adaptation Council assists in the delivery of GF2 in Ontario.