0000 - Cold Hardiness Observation Master Data

September 19

Overview

The PalmTalk forums contain thousands of observations on the cold tolerance from a variety of locations and climates. One of the primary difficulties in determining cold hardiness of a particular species or variety of palm is that observations vary greatly, even at the same temperature in the same location. Therefore, hardiness can be more accurately expressed as a probability rather than in absolutes.

The goal of the attached list is to more accurately calculate the probability and degree of damage one could expect from a freeze on a particular species or variety of palm by consolidating the available data into one document. This list is provided without any warranty or guarantee, expressed or implied.

Several factors can influence the effect of a low temperature on a palm. These include:

Ultimate low temperature
Duration of the freeze – time below 28F, time below 32F, number of days with low temperatures
Weather before freeze – was it warm and sunny with plants in active growth or were the palms given time to harden off by a slower onset of below average temperatures?
Advective vs. Radiational freeze? – Advective freezes are usually more damaging due to wind chill and less stratification.
Overhead canopy/protective siting – Was the plant out in the open or under cover? Are there structures or plants being used as windbreaks? Canopy typically mitigates frost formation during a radiational freeze and windbreaks lessen the windchill effect during an advective freeze.
Frost – did frost form?
Wet vs. Dry – did the freeze come with wet/damp soils from a preceding rain storm or was the ground dry?
Size and overall health of the plant – A healthy, mature palm is usually more likely to survive than a palm that was juvenile or unhealthy.

Another consideration is how long a grower waited after the freeze to report damage. Sometimes damage will manifest itself weeks or months after the actual freeze. If a report comes too soon after the freeze, then the report could change.

When possible, the list is an attempt to consolidate observations into an easily searchable list that captures as many of the factors influencing damage and survival. Because new observations are constantly being added, this list is a perpetual work in progress.

Credits

The following resources were and are being used to build this list:

http://www.trebrown.com/palms_arecaceae.php - Used to build the initial list of palms since it is fairly complete and up to date. Observations added to the list were checked against this list. If the check failed, it was either because the name given is a synonym or another name needed to be added to the list.
http://www.theplantlist.org – Used to check for synonyms of the palm species and varieties in the Trebrown list when no match could be found.
www.palmpedia.net – Invaluable as a tool to check for synonyms and species potentially not listed by the Trebrown list.
http://www.cfpacs.org/freezes-central-florida/ - The freeze observations at this site were added to this list and are also posted in the PalmTalk forums in the Freeze Damage Data section at the following URL: https://www.palmtalk.org/forum/index.php?/topic/40159-aaa-florida-general-palm-hardiness-data/
https://www.bg-map.com/noblick.html - The two tables available here were merged and duplicates were removed before expanding the list giving each observation its own row in the table. When the name of the palm in this list could be identified as a synonym, the name in this list was preserved in the Description field in brackets []. There is a full list of citations at this page that includes several active forum participants.
https://www.palmtalk.org/forum/ - Some of the hardiness observations throughout the forum have been loaded into this list. This portion will always be a work in progress.