Determining Plant Cold-Hardiness

Discussion in 'HortForum' started by Junglekeeper, Aug 19, 2004.

  1. Junglekeeper

    Junglekeeper Esteemed Contributor 10 Years

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    Vancouver BC Canada
    Is there a safe rule-of-thumb one can apply to determine how low the temperature can go without causing severe damage to a plant?

    The USDA plant hardiness zones are useful as a starting point. However it may not be good enough for certain plants. Case in point. Murraya paniculata is rated as a zone 10-12 which suggests it would survive to -1C. This contradicts warnings that the plant would be killed by temperatures below ~12C -- much higher than zone 10 minimum. Contrast with Aglaia odorata which is also rated a zone 10-12 but its minimum temperature is ~2C which is much closer to the zone minimum. So how can one be sure?

    Of course the proper way is to research each plant individually. However cultivation requirements for some plants, particularly lesser known tropicals, are hard to come by and the trial and error method could result in dead plants. Any help?
  2. Hardiness

    Possibly you are thinking the temperature ranges given for each Zone indicate absolute minimum temperatures, rather than average annual minimum temperatures. If it is to be long-lived in a given Zone, a plant needs to be hardy to temperatures quite a bit lower than average for that Zone.

    If you survey references you will find variation in Zones assigned to the same plant. Apart from those that may simply be incorrect, other discrepancies will probably be due to induced variations in hardiness due to environment, such as summer conditions (Zone 7 after a hot summer in the SE or SW USA, Zone 9 in cool summers of PNW/SE BC), as well as ingrained variation in hardiness shown by wild species of differing provenances.

    There is no substitute for local experience.

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