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Jimbean

Palms and zones

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Jimbean

Interesting topic, although labeling a zone does not really explain exactly what kind of cold a plant can go through.  Here's my guesses and personal experience, correct me if I'm wrong.

 

Sabal palmetto  8A

Sabal minor      7B

Sabal mexicana  8A

Sabal etonia       8A

Sabal brazoriensis   8A

Rhapidophyllum hystrix   7B

Serenoa repens     8B or 8A

Acoelorrhaphe wrightii 9B or 9A

Leucothrinax morrisii     10A or 9B

Thrinax radiata               10A

Coccothrinax argentata    10A or 9B

Roystonea regia                10A

Pseudophoenix sargentii    10A

Washingtonia robusta        9A

Arenga engleri                 9B

Caryota mitis                   9B or 10A

Latania loddigesii            10A

Bismarckia nobilis             9B or 9A

Livistona decora                 9B or 9A

Livistona chinensis             9A

Copernicia alba                   9B

Pritchardia thurstonii          11A

Pritchardia pacifica             11A

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Jimbean

Phoenix canariensis      8B

Phoenix dactylifera       8B

Phoenix reclinata          9A

Phoenix roebelenii       9B

Ravenea rivularis        10A or 9B

Archontophoenix cunninghamiana    10A

Archontophoenix alexandrae               10A

Cocos nucifera                             10B

Wodyetia bifurcata                     10A

Carpentaria acuminata              10A or 10B

Veitchia joannis                        10A

Veitchia arecina                          10A

Butia odorata                             7B

Adonidia merrillii                         10A

Ptychosperma elegans                10A

Ptychosperma macarthurii           10A or 9B

Syagrus schizophylla                     10A or 9B

Syagrus romanzoffiana                    9B or 9A

Dypsis decaryi                                 9B

Dypsis lutescens                             10A

 

Edited by Jimbean
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Xenon

Here's my $0.02. I think it makes more sense to make groupings rather than assign cutoffs. I made some notes for palms that get leaf damage at significantly higher temperatures than bud death.

Tier 1:

Pritchardia pacifica

Pritchardia thurstonii

Tier 2:

Cocos nucifera

Adonidia merillii

Tier 3:

Dypsis lutescens (hardiness of arborescent trunks)

Veitchia joannis

Veitchia arecina

Ptychosperma elegans

Ptychosperma macarthurii (hardiness of arborescent trunks)

Carpentaria acuminata 

Archontophoenix alexandrae

Latania loddigessi

Tier 4:

Dypsis decaryi

Syagrus schizophylla

Wodyetia bifurcata

Archontophoenix cunninghamia

Caryota mitis

Roystonea regia

Thrinax radiata

Leucothrinax morissii

Coccothrinax argentea

Tier 5:

Ravenea rivularis (bud hardiness)

Phoenix roebelenii (bud hardiness)

Arenga engleri (hardiness of arborescent trunks)

Acoelorrhaphe wrightii (hardiness of arborescent trunks)

Tier 6:

Copernicia alba

Phoenix reclinata (hardiness of arborescent trunks)

Tier 7:

Syagrus romanzoffiana (bud hardiness of hardiest forms)

Livistona decora

Bismarckia nobilis (bud hardiness of hardiest forms)

Tier 8:

Phoenix dactylifera (bud hardiness)

Washingtonia robusta (bud hardiness)

Tier 9:

Livistona chinensis (bud hardiness)

Tier 10:

Sereona repens

Butia odorata (bud hardiness)

Phoenix canariensis (bud hardiness)

Tier 11:

Sabal palmetto

Sabal mexicana 

Sabal xbrazoriensis

Sabal etonia (?)

Tier 12:

Raphidophyllum hystrix

Sabal minor 

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kinzyjr

I like @Xenon's tiered approach.  The zone system, especially high 9b/low 10a, gets really ambiguous.

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Xerarch

I think the USDA zones above are pretty good, you could argue about moving some of them a half zone but that's the issue, too much depends on location/duration/wind/humidity/frost, etc. I saw palms killed here during last year's freeze that would barely have suffered a scratch in the desert southwest at the same temperature. 

I also like Xenon's tier grouping, that's a great idea.

One more thing to mention related to cold hardiness that is not easily captured in these types of systems is speed of growth.  For example, Washingtonia robusta and Phoenix dactylifera exhibit about the same-ish hardiness to cold. But W robusta grows so fast it can overcome abuse faster and more regularly. If both robusta and dacty suffer equally severe damage every year, the robusta will bounce to full crown in short order, while the dacty will slowly decline year after year unless it gets a reprieve that lets it replace the crown.  So, in that sense, it's as if W robusta is more cold hardy.   

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tim_brissy_13
1 hour ago, Xerarch said:

I think the USDA zones above are pretty good, you could argue about moving some of them a half zone but that's the issue, too much depends on location/duration/wind/humidity/frost, etc. I saw palms killed here during last year's freeze that would barely have suffered a scratch in the desert southwest at the same temperature. 

I also like Xenon's tier grouping, that's a great idea.

One more thing to mention related to cold hardiness that is not easily captured in these types of systems is speed of growth.  For example, Washingtonia robusta and Phoenix dactylifera exhibit about the same-ish hardiness to cold. But W robusta grows so fast it can overcome abuse faster and more regularly. If both robusta and dacty suffer equally severe damage every year, the robusta will bounce to full crown in short order, while the dacty will slowly decline year after year unless it gets a reprieve that lets it replace the crown.  So, in that sense, it's as if W robusta is more cold hardy.   

The other factor for those of us in temperature climates is cool hardiness as opposed to absolute cold hardiness. A. alexandrae which is in Tier 3 is a trouble free grower here for example, but most of tier 4 will not grow at all. Bismarckia which is in tier 7 is marginal. Some palms just need sustained warmth to grow even if the temperature never approaches their absolute hardiness limit. 

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James B

I would put Archontophoenix Cunninghamiana and Maxima as solid 9B palms.

I would also put Roystonea Regia and Wodyetia as 9B as well.

This is based on their performance in my yard in North Rancho Cucamonga CA at 1600 ft elevation. 

The USDA zones can have their limitations concerning level of sunlight, humidity, and duration of winter are concerned. A comparison of Socal vs Central Florida is the perfect example. Central Florida gets colder than it does here but our winters last much longer which is the bane of palms like Cocos which can survive 9B Orlando but succumb to 10A Socal winters. 

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James B

Perhaps a Zone standard for Mediterranean vs Subtropical climates separate of one another would actually be very helpful. 
 

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Xenon
1 hour ago, James B said:

The USDA zones can have their limitations concerning level of sunlight, humidity, and duration of winter are concerned. A comparison of Socal vs Central Florida is the perfect example. Central Florida gets colder than it does here but our winters last much longer which is the bane of palms like Cocos which can survive 9B Orlando but succumb to 10A Socal winters. 

Agree with the heating requirement, growth rate and chill tolerance mentioned by you and others.

Slight nitpick on the Orlando comparison as urban Orlando has been de facto zone 10 for a while (at least as long as the coconuts have been growing). Urban Orlando has only seen one freeze in the last 10 years.

That's another "problem" with using zones, people will often claim XYZ palm will grow in 9A, 9B etc simply based on the map but their de facto zone is higher i.e there is no way coastal St Augustine is an archetypal 9A or urban Orlando is an archetypal 9B. There's also a bias in Florida towards the warmest end of 9B based on the USDA map (because that's where most of the population centers are) so when people tout "9B hardiness" it really means "9B based on the map but numerically zone 10 and nowhere near the middle of 9B (27.5F)". This results in inflated hardiness ratings for things like Beccariophoenix alfredii imo, especially considering much of Florida has had a warm streak for a while. 

 

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