Cold Hardy Palms – The Best Palm Tree Species for Cold Weather

THE BASICS ON LEARNING WHICH PALMS WILL TOLERATE YOUR WEATHER – SELECT THE BEST COLD TOLERANT SPECIES 

by Phil Bergman

Introduction

Cold hardy palms – the best palm trees species for cold weather – is described here.  There are a couple of basic things to consider when selecting cold hardy palm species to grow in your locality.  First is to know how cold you get.  Second, learn the cold tolerance of the various species.  The final thing is to learn how to give your palms good culture and cold protection if needed.  This applies to periods before, during, and after the cold weather.

How Cold Do You Get?  The Most Important Question

When you select palm tree species to grow, realize that your coldest night’s low temperature determines what you can grow.  You should begin to know and have your low temperatures on the tip of your tongue.  The major limiting factor in the successful growing of palms is the degree of cold weather that any given palm species will see during the winter.  Factors such as intensity of sun, presence of summer heat (or lack of it), and humidity are also very important.  But, cold exposure is the most limiting factor.  So, the goal is to know how cold you actually get on the coldest nights.  Try to get a maximum-minimum (high-low) thermometer.  Most palm nurserymen would rather you tell them your low temps than quoting “climate zones”, as the latter are unreliable and quite variable.  The best way to determine how cold your garden gets is to purchase a maximum-minimum or hi-lo thermometer.  They are quite simple to use.  Place it in the garden in the shade.  Although you can reset it with a magnet, it might be best to just leave it alone for the lowest temperature over a longer period.  

When you go to buy plants, the most valuable information you can give to a nurseryman is “how cold you get”.  It’ll make his recommendations easier and save you losses on a cold winter. 

Getting Good Advice

If you look in a typical palm book, you will see statements such as “this species is well suited for temperate areas”.  What does that mean in your case?  Its not very helpful.  Words like temperate and semitropical and mild areas are sometimes more deceptive than helpful.  Yet these are the types of statements palm books make about growing different palm species.  All you want to know is “will it grow for me?”    

Nursery staff assist customers in finding the best species for his area  To answer this question for you, a palm grower depends on his experience and the experience he’s gathered from others over time.  For the past 35 years I’ve gathered cold tolerance information from my customers, my own growing experience, Internet discussions, and from meetings and conferences I’ve attended.   The knowledge that experienced growers attain becomes almost second hand to them.  The Palm Society of Southern California has, for years, pooled information and produced a publication about cold tolerance of many species.  The usefulness of this information is to let us all know which species have the best chance to survive in one’s garden, especially if he lives in a very cold area.    

Therefore, when you know how cold you get, talk with a palm nurseryman, an experienced palm enthusiast, or someone who really knows his stuff. This will keep you out of trouble and make your growing a lot easier.  Unfortunately, home improvement centers and general nurseries typically don’t know much about the species and specifically about their cold tolerance.  Most palm specialty nurseries will know which species are best for your area.  It might be wise to trust their opinions and recommendations.      

Be Realistic – Once you are armed with information about your cold weather and have a reliable and informed nurseryman for your plant material, pick the appropriate species for your area.  I can’t tell you how many times a customer has enthusiastically told me that their particular area is a “special microclimate” and that they can grow things no one else can grow.  Perhaps this is true, but palms show very predictable damage when exposed to certain temperatures.  Certainly there are a lot of variables but   Don’t expect the impossible.  Be realistic in your expectations.

 In Our Area Certain Palms, Including the Coconut Palm, Do Not Survive Outdoors

Yes, there are a few survivors throughout the entirety of Southern California.  But, as a very reliable rule, Cocos nucifera, will eventually die in Southern California from our cold weather.  This doesn’t mean you cant try, but the chances are you will fail.  The same applies to a lot of sought after species.  Cyrtostahcys renda, the Red Sealing Wax Palm, attracts many enthusiasts because of its dramatic red trunks.  No, it will not survive in cold weather.  It predictably dies at about 47 degrees Fahrenheit.  Archontophoenix cunninghamiana, the King Palm, dies at about temperatures below 24 to 25 degrees.  The typical Queen Palm dies at about 18 degrees.  So, if you know your garden gets down to 5 degrees, don’t think you’re going to keep alive any of the above species.  Plant palms that will predictably grow in your area.  If you like to make lists of palms that appeal to you (typically on the Internet or with books), bring that list to your local grower and he can tell you which ones to eliminate.  Many of our customers do just that.  Some specifically are searching for cold hardy palms.  If they aren’t sure, they might bring in a list of twenty-five plants, and we immediately eliminate some because they probably wont survive in his area.  Remember, the first things I ask a new visitor to the nursery is “where do you live and how cold do you get”.  Below are two palm species you may not be able to grow.

What About Microclimates?

It is true that microclimates are very important and do exist.  Being on a ridge is better than being in the bottom of a cold valley.  Overhead canopy is also protective from the cold.  Such canopy can keep interior garden temperatures much warmer on a cold night, sometimes even 10 degrees F. warmer.  Large rocks jutting out of the ground can maintain the previous days warmth and release this warmth during the night.  Morning exposures to sun can quicken the re-warming of the plants after a cold night.  All of these things are important.  But, the cold that you measure (even in the microclimate areas) is the low.  This determines which species you can grow.  Another recommendations is to look around in your area.  If your neighbors tell you that a given species has died in the winter despite three attempts, perhaps that species is bad for you.  On the contrary, if people in your neighborhood are growing well a given species, the chances are you can grow it as well.  Except for the rare “warmer” individual microclimates, most neighborhoods share a similar low winter temperature. Cocos nucifera, a poor choice for all but the most tropical areas.

Remember To Acclimate Your Palms

Lets say you’ve done your homework, you know how cold you get and which plants to purchase.  When you purchase your plants, remember to acclimate them to your area.  A cold tolerant palm may need a little help getting ready for your area.  If it was raised in a greenhouse, it might need a little protection before its ready for your cold or your sun.  Such a plant could be placed under a tree or next to the house for its first few months.  This is especially true if you’ve purchased it during the coldest part of the year.  Don’t just challenge the plant.  Rather, acclimate it slowly into the cold or full sun that you have to optimize your success.

How To Use This Information

Use the following cold tolerance information as a general guide.  There is no crystal ball in the plant world.  The following information will help you pick the right species for your area.  But, it is not gospel.  It is not a guarantee.  It is meant to be helpful information only.  With this in mind, please read the next session.  The next section of this article is where I discuss the species and which would be right for you.

Palms for the Coldest Areas 

Palm Trees For Extremely Severe Cold Weather   (15 degrees F. and lower)

 Although a comprehensive list of all species is not possible here, there are many palms that do tolerate some degree of cold.  We shall break it down into three groups:  Palms for extremely severe cold weather, palms for moderately severe cold weather, and palms for  cold weather with definite freezes.  Obviously, plant species from a colder group would be grown easily by people who find themselves in a warmer grouping.  Remember that it’s all about your lowest temperatures, not your climatic zone

Palms For Moderately Severe Cold Weather

(Palm Trees for Very Cold Weather – 16 to 23 degrees F. or warmer)

All plants from the previous list. 

Palms For Cold Weather with Predictable Freezes

(Temperatures 24 to 28 degrees F.)

In this bracket, you can grow all those palms in the previous two groups and a lot more.  Please note that this group is quite large.  All species that apply here will not be included, but I shall list many to give you some ideas of the nicest species possible. 

Palms For Minimum Temperatures Above 28 Degrees:

Count your blessings, for there are a lot more species you can grow.  Certainly, any of the above are for you, but you’re going to have some real fun because the list expands dramatically.

What To Do If You’ve Suffered Cold Damage

Here in Southern California, in 2007 we had one of the worst freezes in 60 years.  People have reported damage to palms that have been around for decades.  Farmers in some areas have lost the year’s crops.  It’s frustrating for all of us.  But, there’s an optimistic side to all of this.  Except in the hardest hit areas, most palms came back.  Some were lost.  This once again emphasizes the basics when you plant palms.  Be realistic in picking the right species.  Uninformed purchases from large depot type stores without proper guidance may result in losses.  Plants grown in warmer areas outside of your area and then market to you might not withstand your cold weather.  To avoid these problem, support local nurseries near you and get their advice.   

If you have a palm that’s been damaged by cold, there are things to do and inspect to see what your plant’s future might be.  Everyone notices the discolored and browned leaves.  Burn can be a faint yellowish-brownish discoloration or, if severe, a dark chocolate-brown or black discoloration.  This may become more apparent as days or weeks proceed.  So, if you see this, how can you see if the plants going to make it?  You check for evidence that the palm is still growing.  Here’s how:

1.  Look at the new spear coming out of the crown.  Is it green and healthy looking? (good sign).  Is it a mixture of green and brown? (worrisome but better than totally brown).  Is it totally brown or black?  (very worrisome)  Is it mushy? (bad sign)  Does it pull out with a gentle tug? (bad sign)
2.  Is the crown of the palm below the spear firm and hard? (good sign)  Is it mushy or soft? (very bad sign).
3.  Is the trunk collapsing or showing vertical indentation lines?  (very bad sign).  Is the trunk leaning over or bending? (get the shovel out).
4.  Are some of the older leaves still green despite the spear looking bad?  (probably of no importance.  It’s the spear and new growth that count)
5.  Is the new growth spear emerging out of the crown? (most important good sign).  Measure this by holding an older leaf petiole right up next to the spear and with one stroke mark both horizontally with a magic marker.  This shows you where the spear is right now.   Then inspect it in a day or two to see if the spear is emerging or moving upwards.  If it is moving out, that shows promise.  It’s no guarantee the palm will live.  But, if after a few weeks there’s not a millimeter of movement, that’s not good.

There are exceptions.  Spears can pull out and occasionally the plant will live.  There can be spear growth and yet the plant goes on to die.  A plant can stall for some time and yet still recover.  But, these inspections above are indicators of what’s to come.  Remember to give prophylactic fungicides down the throat of the plant when you see cold damage.  Although no studies I’m aware of document it’s benefit, most growers advise this treatment.  Possible fungicides to use include copper based fungicides and another named Daconil ( Chlorothalonil ).  It might be marketed under different names, so ask for help when purchasing.  Always use protective gear when spraying pesticides.

Phil Bergman