Manage Cold Hardy Palm Trees

A cold hardy palm tree is determined by many factors, three of which are discussed in this article: The way the palm acclimates or responds to the cold weather. The mid-winter hardiness of the palm. And lastly, the way the palm de-acclimates when the weather starts to warm up. The acclimation process is activated as the temperature starts to decrease. These environmental changes trigger physiological and biochemical changes in the palm tree that result in greater cold tolerance. After the acclimation process the palm tree will be in a stage of mid-winter hardiness, where it has reached its maximum hardiness level with out injury. Lastly the De-acclimation process is exactly the opposite of the acclimating process. It refers to the response to warming temperatures in late winter and early spring.

The solution to the success of a cold hardy palm or tropical palm relies on many factors, some of which are: the overall health of the palm tree, the maturity, when it was transplanted, how long has it been stationary, the environment in which it has been grown in, and the species of palm.

Overall Health
The overall health of palm trees plays an important role on how well the palm will survive. A much healthier palm is proven to survive with minimal damages to the fronds and trunk. Making sure the palm has adequate nutrients in the soil is key for the well being of the palm. Studies show that adding fertilizer and other nutrients during winter will have no affect on the survival of the palm tree. When the palm tree starts the acclimation phase, it will start to enter a phase of hibernation. Biochemical changes occur, photosynthesis process decreases, therefore, less sunlight is needed and less nutrients is required. The palm tree stops absorbing nutrients and stores the nutrients it previously absorbed in late summer, early fall. Thus, making it very important to keep a healthy palm tree, all year round. However, there are preventative measures that may ensure the survival of your cold hardy or tropical palm; please refer to our winter protection article.
One solution is to fertilize your palm in mid-summer. This will to help the palm tree during the de-acclimation phase as well as during winter months. This will give the palm tree ample time to gather the nutrients provided and boost their health as winter arrives and will also provide the nutrients it will need to start its growth when spring comes.

The Maturity of The Palm
The maturity of the palm is also another key factor in determining the survival of the palm. When an immature palm tree is introduced to cold weather the chances of survival with out damage is much less of that of a mature palm tree. A mature palm will have extra leaves to give off heat to protect the inner bud or the new arising spear. This spear is more or less the life line of any palm tree.
A mature palms will also have more of an extensive root system which will allow the palm tree to recover faster by absorbing the water and other nutrients needed when damaged. As for an immature root system, the roots may freeze or may not tolerate cold weather and start to rot or decay.
The maturity of the trunk can also help with the protection of the palm tree. Some cold hardy palms have developed a husk to protect the trunk from frost or other unseen events given them an advantage when the natural elements come forth. The husk acts as an outer layer of protection, some examples of palms that have a outer fiber husk are the European Fan Palm (Chamaerops humilis), Windmill Palm (Trachycarpus fortunei), Miniature Chusan Palm (Trachycarpus wagnerianus), Stone Gate Palm (Trachycarpus princeps), and other related species of the Trachycarpus family. Some examples of cold hardy palms with out the fiber husk are the Bismarck Palm (Bismarckia nobilis), Cabbage Palm (Sabal palmetto), Blue Hesper Palm Tree (Brahea armata), Needle Palm (Rhapidophyllum hystrix) and the Pindo Palm (Butia Capitata). Many of these palm trees can with stand freezing temperatures for days or even weeks with out any damage.
One solution to assist in the survival of a palm tree during the duration of cold months, is to only plant mature palm trees outside and keep the little ones indoors and inside containers. Once, the weather starts to warm up in spring and the palm tree is mature, than transplant outside. You can refer to our transplanting article.

When The Palm Was Planted?
When the palm tree was planted is important, because this will indicate how long the palm had to establish its root system. If the palm tree was planted close to winter, this might lower the chances of survival because sufficient time was not given for the palm tree to pass the transplant shock and to establish its roots. All palm trees go through a transplant shock, some for a few days and some for a month or two. Deciding to plant around winter could prove to be a challenge.
One solution to planting a palm tree, is to plant it during spring or when the weather is warming up. For other tips and preventative measure please refer to our winter protection article.

How Long The Palm Has Been Stationary?
How long the palm has been stationary plays an important role in the palm trees survival. The time the palm tree is planted in a specific area without being disturbed is critical, not only to cold hardy palms, but to plants in general. Cold hardy palms, as well as tropical palms, also have a high tendency to die slowly, because they were transplanted to many times. Palm trees in general, do well when they are transplanted once; from a container to the ground. When a palm tree has been stationary for a long period of time, their root system will be more extensive. This will help during times of drought, cold, or lack of nutrition in the surrounding soil. By having more time to settle, the palm tree can be ready for winter season.
One solution is, once the palm is safely transplanted in the ground, the palm tree must not be disturbed for at least 2 to 3 years. During these years the location of the palm should not be relocated for any reason. This is the rule of thumb for most palm species, including cold hardy palms.

The Environment The Palm Has Been Grown in
The environment the palm tree has been grown in, is some times overlooked by many people. Many commercial growers will have hundreds if not thousands of palm trees growing all different species at one time. Most in green houses and some outside in fields. Most of which are in the south, where weather will hardly ever reach below freezing. A palm tree that has never experienced weather of its natural habitat will be affected by the cold more so than a palm that has been winterized or has been growing in their natural habitat. Winterizing is another word for acclimating palm trees.
Some nurseries will acclimate the palm before selling them to northern customers to ensure their survival when the harsh winters arrive. Some nurseries will refer to this as either, winterizing a palm or acclimating a palm. The reason for choosing palm trees which have been acclimated to the weather is because the palm trees will better resist cold temperatures. Many palm trees even cold hardy palm trees when introduced to the cold weather will go into a state of shock because it is not adapted. This process may also be done first hand. It is not necessary to do this, but the reward is much greater. This is especially true if it is during the coldest part of the year. Do not test the limitations of the palm, acclimate it slowly into the cold or full sun.
The altitude of the environment the palm tree is grown is just one more environmental factor which influences cold hardy palms. For instance, queen palm trees are found growing naturally throughout Florida which is completely flat and of low altitude levels. But, they are also found growing naturally throughout South America, which consist of many altitude variances with many lusciuos and colorful landscapes; unforgiving mountains, monster rivers, wet swamps, and many more of mother nature's lab experiments. Some, queen palms which grow in these regions are considered to be coldly hardy, and winterized by mother nature with her harsh climates consisting of gail winds, fat hail, merciless snow, and many more natural occurrences.
The safe and stable solution to winterizing a palm tree, is to winterize only palm trees which have already stood the test of time with mother nature, i.e. cold hardy palms. You don't want to winterize a Fiji Fan Palm, because it would take many decades, if not centuries to shape the biological structure. It's also, important to note that hybrids made of cold hardy and tropical flavors, have successfully endured cold months and have been winterized, but the results all vary with each species. So, mixing species is not a stable solution, but nevertheless it is stilled considered a solution.

The Species of Palm
The species of palm is the most important in determining the cold hardiness of a palm. Over the years many palm tree botanist and palm tree enthusiasts have studied the hardiness of many plants and palms. The hardiness of palm trees is due to hundreds, thousands even millions of years of the same natural reoccurring weather. This is called their natural habitat. The natural habitat of a palm will usually indicate the lowest temperature the palm tree can withstand. Every species of palm has a country of origin or a location where they grow naturally with out human intervention. Those thousands and millions of years have let certain species adapt to their environment. Some examples are a European Fan Palm (Chamaerops humilis) from the cold chilly Mediterranean, Windmill Palm (Trachycarpus fortunei) from the foot hills of the Himalayas, and the Blue Hesper Palm (Brahea armata) from the desert canyons of northwestern Mexico. These species of palm tree will inevitably be more cold tolerant than those of such places as Fiji, Philippines, or the Amazon.
To compare locality of a palm to its cold hardiness, is as follows A European Fan Palm (Chamaerops humilis) native to the Mediterranean is more of cold hardy palm then to a Canary Island Date Palm (Phoenix canariensis) from the Canary Islands. As a Needle Palm (Rhapidophyllum Hystrix) from Central United States is more cold hardy then to a European Fan Palm. Studies have indicated leaf damage to the European Fan Palm at temperatures below that of 13 degrees F, on the other hand, the Needle Palm have shown little to no damage at temperatures of 5 degrees F and below.
This is why it is most important when choosing a palm, to not only look at the zone temperature it may be tolerant, but also the minimum temperature it can tolerate and also it's natural habitat.

Summary
A cold hardy palm tree is determined by many factors, three of which factors are: The way the palm acclimates or responds to the cold weather. The mid-winter hardiness of the palm and the way the palm de-acclimates when the weather starts to warm up. Which is also contingent on the following: the over all health of the palm tree, the maturity, when it was transplanted, how long has it been stationary, the environment in which it has been grown in and most importantly the species of palm tree.