Protecting palm trees and other exotics from frost

When should you protect your palm trees or other exotic plants against frost? We are often asked this question and there is not always an unambiguous answer. Take heed of the combination of wind and frost. A plant prefers a crystal-clear night with -12 dan two days of -8 in combination with an eastern wind with wind force 6, The chill temperature (the ‘felt temperature’) would drop much lower. Because of icy winds, plants can also damage due to droughts. If we would get dry lips due to the cold weather, expect plants to suffer as well. 

Tree ferns can dry out completely due to frost. Most people think the plant cannot handle the cold, but the drought caused by the cold is much more dangerous, especially with eastern winds. 

In short: the reason why we conservatively say protect from … instead of hardy until a certain temperature is due to the fact that a minimum temperature does not say as much. Additional aspects play a role as well, such as: 

• Is there a thick layer of snow? (Could work isolating for the soil, but that does not apply when the snow is located on top of the leaves.) 
• Does the temperature drop early in morning to a far minimum with sun during noon or is it that temperature for many nights without sun during the day with temperatures around 0 degrees? 
• Is the cold combined with dry (eastern) winds or is there no wind at all? 
• Given temperatures on our site are meant for plants in full soil. A potten palm or plant is more vulnerable, as a pot can freeze completely. During a frost of -10 for two days long, this frost creeps into the soil for about 10-15 cm deep; this could still mean the roots are left unharmed. This is different in a pot. 

Surprise effect: 

For years, I have had to point out to customers that certains plants are not winter hardy and that is is better to keep them as a potted plant. I often receive the reply ‘Ah, but we do not get these low temperatures anymore’. You only need 1-2 nights of a cold snap to damage your beautiful plants if they are not protected. As we have not had cold winters for the last few years, I expect many people to be taken by surprise. Preventing is better than curing, so to help you out with your plants, you can find a few useful tops below. That way, you will be more prepared. Some plants are too beautiful to neglect, so make sure to give them the extra effort. 

Bananas: 

With for example Musa basjoo and Musa sikkimensis, the trunk will often stop growing at -5; instead, they will continue from below (if no protection is used). Some people put a pipe or something similar around the trunk and add hay to protect it, but if temperatures drop to -10, they will not continue growing from the trunk (and instead, grow from below as well). It is very important to use old leaves (prefered oak), wood chips, old blankets, pine branches or anything similar, to protect around the area around the trunk. That way, you will protect the underground rhizome against frost, so it can continue to grow in spring. Bear the tips for potted plants above in mind if you have a potted banana. 

Tree ferns: 

Dicksonia antarctica and Cyathea australis can handle quite some frost. The leaves will turn brown at -4/-5. Cut these off at around 20 cm from the trunk. The vulnerable part of a tree fern is the crown. Put as much hay or leaves as possible in the crown to protect it. Proceed with wrapping climate cloth or old blankets around it. Finish it off with bubble wrap and tape; do not forget to surround the bottom of the trunk for another 30 cm to protect the roots. This is only possible with tree ferns. Never use plastic or similar non-breathing materials with palms.

Palm trees: 

Try relocating palms in a pot to a sheltered location. Put them closely together and make sure to protect the pots a swell. A frozen pot with a palm/plant in full (eastern) wind will quickly dry out your plants as the roots cannot continue their sap stream. 

It is recommended to apply some mulch around the trunk. Many people in colder areas use our root protection as well. 

It is important to bind the leaves together. The most vulnerable part of a palm tree is the spear. Do not just protect the leaves but also the top of the trunk (around the spear). You can use winter protection, climate cloth, a reed mat or similar around it and to finish it off with a blanket around the whole.

Olive trees:

Olive trees are often potted; try to relocate the tree to a sheltered location and protect the pot. To protect the leaves, you can apply winter protection, climate cloth or warm blankets. It is especially important to protect the leaves if it is windy.

I hope, without inducing fear, that I have been able to contribute to a solution against the cold that is setting in quickly.