How to Grow Hardy Palm Trees Outside in Zone 5,6, and 7
An unusually warm winter has revived my interest in northern tropical gardening. It is not news that overall, mean temperature gradients are increasing across the country. This may promote better results with semi-tropical gardening. It may come as a surprise to many that some gardeners experiment with palms and palm trees in their gardens in states such as New York, Ohio, and Illinois. In fact, palms and other semi-tropical plants grow with little or no protection with vigor in states such as Virginia despite cold winters, and gardeners that live in states with harsher winters just need to administer a little protection to cold hardy palms to keep them in the ground all year round.
Extensive protection of mature Montreal palms
- Plant palms if possible in the warmest micro-climate with a south exposure
- Wrap the leaves in burlap or similar landscape fabric
- Apply a copper-based fungicide during wet weather and in the early spring.
- Apply anti-desiccant to the leaves before severe cold spells
- Mulch the base and the crown of the plant a few inches
What to Expect (Realistically)
In my experience, the weather patterns that affect palms the most are wet, cold weather and, in my southern New York zone 6b location, about twice every winter we receive an ‘arctic blast’ with temperatures that dip into the single digits (°F) and don’t rise much higher for 24 hours. I’ve had plants that have done fine with temperatures in the range of 15-30° F only to succumb to these annual occurrences.
When plants survive these cold spells, they are typically defoliated completely (with my lenient protection), but they will produce leaves again in the spring if they have adequate growing conditions. Due to this, expect that the beautiful leaves on your newly planted palm will not be anywhere near as elegant the following year unless you use intensive protection. However, such an interesting garden specimen is worth it, in my opinion.
Methods for Optimum Success
Depending on the weather conditions your area experiences, semi-tropical plants may or may not need extensive protection, however protecting palms will provide the greatest chances of success, or preserve more plant tissue and possibly leaves if blessed with a mild winter. At minimum, palms should have a copper-based fungicide applied to the leaves, stem, and crown before and after wet conditions.
If the new growth of the palm ‘pulls’ out of the crown, the plant is in decline and will require a dousing with the fungicide in that area. The palm should also be treated with an anti-desiccant such as Wilt Pruf ™, which will help the plant hold water in freezing conditions. The key to aiding palms in the winter is to keep them as dry as possible (especially the crown, where damage can be fatal), and keep them desiccated. It would even be beneficial to water the plant with warm water after long periods of dry or freezing weather.
Protecting the palm with mulching can increase the temperature and prevent strong wind chills from affecting the leaves so severely. If your area is expected to have such prolonged low temperature drops (-5-15F), a make shift cage filled with dried leaves, straw, or other similar substrate is a good idea. The 'cage' will prevent the mulch from being blown away°. Surprisingly, snow acts as an insulator and is beneficial.
Cold hardy palms have had success reports all over the map, and some are very impressive sounding. This may be a decent guide to provide insight into a plant’s potential hardiness, but remember that what will really determine your plant’s success is its location near wind-barring structures, the duration of extremely cold temperatures, the amount of damaging ice (freezing rain) and the frequency of wet weather between periods of cold.
The Hardiest of the Hardy Palm Selections
The Needle Palm
Without a doubt, the needle palm and its many developed cultivars is the best choice for the beginner northern palm enthusiast or even for gardeners just looking to add an unusual specimen to the landscape. These plants are hardy enough to not require protection and could possibly emerge from a winter with little damage as well. Their drawback is that they grow very slowly and won’t really achieve visual interest until they mature over the course of several years. This is why I highly recommend purchasing mature specimens that have at least an inch or 2 of trunk, even if they are relatively expensive. Older plants also have the advantage of being hardier. I would protect the plant for the first winter if making the investment for the best results. These plants can be found on specialty websites and Ebay.
The Windmill Palm (trachycarpus fortunei)
Another popular choice, this palm and its cultivars (several other varieties have been introduced as even hardier) are known to be the hardiest palm trees in the world. Yes, an actual palm tree. Well, that word excited me. If the tree were to be a success in your Zone 5-7 garden it would never fail to impress and provide endless bragging rights for you. When purchased young, they make for attractive tropical-looking shrubs, but if you really wanted to take the plunge and buy a specimen so mature that it has developed a visible trunk, for most climates north of southern New Jersey there will be unfortunate damage to the tree that will be apparent during the summer. A possible exception may be a flawless micro-climate along with protection that would essentially add another zone of warmth and a shield against damaging arctic blast winds. Windmill palms in tree form may be for the intensive palm enthusiast who is willing to invest time and money in the endeavor, but they still have use as great looking understory shrubs for causal gardeners with their gorgeous palm palmate leaves that cannot be replicated with true north hardy plants.
The Saw Palmetto (Serenoa repens) and Sabal Minor
The Sabal Minor, also known as the dwarf palmetto, is actually native to the southeastern United States up to North Carolina. The saw palmetto may sound familiar from health stores, and is also a native to the more northern southern states. They are the palms that begin to dot the middle of the traffic islands on your road trips toward the Carolinas. Each are low lying palms in the north that have similar hardiness to the needle palm. A dense planting of young specimens host the ability to look exquisite and exotic in the northern garden with the right design.
The Pindo Palm (Butia capitata)
These pinnate leafed palms are exciting for being one of the very few tropical ‘palmy'-looking plant that is unmistakable. I haven’t had success with this plant, but I also lack adequate light in my shady garden. However, this plant more than likely requires all the aforementioned protection methods from a determined gardener. With success, the plant will return late spring re-growing a few elegant palm leaves that islands are famous for. Among an intelligently planned garden with other tropical-looking plants, it will make a dramatic statement. At almost any age, they are beautiful, yet larger plants yield better results.
There are many other palms that can be experimented with in the northern garden, and specialty plant shops are developing specially bred varieties for their ability to acclimate to the conditions of the northern states. The Chinese fan palm is a plant that, well not as hardy, can be cheaply purchased at stores such as Home Deopt and is worth a try. With more weird winters showing up such as the one we had in 2011, garden experimentation should be mandatory. Plant palms alongside other hardy tropical-looking plants to give people something to look at outside of the massive plantings of rhododendrons and forsythia bushes.