Hardy palms

Hardy palms are any of the species of palm (Arecaceae) that are able to withstand colder temperatures and thrive in places not typically considered in the natural range for palms. Several are native to higher elevations in Asia and can tolerate hard freezes with little or no damage. Many of these species can be cultivated at high latitudes, and in places that regularly see snow in winter.

The hardiest species are found in the genera "Rhapidophyllum", "Sabal", and "Trachycarpus". Members of these and other genera are sometimes grown in areas where they are not truly hardy, overwintering with the aid of various kinds of artificial protection.

The minimum temperature a palm can sustain depends on a variety of factors, such as humidity, size and age of the palm, daytime high temperatures, or the length of time the temperature is at the minimum. -5 for several days will do far more damage to a palm than an overnight low of say -8 for an hour or so.

Fan palms

The fan palms (Arecaceae tribe Corypheae; palms with fan-shaped leaves) include all of the hardiest palms.
*"Trachycarpus" palms ("Trachycarpus fortunei, T. takil") - the best known cold-hardy palms, these tough species are native to the Himalaya and east to central China, where although not growing so far north (to about 31°N) as the Needle Palm, they do grow at high altitudes where temperatures are cool. The Chusan Palm ("T. fortunei") is hardy to −27.5 °C, survived by four specimens planted in Plovdiv, Bulgaria during a severe cold spell on 6 January 1993. It is also tolerant of low summer temperatures (15 °C) in oceanic climates. This enables it to be cultivated further north than any other palm, with mature trees successful as far north as 58°N in northern Scotland. Mature specimens can also be found in most parts of England, the Vancouver region of Canada, around Tokyo in Japan, and Tasmania, Australia. "Trachycarpus fortunei" is also being grown experimentally in Tórshavn on the Faroe Islands (62°N), with young plants growing well so far (Højgaard et al., 1989). A tree of "T. fortunei" has been growing at the Brooklyn Botanic Garden in New York City since the 1980s, albeit protected by a plastic wrap during the coldest months.
*Mediterranean Fan Palm ("Chamaerops humilis") - The only palm native to southern Europe, and very drought-tolerant. Hardy to −12 °C, but does prefer hot summers. Despite the fact that this palm is less hardy than many palms listed here, it has the northernmost native habitat because of the mild Mediterranean climate. It is found in abundance across most of southwestern Europe and northwestern Africa. It is a very slow-growing plant.
*Needle Palm ("Rhapidophyllum hystrix") - This clustering and usually trunkless palm is native north to South Carolina in the United States. It is considered hardy to USDA zone 6 and can be cultivated without protection as far north as the New York City metro area, including the Hudson Valley and Connecticut. With some protection, it is possible to grow one to the north in New England. They have proven hardy in the Tennessee valley region and up into the Ohio Valley and Mid-West areas with hot summers. During the winter, it can tolerate temperatures as low as −23 °C. The needle palm is very slow growing and rarely reaches heights of over 1 metre. There are documented specimens that have been growing in White County, Tennessee, since the early part of the 1960s that are at 3 m in height.
*Mazari Palm ("Nannorrhops richtiana") - This palm, native to the dry, mountainous terrains of Afghanistan and surrounding regions, is also thought to be extremely cold hardy (perhaps to about −20 °C), though also requiring hot summers and dry soils. However, due to its limited availability in cultivation, not much is known about this palm. Mazari Palm is not easy to grow, perfect drainage and full sun are required for this palm to survive. This palm will not tolerate wet freezes.
*Saw Palmetto ("Serenoa repens") - Native to Florida, this bushy palm is hardy to about −15 °C. This bushy palm grows in abundance within wetlands and subtropical grasslands of central and northern Florida. Extract from Saw Palmetto is often used to treat problems with the prostate.
*"Sabal" palms (palmettos; 13 species) - These palms are native to the southeastern United States, Central America, and the Caribbean. The Dwarf Palmetto ("S. minor") is the hardiest species in the genus. The cultivar 'McCurtain' is considered the hardiest, to USDA zone 6, like the needle palm. It can tolerate short periods of temperatures as low as −22 °C. A southern Arkansas cultivar may be just as hardy and grows larger than the McCurtain palm.One of the possible reasons that the dwarf palmetto is so hardy is that it forms a trunk, and in the coldest of climates grows very slowly, rarely producing much of a noticeable trunk (but in warmer climates can attain up to 3 m of above-ground trunk). The Cabbage Palmetto ("Sabal palmetto"), the state tree of both Florida and South Carolina, is very common on the southeast coast of the United States. The species is considered hardy to USDA zone 8, and may survive short periods of temperatures as low as −14 °C. A number of Cabbage Palmettos grows in the North Atlanta area (zone 7a). The Mexican Palmetto ("Sabal mexicana") is a close relative of the Cabbage Palmetto, native to southern Texas and northern Mexico. It looks like a more robust version of the Cabbage Palmetto, with a larger trunk, although they may be difficult to tell apart. Cold hardy to about −9 °C, and grown throughout Texas in cities such as San Antonio, Austin, and even Dallas. Another trunking Sabal worth to try in Zone 8a and warmer is Sabal uresana, its cold hardiness is similar to Sabal palmetto. Typical Sabal uresana has blue fronds although a green leafed form exists and is supposedly even more cold hardy.
*"Trithrinax campestris" - It is native from northern Argentina, from lowlands to the mountains of Sierras de Córdoba and Sierras de San Luis, trees growing at altitudes withstand teperatures at least −15 °C.
*"Washingtonia" palms ("Washingtonia filifera, W. robusta") - These palms are native to southern California and northwest Mexico, growing as high as 30 m in their native habitat. California Washingtonia ("W. filifera") is hardy to −12 °C; it prefers a dry Mediterranean climate, and will not grow taller than 12-15 m in a humid area. It is sometimes grown in containers or planted as short-term specimens in areas where it is not hardy. Mexican Washingtonia ("W. robusta") is somewhat less hardy, native to northern Mexico and southernmost California. It has a more robust trunk and stiffer leaves than "W. filifera", and is hardy to −10 °C. It has been grown in Houston, Texas and New Orleans, Louisiana. Washingtonia robusta, even though somewhat less hardy, may be a better choice for US South-East because it is more tolerant of high humidity.
*"Rhapis excelsa" is hardy to about −7 °C.

Pinnate-leaved palms

Few palms with pinnate leaves tolerate much frost. They belong to several tribes of the Arecaceae, with the species listed here belonging to Tribe Areceae ("Chamaedorea"), Tribe Cocoeae ("Butia, Jubaea") and Tribe Phoeniceae ("Phoenix").
*Chilean Wine Palm ("Jubaea chilensis") - A contender for the hardiest pinnate-leaved palm, it is hardy to about −12 °C and has been cultivated successfully as far north as London in England. This palm does not perform well in hot, humid climates but has proven hardier than "Butia capitata" in cooler, maritime climates in such places as Great Britain and the Pacific Northwest. Chilean Wine palms have a very small native range, grow very slowly, and thus it is exceptionally rare to find fully grown examples outside of Chile.
*Butia Palm or Feathery Palm ("Butia capitata") - With "Jubaea", possibly the hardiest known pinnate-leaved palm. It is also hardy to −12 °C, and has been experimentally cultivated in Delaware and Washington. It thrives in humid subtropical climates. This tree is commonly known as the "jelly palm" because of the sticky, edible fruit it produces, which is used in many South American countries as jelly.
*"Chamaedorea microspadix" and "Chamaedorea radicalis" are the hardiest known species in the genus "Chamaedorea". Both species come from Mexico and are considered stem hardy to about −11 °C, although they will lose their leaves at temperatures below about −6 °C.
*Canary Island Date Palm ("Phoenix canariensis") - This species is hardy to about −8 °C, [ [http://www.hardytropicals.co.uk/Palms/Phoenix_carnariensis.php Phoenix caneriensis, hardy to about −8 °C] ] and is grown as far north as the south of England (50°N), producing viable seed. This palm is one of the most commonly grown palms in the world. Well adapted to low humidity and little watering, this palm is used as an ornamental in both Mediterranean climates and desert climates. In more humid climates, these trees will often be seen with sword ferns sprouting just beneath the crown.
*Cretan Date Palm ("Phoenix theophrastii") - Another species of "Phoenix" which may show similar frost tolerance, native to Crete and southwest Turkey, but has not been adequately tested.
*Date Palm ("Phoenix dactylifera") - This relative of the Canary Island date palm, and producer of the edible date, is also hardy to about −10 °C, but does not tolerate very wet areas. This palm is one of the staple plants of the Middle East for its versatility and edible fruit.
*Queen Palm ("Syagrus romanzoffiana") - Hardy to about −8 °C. Probably the most tropical, exotic looking palm for subtropical areas, this palm is native to central and eastern South America. Formerly named "Cocos plumosa", it has graceful, flowing plumose fronds. Very fast growing and invasive, this palm is often treated as a weed in much of Florida.
*Mule Palm ("XButyagrus") - Hardy to about -10 °C (14 °F). Man made hybrid between the Butia palm and Queen palm. One of the hardiest feather palms. Combines the hardiness of the Butia palm with the fast growing, tropical fronds of the queen palm. Mature specimens are quite rare due to the difficulty in producing this palm.

Hardy Palm Monikers

Some plants used in “hardy subtropical” landscaping that are commonly referred to as “palms”, but truly are not in the Arecaceae family, include the following:
musa basjoo banana, yucca, canna, sago palm, hardy types of bamboo, and occasionally the sumac Rhus typhina. This is not an all inclusive list and is subjective.

They Really Are Hardy!

With protection, some of the more hardy species may be kept in USDA zone four. Great candidates for this are trachycarpus fortunei (Windmill Palm), rhapidophyllum hystrix (Needle Palm), and sabal minor (Dwarf Palmetto). Palms can be protected by having a temporary greenhouse erected around them, being wrapped in burlap, or even being kept inside a box and warmed with lights. Do not be afraid to experiment and try to keep cold hardy palms in your area, even if your area is cold. With good protection, a palm can survive in a much colder environment than it could without any at all.

References and external links

*Højgaard, A., Jóhansen, J., & Ødum, S. (1989). A century of tree planting on the Faroe Islands. "Ann. Soc. Sci. Faeroensis" Supplementum 14.
* [http://www.hardytropicals.co.uk/Palms/Phoenix_Canariensis_at_Southsea.php "Southsea Island" Date Palm] (Information about the Canary Island Date Palms in Southsea producing viable seed)
* [http://www.polarpalm.net/ Polar palms] (documents cold tolerance of "Trachycarpus" in Bulgaria)
* [http://www.trebrown.com/documents/climate/palmhardinesstrials.php Temperature tolerances of some palms]
* [http://www.scanpalm.no/english.html Scanpalm - everything about palms in Scandinavia] , about the palms that grow, or should be tested, in Scandinavia.
*Palm hardiness research in the Greater Cincinnati area: [http://www.cas.muohio.edu/coldhardypalms/index.html Cincinnati area hardy palm research]
*Cold-Hardy palms in Southwest Ohio: [http://www.palms.org/palmsjournal/2002/ohio.htm]
* [http://members3.boardhost.com/MIDWESTPALMS/ HARDY PALMS IN TEMPERATE ZONES FORUM]
* [http://members3.boardhost.com/HardyPalm/ HARDY PALM AND SUBTROPICAL BOARD]
* [http://forums.gardenweb.com/forums/palms/ PALMS AND CYCADS FORUM]
* [http://members3.boardhost.com/joe02917/ HARDY PALMS AND MORE FOR THE NORTHEAST]