Last of our series on cold hardy palm trees is a discussion of 3 monotypic genres and a polytypic genre.
Jubaea Jubaea is another monotypic genus of palm, it is native to a small area of low forests and adjacent savannas in central Chile at the base of the Andes. Jubaea is like most plants in Chile in that it detests hot and humid weather.
Jubaea chilensis (Chilean Wine Palm) I admit I had no luck growing this wonderful giant feather palm, but I must mention the amazing specimen in Rock Hill, SC, planted in 1993 by palm harvester Tamar Myers. Although Jubaea chilensis can grow up to 80 ‘tall, with 3’ wide trunks in more hospitable locations, don’t expect that size in a temperate climate … if you can keep it alive. (Hardiness zone 8-10)
Serenoa Serenoa is another monotypic genus of palm trees native to the southeastern U.S., named for Serenoa Watson, a 19th-century Harvard herbarium curator.
Serenoa repens (Saw Palmetto) This native Gulf Coast palm is a vigorously grouping and spreading palm tree, often with logs underground and above ground. Serenoa repens can be easily identified by its spiny leaf petioles. The leaf color is usually bright green, but silver-gray forms can be found in certain populations. Serenoa repens is incredibly drought tolerant, but can tolerate flooded soils, can grow in sun or shade, and can thrive in sandy soils that are both acidic and alkaline … that’s a hardy palm. Try as I might, I was never able to make this survive the winters in our Raleigh garden (Hardiness Zone 8b-10)
Trithrinax (Spiny Fiber Palm) This South American genus of palm trees encompasses only three species, Trithrinax brasiliensis, Trithrinax campestris, and Trithrinax schizophylla. These beautiful trunk and cluster palm trees are found in grasslands and savannas in Argentina, Brazil, and only in the surrounding countries.
Trithrinax campestris (Argentine Silver Palm) I will never forget the day I first saw these palm trees growing in open savannas in northern Argentina in 2002 … without a doubt the most beautiful palms I had ever seen. Slow growing trunks eventually reach 12 ‘tall, clad in very stiff leaves that range from gray to the most beautiful silver gray you can imagine. I hope they show very good cold tolerance, but the key to winter survival in colder areas is to keep the plants dry as they are native to arid and desert regions. So far, I have killed my first two. (Hardiness zone 8b-10, guessing)
Washingtonia (Washington Fan Palm) Washingtonia is a genus of just two very tall, stemmed, fast-growing species named after who else, George Washington. Washingtonia filifera is native to the southwestern United States and Washingtonia robusta south of the Mexican border. While Washingtons can withstand some cold, they do much better in dry cold than in humid winter climates.
Washingtonia filifera ‘Dallas’ (Dallas Desert Fan Palm) We are pleased to offer a limited number of Washingtonia filifera native to the Southwest that was grown from seeds collected from a mature specimen in Zone 8, Dallas, Texas. The plant was “discovered” by Matthew Nichols of Dallas, who tells me that it has withstood 11 degrees F without damage. Hopefully this can add a bit more stamina as it has grown to fruiting size in a Zone 8 climate. Adult size is 60 ‘tall. (Endurance zone 8-10, guessing)
Washingtonia filifera ‘Truth or Consequences’ (Truth or Consequences Desert Fan Palm) The seed of this cold hardy form of the native of the southwestern United States (California, Arizona), Washingtonia filifera, comes from a plantation in Truth or Consequences, Nuevo Mexico, where it has reportedly endured 0 degrees F on several occasions. The cold in New Mexico is obviously a dry cold, and the east coast cold is much wetter, but the potential is exciting for gardeners who like to experiment. Mature plants reach 60 feet tall with leaves 8 inches wide. (Hardiness zone 8b-10, guessing)
Washingtonia robusta ‘Mariana’ (Mariana Mexican Fan Palm) This form was grown from the seeds of palm guru Hayes Jackson of Anniston, Alabama. Hayes obtained these seeds from a Washingtonia robusta plant (usually the least resistant Washingtonia), native to northern Mexico, which grows in the city of Mariana, in zone 8a of Florida. (Resistance zone 9-10)
Washingtonia x filibusta (Border Crossing Fan Palm) These hybrids between the Mexican fan palm, Washingtonia robusta, and the native US Washingtonia filifera were a blatant attempt to gain US citizenship and thus access to federal social programs for their offspring. These fast-growing hybrids are particularly happy in California and Texas, but have been successfully grown in other temperate parts of the country. If you are feeling particularly generous and want to adopt one of these descendants, don’t wait, as their number is limited due to the impending border fence. There was a splendid specimen of Washingtonia x filibusta in the Atlanta Botanical Garden for years until it was killed in a severe winter. Even the best cold hardy palm trees they have their limits.