The Washington Palm is endemic to the deserts of Mexico and is also known as the Mexican Fan Palm or, sometimes, petticoat palm. It belongs to the tribe Corypheae, subfamily Coryphoideae, genus Washingtonia and species robusta. The Washingtonia robusta is fast-growing, hardy, and tall. In the wild, it is found near permanent surface or subsurface water. It has been widely used in years gone by as a street palm.
It is a ‘solitary’ palm meaning it has a single trunk. It can grow to well over 20 metres under the right conditions and has a spread of 3 to 5 metres. It adapts to a wide variety of soil types and has a high drought tolerance. It also has a moderate tolerance to salt spray and, once established, will withstand occasional periods of below-freezing temperatures.
The canopy consists of 30-odd bright green, fan shaped or palmate leaves about a metre long with ribbed, drooping segments. On juvenile plants, there are white threads between the segments. The inflorescence is 2 to 3 metres long and appears from amid the leaf bases. The white flowers open in summer and turn into brownish-black, fleshy fruits.
Although the Washington palm is a striking specimen of great height, it does come with a few drawbacks.
* it is not self-cleaning and, if not kept tidy, dead fronds generate a shaggy, dense covering which is then likely to give shelter to rats and other rodents as well as becoming a fire hazard
* the leaf stalks or petioles are very spiny and this, added to the height of the tree, makes removal of the fronds hazardous in the extreme
* the palm’s height makes it susceptible to lightning strikes. A lightning strike usually means the death of the tree.
Although a dramatic and striking tree, its habit of having all the canopy at the very top of a very long, slender trunk makes it appear out-of-scale unless planted among multi-storied buildings. It will have a thicker trunk, grow more slowly and not as tall if it has some restrictions placed on its water intake eg being planted in unirrigated areas. It needs full sun but juvenile trees will cope with some shade. It should be transplanted with a large root ball if the transplant is to be successful. Although tolerant of a variety of soil types, most palms prefer a pH between 5.0 and 5.5 so if planting a new palm, try to reach this ideal pH so you give your new plant every chance of a successful start in life. Low pH can be improved by adding lime to the soil. Peat moss can be added if the pH is above 5.5.
The Washington palm is certainly an eye-catching example of its tribe and makes a stunning specimen tree.