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Publication #ENH-827

Washingtonia robusta: Washington Palm1

Edward F. Gilman and Dennis G. Watson2

Introduction

Commonly seen at 40 to 50 feet but capable of soaring to 80 feet in height, Washington Palm is quickly recognized as the much-used, straight, single-trunked street palm of years past. The lower leaves persist on the tree after they die, forming a dense, brown, shaggy covering below the living, bright green, broad, fan-shaped leaves, giving it the common name of petticoat palm. These dead fronds are known to be a fire hazard and a popular bedding roost for rodents and, because of this, must be removed by law in some areas. The sharply barbed leaf petioles and tall, thin trunks make frond removal a rather unpleasant task, but some people think the rapid growth rate and statuesque appearance more than make up for this trouble.

Figure 1. 

Middle-aged Washingtonia robusta: Washington Palm

General Information

Scientific name: Washingtonia robusta
Pronunciation: wosh-ing-TOE-nee-uh roe-BUS-tuh
Common name(s): Washington Palm, Mexican Washington Palm
Family: Arecaceae
USDA hardiness zones: 9A through 11 (Fig. 2)
Origin: not native to North America
Invasive potential: According to the IFAS Assessment of the Status of Non-Native Plants in Florida's Natural Areas (Fox et al. 2005), Washingtonia robusta (Washington palm) may be used with caution in southern Florida1, but should be managed to prevent its escape (counties are listed by zone at: http://plants.ifas.ufl.edu/assessment ); and is not considered a problem species and may be used in the northern and central zones of Florida.
1Current assessment is incomplete; please check for updated information at: http://plants.ifas.ufl.edu/assessment
Uses: street without sidewalk; specimen; sidewalk cutout (tree pit); tree lawn 3-4 feet wide; tree lawn 4-6 feet wide; tree lawn > 6 ft wide
Availability: not native to North America

Figure 2. 

Range

Description

Height: 60 to 90 feet
Spread: 10 to 15 feet
Crown uniformity: symmetrical
Crown shape: palm, upright/erect
Crown density: open
Growth rate: moderate
Texture: coarse

Foliage

Leaf arrangement: alternate (Fig. 3)
Leaf type: costapalmate
Leaf margin: entire
Leaf shape: star-shaped
Leaf venation: palmate
Leaf type and persistence: broadleaf evergreen, evergreen
Leaf blade length: more than 36 inches
Leaf color: green
Fall color: no color change
Fall characteristic: not showy

Flower

Flower color: white/cream/gray
Flower characteristics: showy

Fruit

Fruit shape: oval, round
Fruit length: less than .5 inch
Fruit covering: fleshy
Fruit color: black
Fruit characteristics: does not attract wildlife; not showy; fruit/leaves not a litter problem

Trunk and Branches

Trunk/bark/branches: branches don't droop; not showy; typically one trunk; thorns
Pruning requirement: little required
Breakage: resistant
Current year twig color: not applicable
Current year twig thickness:
Wood specific gravity: unknown

Culture

Light requirement: full sun, partial sun or partial shade
Soil tolerances: clay; sand; loam; alkaline; acidic; occasionally wet; well-drained
Drought tolerance: high
Aerosol salt tolerance: high

Other

Roots: not a problem
Winter interest: no
Outstanding tree: no
Ozone sensitivity: unknown
Verticillium wilt susceptibility: resistant

Pest resistance: resistant to pests/diseases

Use and Management

Washington Palm makes a dramatic statement in the large landscape and creates a striking accent for multi-storied homes but often grows out of scale in most landscapes with one-story buildings because all of the fronds are at the top of the palm. It looks like a telephone pole with a green hat. Washingtonia filifera is a much better choice in unirrigated landscapes, since it grows more slowly, is shorter, and the trunk is thicker.

Washington Palm needs full sun for best growth but will endure some shade while young. It will tolerate poor soil and drought, and is hardy to about 20-degrees F. Transplant with a large root ball to ensure survival.

Washingtonia filifera is shorter, has a thicker trunk, and is better suited for planting in dry urban landscapes, such as in Texas. They reportedly suffer and often die from root rot when irrigated. Select Washingtonia robusta in an irrigated landscape and for the eastern U.S.

Propagation is by seed.

Pests

Coconut mealybug, palm leaf skeletonizer, palm platid planthopper and a variety of scales infest this palm.

Diseases

Root rot can occur if this palm is planted on a wet site.

Footnotes

1.

This document is ENH-827, one of a series of the Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date November 1993. Revised April 2007. Visit the EDIS Web Site at http://edis.ifas.ufl.edu.

2.

Edward F. Gilman, professor, Environmental Horticulture Department; Dennis G. Watson, associate professor, Agricultural Engineering Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer-Chancy, Interim Dean.