Washingtonia filifera: Desert Palm

Introduction

Commonly seen at 40 to 50 feet but capable of soaring to 80 feet in height, desert fan palm is quickly recognized as related to the much-overused, straight, single-trunked street palm of years past, Washingtonia robusta. However, desert fan palm is better suited to the home landscape since it grows more slowly and is shorter. This also allows it to be used in more garden applications, such as containers or grouped together as a mass planting. It does not grow well when it is over-irrigated in Florida because it frequently develops trunk or root rot.

General Information

Scientific name: Washingtonia filifera

Pronunciation: wosh-ing-TOE-nee-uh fill-LIFF-er-uh

Common name(s): Desert palm, California washingtonia palm

Family: Arecaceae

USDA hardiness zones: 9A through 11 (Figure 2)

Origin: not native to North America

Invasive potential: not assessed/incomplete assessment

Uses: street without sidewalk; tree lawn 3-4 feet wide; tree lawn 4-6 feet wide; tree lawn > 6 ft wide

Description

Height: 40 to 60 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 (Figure 3)

Leaf type: costapalmate

Leaf margin: entire

Leaf shape: star-shaped

Leaf venation: palmate

Leaf type and persistence: evergreen, broadleaf evergreen

Leaf blade length: more than 36 inches

Leaf color: green

Fall color: no color change

Fall characteristic: not showy

Flower

Flower color: yellow, white/cream/gray (Figure 3)

Flower characteristics: not showy

Fruit

Fruit shape: oval, round

Fruit length: less than 0.5 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: needed for strong structure

Breakage: resistant

Current year twig color: not applicable

Current year twig thickness:

Wood specific gravity: unknown

Culture

Light requirement: full sun

Soil tolerances: clay; sand; loam; acidic; alkaline; well-drained

Drought tolerance: high

Aerosol salt tolerance: moderate

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

The lower leaves persist on the tree after they die, forming a dense, brown, shaggy covering below the living, grey/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.

Plant this palm only on soil which is extremely well-drained to prevent trunk or root rot. Moderate salt tolerance allows it to be used close to the coast in several of the southern states. This palm could be tried more in well-drained sites as a replacement for Washingtonia robusta which grows very tall with a skinny trunk. But over-irrigation and rainy weather could initiate root rot. Washingtonia filifera is shorter, has a thicker trunk, and is better suited for planting in dry urban landscapes, such as in Texas, Arizona, and California. They reportedly suffer and often die from root rot when irrigated. Select Washingtonia robusta in an irrigated landscape and for the eastern US.

Propagation is by seed.

Pests

Scales while young, palm weevil in old age, palm leaf skeletonizer and a variety of scales at any time can infest this palm.

Diseases

Trunk or root rot in wet soils may infect this tree.