Washingtonia robusta

Mexican Range and Botanical Background

The Mexican fan palm widely known as Washingtonia robusta is native to south-central and southern Baja California, Mexico. It occurs in desert and dry shrubland landscapes but remains closely tied to dependable subsurface water, springs, canyon bottoms and oases.

The plant is also classified as Washingtonia filifera var. robusta in some botanical treatments, while W. robusta remains the familiar species name in horticulture. Birds eat and disperse the fruits, and planted palms have naturalised or become invasive in warm regions where water is available.

Care for palms in containers

Repotting, support and feeding: Repot before circling roots become tightly congested, retaining a deep stable container and leaving the stem base at its existing level. Feed with a complete palm fertiliser containing micronutrients during spring and summer. Remove only entirely brown fronds and never cut the central spear or top the trunk, because the single growing point cannot regrow. Propagation is from seed, not offsets or trunk sections.

Watering and root care: In a cool winter position, water much less and let a greater part of the substrate dry, without leaving the roots completely dry for months. Use a deep, freely drained palm mix and water thoroughly in warm sunny weather as the upper layer begins drying. Do not leave the root ball standing in water, but do not subject active fine roots to repeated extreme drought.

Light, temperature and settling in: Washingtonia robusta needs outdoor full sun during the frost-free season. Acclimatise it gradually before placing it in full exposure. Low indoor light cannot support its naturally fast growth and slender trunk. Bring a container plant into a bright, cool, frost-free place before sustained freezing; this palm is not reliably hardy through a German winter, especially while young or potted. Keep the young palm in its original container until it is holding the spear firmly and resuming root or frond growth; do not disturb the roots or remove healthy fronds during recovery.

Pests, Symptoms and Solutions

Weak elongated new fans, yellowing and mite pressure in a warm dark winter position point to inadequate light combined with excessive root moisture. Move the palm to the brightest cool frost-free conditions available and reduce irrigation only after checking the root ball. A loose spear or soft crown after cold wet exposure needs protection from further moisture and close monitoring.

Mites, scale and nutrient disorders need separate evidence. Look for pale speckling or webbing, identifiable covers, and root or potting mix-pH problems behind patterned yellowing. Do not use fertiliser to compensate for cold roots or insufficient light.

A palm borer can leave sawdust, cocoons or tunnels in the crown. Repeated notches, rows of holes in opening fans, a fermented smell or unusual drying of the centre leaf add further warning.

Keep the specimen apart from other palms and request professional plant-health advice. Threadlike leaf fibres and a hanging skirt of old fronds are normal species features.

Keep Washingtonia robusta away from children and pets

• Keep this plant away from children, cats and dogs.
• Its effects after chewing or swallowing are unclear, and plant material can still cause an upset stomach.
• Contact a veterinarian or medical professional if symptoms develop or do not settle.

Washingtonia robusta and Washingtonia filifera var. robusta: why did the name change?

Washingtonia commemorates George Washington, the first president of the United States. The Latin epithet robusta means robust, strong or stout.

Hermann Wendland established the genus Washingtonia in 1879 in Botanische Zeitung (Berlin), volume 37, page 68.

Hermann Wendland first described Washingtonia robusta in 1883 in Garten-Zeitung (Berlin), volume 2, page 198.

Kew’s World Checklist treats Washingtonia robusta as a synonym of Washingtonia filifera var. robusta. Samuel Bonsall Parish placed the species in Washingtonia as Washingtonia filifera var. robusta in 1907 in Botanical Gazette, volume 44, page 420.