Cold hardiness & minimum temperature

Is California Fan Palm (Washingtonia filifera)cold hardy? Hardiness zone & min temp

Also called Desert Fan Palm, Petticoat Palm.

More about california fan palm

About California Fan Palm

Washingtonia filifera · also called Desert Fan Palm, Petticoat Palm · tropical

California fan palm is the only palm native to the western United States, a stout desert species with a massive trunk and large grey-green fan fronds bearing characteristic cottony white threads between the segments. Unpruned, dead fronds form a dense 'petticoat' skirt. It is heat- and drought-hardy, tolerates cold better than most palms, and grows slower and squatter than its Mexican cousin.

Cold limit: USDA 8b-11 (one of the hardiest palms, briefly to about -8 to -10°C) · RHS H4 (15-40°C)

What california fan palm's hardiness rating actually means

Yes — california fan palm is genuinely cold hardy. Rated RHS H4 and USDA 8b-11 (one of the hardiest palms, briefly to about -8 to -10°C), it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H4 means: Hardy in an average winter across much of the temperate world. On the US scale that maps to USDA 8b-11 (one of the hardiest palms, briefly to about -8 to -10°C) — the zones where it can be left outdoors year-round.

New to these scales? The USDA hardiness zone map explained covers how the zone numbers work, and you can find your own zone with the zone finder.

Minimum temperature — and what happens below it

Minimum survivable temperature is roughly about −10 to −5 °C. California Fan Palm is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for california fan palm as it gets too cold:

It tolerates winter lows to about −10 to −5 °C once established.
Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root.
First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.

Can california fan palm go outside or overwinter — and where?

Plant it out within USDA 8b-11 (one of the hardiest palms, briefly to about -8 to -10°C) and it overwinters with little or no help.
It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy.
The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

Work back from your local frost dates with the frost-date calculator: the last spring frost and first autumn frost are what really decide when california fan palm can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

California Fan Palm hardiness — frequently asked questions

Is california fan palm cold hardy?

Yes — california fan palm is genuinely cold hardy. Rated RHS H4 and USDA 8b-11 (one of the hardiest palms, briefly to about -8 to -10°C), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. California Fan Palm is hardy across USDA 8b-11 (one of the hardiest palms, briefly to about -8 to -10°C); it belongs in the ground or a frost-proof container, not on a windowsill, and many types actively need a cold winter to perform.

What is the minimum temperature california fan palm can survive?

Minimum survivable temperature is roughly about −10 to −5 °C. California Fan Palm is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is california fan palm?

California Fan Palm is rated USDA 8b-11 (one of the hardiest palms, briefly to about -8 to -10°C) and RHS H4 — Hardy in an average winter across much of the temperate world.

Can california fan palm survive winter outside?

Plant it out within USDA 8b-11 (one of the hardiest palms, briefly to about -8 to -10°C) and it overwinters with little or no help. It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy. The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

What happens to california fan palm below its minimum temperature?

It tolerates winter lows to about −10 to −5 °C once established. Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root. First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.