The Northernmost Area for Palm Trees

Winter Hardiness

• The U.S. Department of Agriculture Plant Hardiness Zone Map delineates parts of North America based on the expected annual winter minimum temperature. Most palm species grow without much concern in zones 9 and warmer. However, in zones 7 and 8, a few palm species survive. The most cold hardy or northernmost palms survive winters in zone 7.

Types

• The needle palm (Rhapidophyllum hystrix) is the most cold-hardy species. It grows as a shrub, not a trunked palm. Of the treelike palms, the windmill palms (Trachycarpus spp.), some sabal palms (Sabal spp.) and some pindo palms (Butia spp.) can grow in zone 7. Slightly less cold tolerant but growing into USDA zone 8 are the hardy bamboo palm (Chamaedorea microspadix), Chilean wine palm (Jubaea chilensis), mazari palm (Nannorrhops ritchiana) the European fan palm (C. humilis).

Northernmost Geographies

• Using USDA zone 7 as a guideline for winter hardiness of palms, a geographical northern limit to trunked palms is shown. In North America, the northernmost latitudes associated with zone 7 occur along the Pacific Coast, mainly from Oregon northward into southwestern British Columbia. In the eastern United States, the northernmost possibility of the most cold-hardy treelike palms is the Delmarva Peninsula. In Europe, the warming waters of the Gulf Stream allow many cold hardy palms to grow in southern England as well as in countries south of the Alps. Europe overall is at a higher latitude than the United States. The European fan palm has the most northerly natural range of all palms.

Modern Trends

• Since the late 1990s, many gardening enthusiasts and plant retail companies place palms outdoors in summertime in USDA zones 4 through 6 as a seasonal garden embellishment. In the heat of summer, seemingly only tropical, frost-intolerant palms grow in northern latitudes. Without special precautionary steps, such as wrapping and heating plants or relocating them indoors into a greenhouse, these palms will not survive the winters with prolonged subfreezing temperatures, drying winds and damaging heavy snows and ice.