The idea of a palm tree swaying in an Oklahoma yard might seem impossible, yet the answer to whether they can grow there is a qualified yes. Certain palm species possess a remarkable cold tolerance that allows them to survive the state’s challenging winters. Successfully cultivating these plants requires careful selection of the right variety and a commitment to providing specific care, particularly when temperatures plummet. This success results from understanding the regional climate and implementing protective measures.
Understanding Oklahoma’s Hardiness Zones
Oklahoma’s climate poses a significant challenge to most palm varieties due to variable winter temperatures and intense cold snaps. The state covers USDA Plant Hardiness Zones 6b, 7a, and 7b, with a small section of 8a in the far southeastern corner. These zones are defined by the average annual minimum winter temperature, which determines a plant’s ability to survive outdoors.
Zone 6b, found in the panhandle and northern areas, experiences average minimum temperatures between -5°F and 0°F. Zone 7b in the south-central region sees lows of 5°F to 10°F. Since minimum temperatures fall below the survival threshold for most traditional tropical palms, viable options are limited to a handful of specialized, cold-tolerant species. Understanding the specific temperature range for your location is the first step in selecting a palm that has a realistic chance of survival.
Palm Species That Survive the Cold
The choice of species must focus exclusively on those with exceptional cold-hardiness, capable of withstanding temperatures near or below freezing. The Needle Palm (Rhapidophyllum hystrix) is the most cold-tolerant palm in the world, surviving temperatures as low as -15°F to -10°F. This shrubby, multi-stemmed variety typically grows to about ten feet tall and does not form a traditional trunk.
The Windmill Palm (Trachycarpus fortunei) can tolerate sustained cold down to 10°F, often surviving brief dips to 0°F as it matures. This palm is known for its slender trunk covered in fibrous material and its fan-shaped fronds. The Pindo Palm (Butia capitata) is a feather-leaved variety surviving temperatures in the 5°F to 15°F range.
The European Fan Palm (Chamaerops humilis) is a multi-trunked palm with fan-shaped leaves, exhibiting cold tolerance similar to the Pindo Palm, with survival reported down to 5°F. These cold-hardy palms survive by protecting their growing point, called the spear or bud, which is the most vulnerable part of the plant. Selecting a palm rated for a hardiness zone colder than your own is advisable to account for extreme, unpredictable cold snaps.
Siting and Planting Requirements
Successful palm growth depends on the planting location and soil preparation to manage winter cold and summer heat. Palms require excellent soil drainage to prevent roots from sitting in water, which is damaging when the ground is cold.
Soil Preparation
Heavy clay soils common in Oklahoma must be amended with sand and organic matter to ensure water quickly moves away from the root zone. When planting, the root ball should be set at the same level it was in the nursery container. Avoid planting too deeply, which can invite rot.
Location Selection
The planting site should maximize winter protection while balancing summer sun exposure. A location on the south or southwest side of a building offers a beneficial microclimate, shielding the palm from harsh winter winds and maximizing solar gain. While palms prefer full sun, the intense Oklahoma summer sun can cause frond burn. Therefore, a location that receives some afternoon shade can be advantageous for smaller plants.
Critical Winterization Techniques
Protecting the palm during the coldest months is critical for survival in Oklahoma’s climate. Winterization focuses on insulating the root zone and safeguarding the growing point (the top of the trunk where new leaves emerge). A thick layer of mulch, three to six inches deep, should be applied around the base of the palm to insulate the roots and prevent the soil from freezing solid.
Before the first hard freeze, the palm’s fronds should be gathered and tied vertically into a tight bundle to protect the growing spear. The trunk and tied fronds can then be wrapped in layers of breathable insulating material, such as burlap or frost cloth. For palms in Zone 6b or 7a, or when extended deep freezes are predicted, supplemental heat is required within the wrapping.
This heat is typically provided by:
- Wrapping the trunk with heat cable.
- Stringing incandescent Christmas lights, which emit enough warmth to raise the internal temperature.
The entire structure can then be covered with a waterproof tarp or plastic. Care must be taken to ensure some ventilation on warmer days to prevent moisture buildup and rot. The protective wrapping must be completely removed in early spring once the threat of deep frost has passed to allow the palm to breathe and begin its new growth cycle.