2023 Plant Hardiness Zone Map for Louisiana. Image: USDA and Oregon State University.

Plant Hardiness

In 2023 the USDA and the Oregon State University published a new Plant Hardiness Zone map for the entire United States. This map demonstrates that our winter temperatures have become warmer over the last ten years.AHA shared this new map with gardeners, and Nora asked, “What is Deridder’s zone?” and “Are we considered to be south LA?”

Dr. Heather Kirk-Ballard wrote in Get It Growing column how to interpret the new map, “Each zone number represents a 10-degree Fahrenheit difference in average low temperatures in winter. The ‘a’ and ‘b’ denote half-zone increments, representing a 5-degree difference in average minimum winter temperatures within a main zone. Zones labeled with an ‘a’ indicate the colder part of a numbered zone while ‘b’ designates the warmer part of a zone. This provides more specific information for tailored plant selection in areas with temperature variations.

Each zone has a temperature range associated with it. For example, zone 8 has a range of 10 to 20 degrees. This means that plants recommended for zone 8 are generally able to withstand winter temperatures within this range.

The zones of Louisiana range from 8 to 10. In zone 9, average minimum winter temperatures range from 20 to 30 degrees…[emphasis added].

The answer to Nora’s first question is “9a”. In fact, all of Allen, Avoyelles, Beauregard, Evangeline, St. Landry, Rapides, and Vernon Parishes are in “9a”. In the old 2012 map, these parishes were in colder zones.

When a gardener reads plant labels at a nursery, AHA recommends looking for the “9a” on the label to ensure that the plant will tolerate our hardiness zone.

The answer to Nora’s to second question would be “yes” to being in “South LA.” Some vegetable and fruit publications by the AgCenter recommend varieties to plant in “South LA” or “Central LA” or “North LA.” Gardeners in Cenla can plant their gardens and orchards with varieties suitable for “South LA.”

Deer-rub damage on a red maple. Photo: Pastor Joe Miller, Master Gardener.

Wildlife Damage

Pastor Joe sent a picture with this message, “[I was] inspecting damage from drought. [I saw this] red maple. [Is it] deer damage? Or animal with claws. [It is] almost girdled. [Is there] anything I can do to save it?” The damage in Pastor Joe’s picture is from a buck marking his territory by rubbing his antlers on sapling trees. Garden centers sell tree protectors to avoid trunk damage to sapling trees. AHA also added that tape applied to burn wounds on people is also suitable to graft wounds on trees. So, by logical extension, burn tape would likely help with rub wounds on small trees.

2021 Quarantine map of the emerald ash borer (EAB) in Louisiana. Image: Louisiana Department of Agriculture & Forestry (LDAF)

Firewood Regulations

John sent this question, “Can you please direct me to where I can find Louisiana regulations pertaining to [transporting, or selling, or packaging firewood? I have looked and outside of north Louisiana's emerald ash borer quarantine, I cannot find anything [else].”

AHA researched John’s questions and came to the same conclusion as John. Only ten parishes in northwestern Louisiana are under quarantine for the emerald ash borer (EAB). The remainder of the state lacks any regulation regarding the movement, sale, and packaging of firewood.

Here is how the Louisiana Department of Agriculture and Forestry (LDAF) regulates EAB, “Once EAB is confirmed in a new parish, LDAF imposes a quarantine for that parish. This aims to slow the spread of EAB by restricting movement of ash timber and all hardwood firewood outside of that parish unless treated by an approved method.”

Current USDA Animal and Plant Health Inspection Service treatment standards require ash firewood to be heated to a core temperature of 140 degrees Fahrenheit for a minimum of 60 minutes.