In a significant update that every Louisville landscaper and gardener should note, the USDA announced a shift in Louisville’s Plant Hardiness Zone, graduating the area from a Zone 6b to Zone 7a. 

This adjustment, based on the latest climatic data, could subtly influence the plant choices for your garden or landscaping project. 

Let’s dive into what this change means and how you can adapt to optimize your green spaces in Louisville.

What Is the Plant Hardiness Zone?

A Plant Hardiness Zone, determined by the USDA, is a standard that guides gardeners and landscapers on which plants are most likely to thrive in a specific location. 

It’s based on the average annual minimum winter temperature, essentially mapping out the coldest nights of the year. 

For landscapers and gardeners, this is a crucial designation, as it helps in selecting plants that can withstand the local climate.

Why Did Louisville’s Hardiness Zone Shift?

The shift to Zone 7 indicates that Louisville is experiencing warmer temperatures than previously estimated. 

This conclusion comes from an analysis of data from over 13,000 weather stations. The USDA’s 2023 map says that Louisville is approximately 2.5 degrees warmer than its 2012 estimation.

While most of Jefferson County now falls into Zone 7, neighboring areas like Oldham and Shelby counties remain in Zone 6b, highlighting a unique microclimatic variation within the region.

What Does The New Hardiness Zone Mean For Louisville?

With Louisville now in Zone 7, you might be tempted to experiment with plants that prefer milder winters. However, caution is key. 

Despite the warmer classification, Louisville is no stranger to unexpected cold snaps and polar vortex events. (We just had one occur earlier in 2024). Because of this, it’s wise not to fill your garden completely with Zone 7 plants.

Gardeners will still want to maintain a mix of plants that can survive in a range of zones that include Louisville’s previous and current zone classifications.

What Should I Plant In Louisville With The New Hardiness Zone?

Exercise caution with filling your garden with warmer-weather plants. But these are some Zone 7 plants that more experimental Louisville gardeners could try. Just know that they may not survive if the area endures a serious freeze.

• Calla Lilies: Even with Louisville’s new zone classification, calla lilies will not work here as perennials. But they could be a fun annual to try this year. With their trumpet-like shape, they’re an elegant flower. Wait to plant until the soil is at least 65 degrees to make sure your lilies don’t freeze.
• Desert Bird of Paradise: Louisville may not be a tropical destination, but you can capture a bit of island living with the colorful Desert Bird of Paradise.
• The Hardy Banana (Musa Basjoo): Pawpaws aren’t the only fruit you can grow in Kentucky. The Hardy Banana tree just got hardier with our new zone designation. Maybe try adding one to your garden — at least as a conversation starter.

How Are Louisville Landscapers Adapting?

Local landscapers like Walnut Ridge Landscape & Design — equipped with knowledge and experience —  are likely to continue choosing hardier plants, ensuring landscape resilience against unpredictable weather. 

But landscapers also have the knowledge necessary to safeguard plants during unexpected freezes, employing strategies like heavy mulching or protective coverings.

Contact Walnut Ridge if you are interested in weatherizing your garden or want to know if you should update your landscaping in the wake of the Louisville area’s zone change.