Everything Your Plant Hardiness Zone Can Tell You About Planing & Caring For Trees

Microclimates and Plant Survival

Will this tree grow well where I live? This is an important question when selecting a tree for a specific place. The University of Florida’s IFAS Extension supports this view by noting that “Trees adapted to the planting site are more likely to remain standing in hurricanes.” 

To determine whether a tree you want to plant will survive the climate you live in, you need to understand the concept of plant hardiness and plant hardiness zones, also known as planting zones. These ideas help us understand which trees can survive the climate of our region. 

In this article, we define plant hardiness, plant hardiness zones, how to find microclimates, how climate change affects plant hardiness zones, and how to apply this knowledge to care for your tress.

What Is Plant Hardiness? 

Plant hardiness is a plant’s ability to survive in adverse climatic conditions. The University of Vermont Extension’s Department of Plant and Soil Science notes that “Hardiness is genetic.” Adding, “That is why some plants are hardier than others, even why some cultivars are hardier than others of the same plant.” 

Since some trees fail to survive in extreme temperatures, it’s beneficial for gardeners and farmers to know which ones will and won’t survive based on the plant hardiness zones. 

A relatable example of plant hardiness would be the palm tree. Although certain species of palm trees can withstand below freezing temperatures, these trees generally don’t thrive in areas below 40°F. 

Plant Hardiness Zone

The U.S. Forest Service defines plant hardiness zones as “the standard by which gardeners and growers can determine which plants are most likely to thrive at a location.” 

The U.S. Department of Agriculture’s (USDA) Agricultural Research Service (ARS) determines plant hardiness zones. It also produces the map used to identify different zones.

Plant hardiness zones help growers in finding out which plants will grow and thrive in their specific zone. There are currently 11 North American hardiness zones, with a 10°F difference based on the average annual minimum winter temperature. 

How Can I Find Areas With Microclimates?

While planting zones can help determine which trees to plant in a specific region, they are not absolute. One thing to remember is that you may be living in a microclimate within a specific plant hardiness zone. The Royal Meteorological Society describes a microclimate as “the distinctive climate of a small-scale area, such as a garden, park, valley or part of a city.”

Microclimates can make for drastic plant hardiness changes in some situations. One reason why it helps to identify microclimates is for selective planting in certain areas. Understanding microclimates helps take advantage of the growth potential in specific regions. 

BBC.co.uk describes some factors you can take into account when identifying microclimates: 

Landscape: The physical location and its characteristics. Variables of a landscape include elevation, longitude, and latitude, mountains, and prairies.

Relief: Includes landscape changes in height. For example, most south-facing slopes in the northern hemisphere will get more direct sunlight than the north-facing ones due to the location of the rising and setting sun. 

Activities taking place: These could be human-caused or naturally occurring. Humans are talented at taking harsh landscapes and turning them into flourishing plant areas simply by building enclosures. Nature also causes temperature changes. Natural disasters and other less drastic changes like tidal patterns affect and define microclimates. 

Effect of Climate Change on Plant Hardiness Zones

Like all other aspects of our lives, plant hardiness zones are affected by climate change. Because of changing temperatures, the plant hardiness map we see today isn’t the same as the first plant hardiness map issued in 1960. 

The map issued in 2003 places many areas a half-zone higher than previously displayed in the 1990 version. Climate.gov shows changes in plant hardiness using animations that create a visual representation of how the hardiness map changed from 1990 to 2006.

Yale University’s Yale Environment 360 states that the tropics are growing in size by about 30 miles per decade. The Tropic of Cancer in the Northern Hemisphere and the Tropic of Capricorn in the Southern Hemisphere are the lines where the sun lies directly overhead on the December and June solstices. 

Yale Environment 360 also states that: 

• The Sahara desert is currently 10% bigger since 1920. 
• The 100th meridian has shifted 140 miles east.
• Tornado Alley has shifted 500 miles east in just 30 years.
• The permafrost line in Canada moved 80 miles north in 50 years. 
• The Wheatbelt in Australia is moving south at 160 miles per decade. 

Yale estimates that the plant hardiness zones in the U.S. are moving north at about 13 miles per decade. So, what does it mean if your hardiness zone is a half-zone warmer today than previous years on the plant hardiness scale? In some cases, it means that the plants that may have been able to survive in your area a decade ago may struggle now. 

However, the National Gardening Association points out that the half-zone change in the most recent hardiness map is partly due to the enhanced methods of measuring temperature, including algorithms based on a location’s nearness to a body of water, elevation, position on the terrain, and more.

Taking Action To Reduce the Effects of Climate Change

According to the National Wildlife Federation, some states could risk losing their state trees and flowers to extinction due to climate change. The same organization also educates on ways we can reduce the effects of the changing climate:

Planting trees to absorb carbon dioxide: Trees produce oxygen that we need to survive and remove harmful carbon dioxide from the atmosphere. Carbon dioxide is known to trap heat, which causes climate change. 

Reducing water consumption: Water isn’t always consumed responsibly. There are many ways we can reduce water consumption so that we reduce the proliferation of desertification.

Composting waste: Composting our organic waste keeps trash out of landfills and provides fertile soil for growing trees. More information about composting is available on the United States Environmental Protection Agency’s (EPA) website.

Reduce the threat of invasive species: When plants and animals get introduced from another continent, there is a possibility that the natural vegetation could be adversely affected. For this reason, the U.S. Forest Service makes it a priority to prevent and control invasive species.

What Tools Can I Use To Monitor Planting Data? 

We can collect information about the trees we plant by connecting sensors to them and the soil below. 

Monitoring planting data is a modern-day commodity that needs to be taken advantage of, and various companies provide high-tech solutions. We can determine whether trees will thrive in a specific area using real-time monitoring of data and growing variables.

Below are some software tools available for monitoring planting data: 

HortControl by Phenospex: Offers a smart plant-analysis software that provides data visualization and experimental setup with control and monitoring to help growers track and study single plants or complete fields.

Climate FieldView: This is a data-connectivity platform that’s useful for monitoring planting data. With FieldView, you can monitor your crops in real time, upload historical data, and share critical information.

Bayer: Provides tools with in-field sensors that measure the soil for nitrogen, phosphorous, water, and other organic matter.

Paskal Group: Provides a wireless plant monitoring system called PhytoVision. The company says that using its tools, “Farmers are able to make data-informed decisions and more accurately provide direct support to their plants.” 

Applying Knowledge About Plant Hardiness Zones to Caring for Trees

If you’re looking to successfully enhance or create an outdoor space with trees, the first step is identifying the tree species you want to plant—you can’t determine whether a tree is fit for a specific zone if you don’t know what type of tree it is.

Luckily, there are applications like PictureThis, PlantSnap, NatureID, and Seek by iNaturalist that help identify trees, plants, bugs, and anything else in nature. The process of identifying an unknown tree or plant is quite simple. You take a picture of the plant inside the app, and the program tells you the name. 

Most apps also make it relatively simple to find out the plant’s hardiness number; you just do a search using the name of the plant you’re interested in, and you’ll get the zones suitable for that plant. For example, if you search on most apps using the ‘hardiness scale of Juniper,’ you will know that the plant can survive in zones 3-9.