Heat Zones: A Guide for Plant Selection
What are Heat Zones?
Heat zones are similar to cold hardiness zones, but they focus on summer temperatures instead of winter temperatures. The American Horticultural Society (AHS) developed a “Plant Heat Zone Map” that divides the United States into twelve numbered zones based on the average number of “heat days” per year – days that temperatures rise above 86°F (30°C).
The area with the least heat days (less than one) is in zone 1, while those with the most (more than 210) heat days are in zone 12.
Why are Heat Zones Important?
Heat zones are important for gardeners because they indicate which plants can tolerate the summer heat in their area. Just because a plant can survive the winter temperatures in your region doesn’t mean it can handle the summer heat.
For example, a tropical plant might thrive in USDA plant hardiness zones 10-12, but it may not be able to tolerate the high heat and humidity of a zone 12 summer.
How to Use Heat Zones
When selecting plants for your garden, it’s important to consider both the hardiness zone and the heat zone for your area. You can find this information on plant labels or by asking at your local garden store.
The first number in the heat range represents the hottest area the plant can tolerate, while the second number is the lowest heat it can tolerate.
For example, a plant with a heat zone range of 9-11 can tolerate temperatures up to 110°F (43°C) but can also survive in areas with as few as 20 heat days per year.
Tips for Selecting Plants for Your Heat Zone
Here are some tips for selecting plants that can tolerate the summer heat in your area:
- Choose plants that are native to your region. Native plants are adapted to the local climate and are more likely to thrive in your garden.
- Look for plants that are labeled as “heat tolerant” or “drought tolerant.” These plants are more likely to be able to withstand high temperatures and low moisture levels.
- Consider planting trees and shrubs to provide shade for your other plants. Shade can help to reduce the temperature of your garden and make it more comfortable for your plants.
- Water your plants deeply and regularly, especially during hot, dry weather. Deep watering encourages deep root growth, which helps plants to anchor themselves in the soil and withstand drought conditions.
- Mulch around your plants to help retain moisture and regulate soil temperature. Mulch can also help to suppress weeds, which compete with your plants for water and nutrients.
Heat Zones and Climate Change
Climate change is causing summers to become hotter and longer in many parts of the world. This is making it more important than ever to consider heat zones when selecting plants for your garden.
By choosing plants that are adapted to your local climate, you can help to ensure that your garden will continue to thrive in the years to come.
Conclusion
Heat zones are an important tool for gardeners in warm climates. By understanding heat zones and selecting plants that are adapted to your local climate, you can create a beautiful and thriving garden that will provide you with years of enjoyment.
