Northern New Hampshire is primarily in zones 5a, 4b, and 4a, making it the coldest region in the Granite State. In this article, we’ll explore each zone to help you choose the best plants for your garden.
However, if you came across this article by accident and you’re more interested in knowing the planting zones of other regions in New Hampshire, check out the articles below:
What planting zone is northern New Hampshire?
Northern New Hampshire encompasses four USDA plant hardiness zones: zones 5a, 4b, 4a, and 3b. However, most of the region is located within the first three zones, with only a small area falling into zone 3b.
Understanding which zone you’re located in is crucial for selecting plants that will thrive in this cold region. You can learn more about it in our article: How to Use the Plant Hardiness Zone Map in Your Yard.
Note: For educational purposes, we’re considering northern New Hampshire as the region above Littleton, specifically Coos County.
Let’s take a closer look at each of these planting zones:
Zone 5a
Zone 5a, with average extreme minimum temperatures of -20 to -15 F, covers the southeastern part of Coos County. This includes portions of the city of Berlin and the town of Gorham, for example.
If you’re dreaming of a lush lawn, this region is likely the best spot in the county for it. The relatively milder winter temperatures here offer a more favorable environment for grass growth. Learn more about it in our guide: The Best Grass Seed for New Hampshire Lawns.
Zone 4b
Zone 4b experiences average extreme minimum temperatures of -25 to -20 F. This zone covers the southwestern part of Coos County and partially includes cities like Lancaster, Berlin, and Northumberland. It also encompasses most of the region surrounding the Androscoggin River.
The colder temperatures in this zone require selecting hardy plants that can withstand the severe winter conditions. It also requires knowing the best time to plant grass, so the seeds can establish before winter. Check out our guide, When to Plant Grass Seed in New Hampshire, for more information.
Zone 4a
Zone 4a covers mainly the upper half of Coos County and is characterized by extreme average minimum temperatures of -30 to -25 F and a short growing season. Lancaster is partially in this zone, and towns like Colebrook and Pittsburg are also located here.
The harsh conditions in this zone mean you’ll have to choose hardy plants that can endure severe winters, like these winter flowers that bloom in the cold.
Zone 3b
Zone 3b is the coldest in the state, with average extreme minimum temperatures of -35 to -30 F. The only region of Coos County and the entire state that falls into this planting zone is the Presidential Range, particularly the high elevation areas of Mount Washington.
In this harsh environment, only dwarf vegetation can survive. The soil in this area doesn’t retain moisture well, the temperatures are consistently cold, and there is less oxygen due to the high altitude.
When to call a pro
Gardening in northern New Hampshire is not easy, as not every plant can survive the extreme conditions. Luckily, you don’t have to do everything alone. Call a local lawn care professional to help you choose the best plants for your zone and take care of planting for you. With their expertise, you can create a thriving garden even in the coldest parts of the Granite State.
Main Image Credit: Doug Kerr | Flickr | CC BY-SA 2.0
