Successful plant growers understand that there are plenty of factors that affect a plant’s survival. It is not just a matter of using the correct soil type, providing plenty of water, and adding fertilizers.
Many of the factors that allow a plant to thrive, survive, and produce beautiful buds and flowers are beyond our control. Consider climate change, heat, cold, wind, snow, soil type, moisture, pollution, light, and humidity as examples.
You also have to look at where you plant your greens and the kind of greens that can flourish in your area. This can be a little overwhelming for aspiring green thumbs so expert advice and recommendations based on decades of data will do wonders for your foliage.
This is where the plant hardiness zones come in.
Knowing What Plant Hardiness Is
Different plants flourish and grow in different ways depending on their optimal temperature ranges. This is called their hardiness.
Plant hardiness is your plant’s ability to thrive in natural climate conditions like heat, cold, drought, and flood. Each plant’s hardiness is influenced by its genetics and environmental adaptability. Even the parts of a single plant can have different hardiness levels.
For instance, winter can lead to a perennial plant’s death, but the roots themselves may have sufficient hardiness levels which allow them to sprout in spring.
Defining Plant Hardiness Zones
Plants have specific cold and hot tolerances. To help plant growers achieve better outcomes, the United States Department of Agriculture (USDA) plant hardiness zone map was established.
The USDA plant hardiness zone map serves as a guide for plant growers and home gardeners to identify the best and most suitable plants to cultivate based on their location.
About the USDA Plant Hardiness Zone Map
The combined efforts of the USDA and Harvard’s Arnold Arboretum resulted in the Plant Hardiness Zone Map which was released in the 1960s. It was a product of thirty years of data gathering and analysis that categorized temperature bands in the US.
It has been a continuous work in progress with the most recent map created in 2012. The map is broken down into 13 primary zones based on each location’s lowest average temperature. The USDA map is divided and classified into 10 degrees Fahrenheit zones.
Interactive Geographic Information System Mapping
Today, the USDA plant hardiness zone map can be used as an interactive geographic information system mapping or GIS-based representation. You can also use your zip code to identify the zone your location falls under.
There are no printed maps of the USDA hardiness zones, but you can download and have them printed in your preferred size and resolution.
Understanding the USDA Hardiness Zone Map
The USDA zone, which is sometimes referred to as the planting zone, encompasses the entire US including Alaska, Hawaii, and Puerto Rico. Every agricultural area includes a 10-degree range.
By knowing which zone you are under, you will be better at choosing plants in your area that have higher chances of surviving and completing their growth cycle. As a plant grower, you can invest your attention, effort, money, and time in plants with higher survival rates, especially during the winter.
Here are the 13 different planting zones and some helpful information that can help you make smarter decisions.
- Planting Zone 1 – Beans, Broccoli, Cabbage, Tomatoes
- Planting Zone 2 – Herbs, Carrots, Onions, Parsnips
- Planting Zone 3 – Cucumbers, Winter squash, Garlic
- Planting Zone 4 – Eggplants, melons, and pumpkins
- Planting Zone 5 – Lavender, hybrid mints, and calamint
- Planting Zone 6 – Watermelons, Coriander, and dill
- Planting Zone 7 – Arugula, hot peppers, and turnips
- Planting Zone 8 – Okras, jujubes, and grapefruits
- Planting Zone 9 – Fruitful and green gardens
- Planting Zone 10 – Cool-season crops, peas, and radishes
- Planting Zone 11 – Citrus trees and tropical plants
- Planting Zone 12 – Cilantro, kalanchoes, basil, and bananas
- Planting Zone 13 – heat-loving exotic tropical fruits and plants
Planting Zone 1
This growing zone is tagged as the coldest zone in the United States with an average annual minimum temperature of -60°F to -50°F. This is one of the most challenging places to do some gardening.
Alaska is generally under this zone. Due to its tremendously harsh tundra environment, the plants you choose should have drought tolerance and extreme cold hardiness.
Read our blog: 11 Must-Know Tips To Growing Tomatoes Indoors
Go For Endemic Plants and Annuals
Plants native to these areas are practical choices because they have already fully adapted to the year-round conditions. Another option would be to opt for annuals because it won’t be necessary for them to survive the winter season.
Some non-native perennial plants are also worth planting in zone 1 as long as proper care is provided.
In zone 1, you can plant vegetables like beans, broccoli, cabbage, kale, radish, sweet peas, and tomatoes. Herbs like chimes, basil, mint, oregano, and thyme are also likely to thrive in a tundra environment.
Planting Zone 2
Some areas in Alaska and the continental US belong to Zone 2. These places have an average minimum temperature of -50°F to -40°F so it shares some of the challenges as Zone 1.
Native plants and annuals are still the best plant choices when living here. You can plant the same vegetables and herbs as suggested in zone 1, but you can add carrots, onions, parsnips, and hyssops to the list. Fruit trees like the Korean pine and the fall red apple can also thrive in these temperatures.
Planting Zone 3
The higher altitude areas of Alaska and North America belong to zone 3. Based on your geographic area, your plants should be able to withstand strong winds, low moisture, and cold temperatures of -40°F to -30°F. It is one of the most brutal cold-hardiness zones on the map.
There are minimal plant choices in this zone because the growing season is limited. You can prolong your vegetable’s and flowers’ growing time by cultivating them indoors at the beginning or using a greenhouse.
Grow Zone 1 and 2 Plants With Some Additions
The hardy plants of zone 1 and 2 can still be planted in zone 3 alongside cucumbers, winter squash, garlic, and peppermint.
The good news is there are enough trees that will thrive in this zone. You can plant some cupid cherries, early gold pears, Toka plums, and Westcott apricots.
If you’re from this zone, read our blog on how to grow garlic indoors.
Planting Zone 4
The challenge with this zone is the short growing season. This impacts the budding of vegetables and the blooming of flowers. The areas belonging to this zone are the southern coastal regions of Alaska and the northern parts of the US. Areas with high elevation in the western mountains usually fall into this planting zone.
With average annual minimum winter temperatures going as low as -30°F to -20°F, these are generally considered more relaxed areas where mulch layers can be beneficial during the winter season.
Eggplants, melons, and pumpkins are good plant choices for this zone. Herbs like bee balm and lemon balm work as well. Alexander apples, nova pears, and butternut trees also grow well in these temperatures.
Planting Zone 5
Moderately cold but still featuring a shorter growing season, Zone 5 includes a large assortment of environments. With the southern region of Alaska, north-central US, and parts of New England belonging to this planting zone, you need plants that can readily adapt to changes in their surroundings.
Depending on where exactly you are located, you can plant some cool-season veggies that can be replanted in the last weeks of summer — just in time for a fall harvest. You can choose between winter greens, spinach, and some kale. Perennial herbs that can thrive in zone 5 are lavender, hybrid mints, and calamint.
Dive into the exciting world of growing kale indoors.
Planting Zone 6
This covers most of the US. If you’re based in a zone 6 area, you usually enjoy a mild climate of -10°F to 0°F. Thus, you have the best of both seasons — the cold winter and the full sun of summer. This is an ideal climate for landscaping and gardening because you can take advantage of the summer, fall, and spring seasons.
As a result, you have plenty of plants to choose from. The temperature is cool enough to let some asparagus and rhubarb grow while being sufficient and suitable for watermelons. Coriander and dill are at their healthiest in this zone.
Planting Zone 7
Fifteen US states belong to this zone that includes North Carolina, Maryland, and Utah. These areas experience cool winters with an average minimum temperature of 0°F to 10°F.
In zone number 7, you have to be more conscious of the changing climate’s impact on your plants. The early spring cold and frost can harm growing vegetables while the long summer can cause your plants to become dehydrated. You’ll need to strike the perfect balance between the elements.
Arugula, hot peppers, and turnips are vegetable choices that are highly recommended for zone 7. Sage and tarragon will thrive in these areas.
Planting Zone 8
One of the warmest plant hardiness zones, the southern regions of the US belong here. Plant growers can make the most of hot summers and gentle winters to cultivate some cantaloupes, okras, jujubes, grapefruits, and sage.
saturday’s #okra haul from the #yarden. also some bugs that are going insane in my tomato plants. there’s dozens of them. they’re very interested in digging holes in the compost area. #garden #nature #NaturePhotography #Tomatoes 🍅🍅🍅🌶️🌶️🌶️🍓🍓🍓🥒🥒🥒 pic.twitter.com/vQRzLCW2Sp
— s. holland III, gardener 🍅 (@sholland_iii) August 22, 2020
Planting Zone 9
The U.S. Department of Agriculture singled out zone 9 as the planting zone of choice thanks to its hot summers and less frigid winters. Think of gulf coast states like Arizona, California, Florida, and Texas to understand how fruitful and green gardens in Zone 9 remain the entire year.
With a minimum average temperature of 20°F to 30°F, the main challenge for growers is excessive heat during the summer. It’s been known to cause gardeners to start cultivating plants during winter, spring, and fall instead.
Planting Zone 10
Tropical plants that need minimal watering will do well in this zone. Southern California, Southern Florida, and Hawaii are the three states that fall under Zone 10.
There are no freezing temperatures here, but the extreme summer heat of 30°F to 40°F restricts possibilities. Similar to zone 9, tropical plants are your best option in this zone. During the first frost, cool-season crops like peas and radishes can also be planted.
Planting Zone 11
This zone has warmer climates with an average minimum winter temperature of 40°F to 50°F. Hawaii, Florida Keys, Puerto Rico, and smaller areas of the Continental US all belong in zone 11. They face zero problems with cold hardiness because there are no frost days at all.
The main challenge here is finding plants that can withstand the heat of the area. Citrus trees, tropical plants, and some exotic plant species like the jaboticaba (also known as the Brazilian grape tree) enjoy the heat of zone 11 and flourish beautifully.
Planting Zones 12 and 13
Both planting zones are already outside the United States and are located in the islands of Hawaii and Puerto Rico. With the highest temperatures in the list of 50°F to 70°F, your choice of plants should be able to take extreme heat.
This is the hottest of all USDA hardiness zones. The best plants for these areas are heat-loving exotic tropical fruits and plants.
Plants endemic to these areas are of course recommended, but you can also grow cilantro, kalanchoes, basil, anise, and bananas. They have a reasonable survival rate especially when additional care is provided.
— Bizz Directions (@usbizzdirection) September 1, 2018
Advantages of Knowing Your Hardiness Zones
The hardiness zone map is not a perfect and fixed science. It can be amended and changed, but it’s still a useful guideline for plant growers.
Being aware of these zones, particularly the one you belong to will serve you well as you make plans on what to grow and when. Additionally, you can look forward to:
- Planning ahead of time before the extreme cold or heat hits your area
- Coming up with remediation and protection strategies for your plants
- Making suitable adjustments to support the survival of your plants
- Maximizing your harvest and producing quality fruits and flowers
- Investing in the right kinds of plants, tools, and accessories
- Reducing the risk of revenue loss and avoiding the untimely death of your plants
You can try cultivating plants near your zone and take preventive measures by adding and removing carefully selected plants based on the USDA Hardiness Zone Map.
Knowledge Is Power
Knowing plant hardiness levels and the plant hardiness zones provides you with the best chance of having a positive and productive gardening experience. The USDA’s Hardiness Zone Map allows you to leverage data in your area from the past 30 years, a much better option than going through a trial-and-error process or using information from plant tags.
As Sir Francis Bacon said, “knowledge is power.” This is no less true when it comes to the US Hardiness Zone Map.