What is a hardiness zone? It is a geographic area defined to encompass a certain range of climatic conditions relevant to plant growth and survival.
UNDERSTANDING YOUR ZONE
What zone do you live in? Why do yo need to know the answer to this question? Because the plant hardiness zone you live in is one of the most important factors affecting which plants will survive and thrive in your garden.
All the hardiness zones are based on the minimum annual winter temperature for each region and are broken down into 11 hardiness zones.
The U.S. Dept. of Agriculture mapped the climate zones to help gardeners and farmers select the most, hardy plants and crop for their zone. See this interactive hardiness zone map from the U.S.D.A. and find information on your zone.
11 HARDINESS ZONES
The 11 hardiness zones reflect North America’s enormous climate diversity.
The U.S.D.A. divides North America into separate zones, with each zone divided by 10-degree increments.
Zone 1 is a near-Artic zone, found mostly in Canada and Alaska, where winter temperatures drop to below -50°F.
At the other end of the spectrum is Tropical zone 11, found mostly in Florida and Hawaii, where it rarely dips below 40°F.
Zones 2-10 are further broken down into a and b zones, which are defined by 5 degree increments.
And lastly, the zones are broken down further into four broad categories: The Cold Zone, Temperate Zone, Warm Zone, and Hot Zone.
Let’s visit each category, starting with the Cold Zone.
The Cold Zone
The Cold Zone includes zones 1-4. These hardiness zones are located throughout the upper half of the United States and Canada.
The lowest average winter temperature indicates the zone. Below is a breakdown of each zones lowest temperatures.
- Below-50°F or Below -46°C
- -50°F to -40°F or -46° to -40°C
- -40° to -30°F or -40° to-34°C
- -30° to 20°F or -34° to 29°C
The soil in hardiness zones 1-4 is slow to warm in the Spring. For this reason, perennials and shrubs that are already in the ground do best because they are already established and ready from their winter nap to produce beautiful buds and blossoms.
Some plants thrive more in a cooler climate and therefore do well in zones 1-4. A few of the plants that do well in these zones include Peonies, Delphiniums, and Lilacs.
Because the seasons are shorter in zones 1-4 it is wise to plant a variety of evergreen trees, ornamental grasses, and hedges to add beauty to your winter yard as well as providing barriers and windbreaks to help protect your plants.
Also, using raised beds to plant your vegetables and herbs can increase your growing time because the beds will warm up faster in the Spring.
All cool-natured plants, vegetables, and herbs grow and thrive in these zones.
Some examples of cool-natured plants include: beets, broccoli, cabbage, carrots, cauliflower, chives, as well as kale, lettuce, and spinach.
For warmer-natured plants you can start seeds indoors. Or, you can warm the soil outside by using black plastic mulch.
Ok, now that we have covered the Cold Zone let’s move on to the Temperate Zone
The Temperate Zone
The Temperate Zones include hardiness zone 5 to 6. Located mostly in the middle, United States. The lowest average winter temperature in these hardiness zones are as follows
- -20° to -10°F or -29° to -23°C
- -10° to 0°F or -23° to -18°C
Hardiness zones 5 and 6 provide you with four distinct seasons. You can have a variety of plants growing in your yard for each.
The longer seasons provide the opportunity to plant earlier in the season and to have a longer time to grow.
Plant colder-natured plants in early Spring then plant the warmer-natured plants in late Spring or early Summer.
As a result, starting the garden early with Spring-flowering bulbs, then Summer perennials and shrubs, as well as, fall blooming plants and colorful trees you can provide yourself with a beautiful yard all year!
And furthermore, adding Evergreens and Ornamental plants for an attractive winter garden, will increase the beauty of your yard year-round. The possibilities are endless!
Next, we will discuss the Warm Zone.
The Warm Zone
The Warm Zone includes zones 7 to 8.
Zones 7 and 8 include the lower United States. Below you’ll find lowest minimum average temperature for this region.
- 0° to 10°F or -18° to -12°C
- 10° to 20°F or -12° to -7°C
Because hardiness zones 7 and 8 provide longer growing season some Spring-flowering plants may suffer from a Short winter dormancy, but usually can be enjoyed for one to two seasons.
Evergreen Azaleas, Camellias, and Hydrangeas grow with ease in this region.
In shaded area’s Spring blooming wildflowers, hardy ferns, and Hosta’s thrive in these zones.
Tomatoes and peppers produce extremely well do to the long hot summers in these area’s as do Okra, sweet potatoes, and field peas.
Beneficial Insects and Bugs
Choose plants that host beneficial bugs such as ladybugs, lacewings, and bees. Because, in this region the harmful insects and bugs have a longer period of time to produce and multiply therefore, causing more damage to plants. By choosing plants that host beneficial insects and bugs, it helps to cut down on the harmful insects that destroy your plants. Otherwise, the beneficial bugs help to keep the unwanted insect population in check which contributes to the success of your garden.
Now, that we understand some about the Warm zone, let’s talk about our last region, the Hot Zone.
The Hot Zone includes zones 9 to 11.
Hardiness zones 9 -11 is located within the lower United States, with zone 11 being limited to Hawaii, Los Angeles and San Diego area’s, as well as Southernmost Florida.
The average annual extreme minimum temperature in zones 9-11 are as follows:
- 20° to30°F or -6.7° to -1.1°C
- 30° to 40°F or -1.1° to 4.4°C
- 60° to 70° or 15.6° to 21.1°C
Growing seasons in this region are Fall, Winter, and Spring, with Summer being somewhat hot to garden. The tropical temperatures make for optimal growing in these regions.
In a more tropical area, you will find growing: Spanish moss, tropical trees, and ground cover.
Other plants and herbs such as rosemary, fuchsia, and gardenias grow well in tropical regions as well.
Also, semi-tropical fruits, including guava, papaya, and all types of citrus, grow abundantly in this region.
If managed well, your garden can grow and produce all year-round.
Your zone is not the only thing that determines whether or not a plant will thrive in your garden.
Here are some other factors that include:
- Heat and day-time temperatures
- Rain and snowfall
- Cloud cover
And when choosing plants, keep this in mind:
- Choose plants, trees and shrubs that are hardy to your region.
- Be certain a plant is hardy to your region.
Just a Note: To find out if plants are hardy to your region consult a local nursery or a knowledgeable gardener in your area.
KNOW YOUR STATE
And, it is good to know that each state can have more than one zone per state. That is, in some areas of the state it may be higher in elevation, such as mountain regions, where as some other regions of the state may be more low lands, and desert area.
Otherwise, the mountain region may be a zone 3 or 4, where as the desert region of the state may be a 6 or 7.
To look up your state to find your exact zone you will find your state map at USDA.org or The Spruce.com.
SUMMING IT UP
In concluding What is a hardiness zone?, I hope that you understand how to tell what zone you live in so it will help you to know what to plant, and when to plant. As a result, you can create a thriving productive garden! One you can enjoy throughout the season!
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