Plant Zones in USA – Detailed Guide

Plant zones are geographic regions defined according to the different climatic conditions. They encompass different temperature ranges that are relevant for plant growth and survival. The original system of distinguishing plant zones was developed by the United States Department of Agriculture (USDA), which comprises 13 different zones situated within the United States. This distinction has been adapted and modified by other countries such as Canada to categorize plant zones in their country. 

The plant zones are also termed as ‘hardiness zones.’ Plant hardiness is the plant’s ability to thrive in adverse growing climates such as heatwaves, floods, snow, and drought. Plant genetics determine the capacity of a plant to withstand freezing temperatures without excessive damage.

Each plant displays variations of hardiness based on their genetics and adaptations. The science behind this concept is quite complicated since hardiness can be multi-faceted. It covers the hardiness of different parts or organs of a plant as well.

For example, the roots of your crop or plant might be hardier. Hence, even if the leaves with and die, the roots’ hardiness can benefit the farmer with seasonal growth.

Many plants require particular types of growing environments. You can adjust multiple components, such as type of soil, absorption of sunlight, and moisture levels. However, temperature is one thing that is difficult to maintain. Choosing plants with appropriate hardiness levels that coincide with their planting zones will give the best and most successful results.

Plant Zones in the USA
Plant Zones in the USA

Let’s dive deeper into the understanding of planting zones in the United States.

Planting Zones

You can find these areas on a growing zone map that displays precisely which plants are best suited to survive and prosper in that given area or region. If you are browsing or considering to buy new plant seeds or crops for your garden landscape, then be aware of the planting zone where your house or farm is located. ‘plant hardiness,’ ‘growing zones‘, and ‘planting zones‘  may seem complicated and confusing.

However, these terms ultimately are created to help you make better decisions about your plant and witness your vegetation and greenery’s successful growth.

USDA Designated Zones

Planting zones are broken down into thirteen regions, which can also be termed USDA planting zones. They cover all the states and territories under United States jurisdiction, including Hawaii, Puerto Rico, and Alaska. Each agricultural or geographical zone covers a 10-degree temperature range.

Site 1 is the coldest, with an average minimum winter temperature of -50 to -50 degrees Fahrenheit. On the other hand, the minimum average winter temperature of zone 13 is 60 to 70 degrees Fahrenheit.

As you can see, the zones are carefully curated to include all-climate extremities and inform the gardeners about the perfect area to start planting for the crops of plants they want to grow.

In the United States, most of the warmer zones are at the end, such as zone 9, 10, and 11. They are located in the southern half of the country and on the south of coastal limits. Higher zones can be found in Hawaii, for example, it would be located in zone 12 twelve and Puerto Rico would be located in zone thirteen.

The southern middle portion of the mainland and central coastal areas are in the intermediate zones (six, seven, and eight). Lower zones, such as zone one, can be found in Alaska. The far northern portion of the mainland’s central interior has some of the coldest zones (three, four, and five) and often have low consistency in terms of the temperature range in winter due to continentalism. Hence, this is where the zone map has its limitations in these areas.

What Is Your Planting Zone?

Why is it important to know where your gardening zone is? Once you have understood what these zones are and how they interpret climate and temperature ranges, you will focus your time and attention better on picking out the right plants.

Each of the thirteen zones on an interactive planting zone map is broken down into two parts to give 5-degree increments in each zone. Using an interactive zone map, you can discover even more options for different crops that you didn’t know you could grow in your backyard.

Limitations of USDA System

The system designed USDA is based entirely on the average annual extreme minimum temperature in an area. It is restricted in its ability to explain and pinpoint the climatic conditions a gardener may experience in a particular region. Many other aspects determine whether or not a given plant can survive in a specific zone.

Specifics of a zone alone are not adequate for predicting the survival of plants in winter. Factors such as frost dates, snowfall period, and frequency of snow can vary according to regions. Even the extreme minimum itself may not be productive when areas are compared to different countries.

For example, the United Kingdom has a vast land of in zone 8 and 9, while the United States has zones 8 and 9 in the subtropical coastal regions. Hence, an American gardener or farmer may only have to predict and prepare for cold temperatures lasting only a few days per year, while a gardener in the UK may have to plan out for several months.

Moreover, the zones do not embody any details about summer temperatures; hence the regions may have the same winter minimal temperatures but varying summer temperatures. For example, coastal Ireland and Miami are both in zone 10 but have extremely distinctive summer heat, humidity, and insolation.

In addition to lack of summer temperatures, the colder zones do not take into account the reliability of snow cover. Snow acts as an insulator against extreme cold, which keeps the root system of hibernating plants protected and safe. Hence, if the snow cover is plentiful, the roots’ temperature will remain unhinged and will not be as low as the hardiness zone.

Another limitation of the USDA zonal system is not considering the extent of low temperature within a day that a plant or flower may need to blossom. This is called vernalization which is the duration of low temperature. Plants may survive in a locality but can experience trouble if the length of a day is insufficient.

Even though the annual minimum temperature is a beneficial indicator, it is a single factor among many other crucial aspects that should be considered for plant growth and survival.

How to make use of planting zones?

Planting zones are best for gardeners growing perennial plants, since these type of plants are supposed to live beyond just one growing season. Perennial plants should be able to survive winter in your region, hence it’s essential to know how cold it can get in your area and whether a plant is hardy enough to survive extreme temperatures. 

Perennial flowers, trees, fruits, and vegetables grow best when planted in the zone suited to its needs. You will discover that winter damage occurs most often when plants are out of their comfort one. When you select seeds for a garden or field, remember to avoid selecting plants that are only slightly hardy, otherwise, you will experience winter damage, stunted growth, and losses.

Planting native strains is the absolute way to ensure a stable and prospering garden. Native plants occur where you usually live. Therefore they naturally thrive in their habitat, and you will witness them flourish.

Let’s learn more about the types of plants that could be grown in each zone in the USA:

Zone 1

This is the coldest zone in the entire United States and hence can be difficult for gardening. The majority of zone 1 is located in Alaska which has a tundra environment. The plants for survival in this region should be extremely hardy. Giving plants a head start in a controlled environment such as a greenhouse could give better results for zone 1 vegetables.

The famous zone one vegetable is; Beans, Broccoli, Cabbage, Spinach, Kale, Sweet Peas, Tomatoes, Potatoes, Radish, and Lettuce.

There are very few types of fruit trees that can survive the tundra climate. However, there are a few that you can grow; September Ruby Apple, Chokecherry, End Apple, Haskap, and Fort Mac Apple.

You could grow almost any herb as an annual crop in zone 1, such as: Basil, Mint, Oregano, Rosemary, Thyme, and Chives.

Zone 2

Zone 2 is located in both Alaska and other parts of the continental United States. This zone experiences frigid temperatures and could be an added struggle for gardeners living in these regions. High winds and drought conditions are quite common in this zone and the tundra region.

The popular vegetables you can grow in this zone are; carrots, mustard greens, swiss chard, parsnips, and onions.

Zone 2 is not a suitable region for many fruit trees. However, some hardy fruit varieties include;  Fofonoff Plum, Fall Red Apple, Korean Pine, Norkent Apple, Parkland Apple, Pembina Plum, and Garrington Chokecherry.

Juniper, Turkestan Rose, and Hyssop are some of the herbs that are manageable in zone 2.

Zone 3

This zone is prevalent in the northern regions of the United States. Like the previous two zones, this zone also faces ow moisture, extreme cold temperature, and high winds. 

These are the following vegetables that can be grown in this zone; Asparagus, Celery, Summer Squash, Winter Squash, and Cucumbers.

Many fruit trees are hardy enough for zone 3, including Cupid Cherry, Dolgo crabapple, Evans cherry, Golden Spice pear, Goodland apple, Sweet Sixteen apple, and Toka plum, Waneta plum, and Westcot apricot.

The annual herbs withstand zone 3 temperatures are: Caraway, Catnip, English chamomile, French sorrel, Garlic, Horseradish, Parsley, and Peppermint.

Zone 4

Zone 4 area covers Alaska’s coastal regions, northern regions of the states, and the western mountains. The climates of these regions share a minimum average temperature of between -30 to -20 degrees Fahrenheit.

Rhubarb is one of the most tremendous and hardy vegetables found in zone 4. Other vegetables include Eggplant, Melons, Okra, and Pumpkins.

On the other hand, many more vegetable hardy fruit trees are appropriate for planting in zone 4: Alderman Plum, Alexander apple, Buartnut, Butternut, Ewing blue plum, Nova pear, Railroad apple, summer crisp pear, and Trent apple.

The essential herbs are for zone 4 are:

Angelica, Beebalm, Garden sage, Lemon balm, Mountain mint, Thyme, and Winter savory.

Zone 5

This zone includes the southern coastal region of Alaska, the North Central United States, and New England portions. Depending on your area, some cold season vegetables may be repeated in late summer for a fall harvest, including Kale, Lettuce, Radishes, Spinach, and winter greens.

Many fruit trees are hardy to Zone 5, including, Harrow Delight pear, Honeycrisp apple Native pawpaw trees, Pink Lady apple, Snow Beauty peach, Superior plum, and Warren pear.

Hybrid mints and lavender are some of the herbs you can grow in this region.

Zone 6

This zone covers the most considerable portion of the United States. It IS known to have the mildest temperature and an average minimum temperature of -10 to 0 degrees Fahrenheit. This zone is optimal for most vegetables and fruit trees. Zone 6 gardeners have a myriad of options with seasonal growth all year round.

The garden season and adequate summer temperatures make growth of a variety of Vegetables popular. The vegetables that do considerably well in this zone are beans, lettuce, tomatoes, melons, and winter squash.

Peaches are the most abundant fruit found in zone 6. Some varieties of peaches you can grow are Jefferson, Madison, Red Globe, Nectar, and Loring.

Warm springs in zone 6 allow herbs to reseed. Some of the popular herbs are Coriander, Oregano, Dill, Chamomile and Borage.

Zone 7

This zone expands to almost 15 states in the states. Garden is this zone that has numerous plant options and is home to many nurseries and plant stores.

Popular vegetables are: Arugula, Hot peppers, Long growing season vegetables, Sweet peppers, Turnips.

A wide variety of fruit trees includes Bing cherry, Blue Java banana, Contender peach, Cortland apple, Fuji apple Rainier Sweet cherry, Red Gold nectarine, Scout apricot, Stella cherry, Turkey fig.

Sage, Tarragon, and Rue are some of the famous and easy growing herbs in this zone.

Zone 8

This is one of the warmest hardiness zones and covers a large portion of the southern region of United States.

Vegetables that thrive in the summer heat of Zone 8 include: Lettuce varieties, Cantaloupe, Field peas, Hot peppers, Okra, Tomatoes, Watermelon.

Bananas, apricots, jujube, lemon, and grapefruit are some of the popular fruits grown in this region.

Zone 9

This is considered to a year-round planting zone. Located in California, texas, florida, Arizona and gulf of mexico.

Most areas will only produce peppers, okra and extremely heat-tolerant vegetables during August. However, you’ll likely be able to grow the following vegetables throughout the winter:

Broccoli Cauliflower, Greens, Spinach Brussel sprouts, Cabbage

Avacado, olives, passionfruit and kiwi are some of the famous fruits of this zone.

Zone 10

The extreme heat of this region can prevent vegetation all year round.

Consider including these vegetables in your Zone 10 garden: Bitter melon,  Peanuts, Malabar spinach and Tomatillos.

Some of the popular fruit trees and herbs are apple guava, jackfruit, June plum, curry leaf, ginger, and miracle fruit.

Zone 11

This zone is found in Hawaii, Puerto Rico, and a few other areas. Grow tropical plants in this region.

Some of the cold seasonal vegetables appropriate for winter gardening in Zone 11 include:

Beets Cabbage Kale Radishes Sweet Peas Swiss chard and Carrots

Mango and macadamia are the best fruit trees to grow in this zone.

Zone 12 and 13

Planting Zones 12 and 13 are not found in the continental United States but are located in both Hawaii and Puerto Rico.  Plenty of vegetables can be grown in Zones 12 and 13 by planting during colder months and using shade and irrigation to reduce heat.

Plants that are heat and drought tolerant and have a short growing season, such as Bush beans, Eggplant, Hot peppers, Summer squashes, and Tomatoes. Black pepper, almond, cilantro, rosemary, and olives are some fruit, and herbs will flourish in this zone.

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These are all about Plant Zones in the USA.