An understanding of planting zones in the USA will shape everything about your homestead garden! USDA gardening zones is one of the most frequently asked about topics by new gardeners - for good reason.
In short, a planting zone is a number assigned your area based on its weather history and the number of days in the local growing season. This number is vital for ensuring you choose the correct seeds for your area!
The planting zone number is frequently used on seed packages and plant labels to allow you to know if what you want to plant will be able to survive your winter and/or your summer weather. On the USDA’s website, you will find a helpful map to determine your planting zone.
Interpreting Label Information About Planting Zones in USA
For example... let’s consider a plant label which says, “Zones 4-8a/4-6”. The first set of numbers are the planting or hardiness zones in which the plant will thrive and produce.
Each zone is assigned an “a” and a “b” section. Don’t let this confuse you. The “a” simply indicates that winter temperatures are usually 5 degrees cooler than in “b” of the same planting zone.
The second set of numbers represents the heat zone in which the plant will thrive and produce. The heat zone map was developed by The American Horticultural Society. They divided a map into 12 zones based on graduated temperatures. The lower the number, the cooler the summer temperatures. You can check their site to determine your heat zone.
Not all seed or plant labels will have two sets of numbers because some of them do not include the heat zone information.
If you see only one set of numbers on the label you can know they represent the planting zone recommendations.
Knowing Your Planting Zone For Successful Gardening
The most important reason I can give you for why knowing your planting zone is essential for successful gardening is the time, energy, and money it saves you.
When planning your garden you will know to look for plants recommended for your planting zone. This will prevent wasted money on purchasing plants that won’t grow in your area. It also means you’ll have to purchase food to replace the crops which fail.
Planting Zones Are Helpful, But Not The Only Consideration
While knowing your planting and heat zone is beneficial, it only gives you part of the picture. When establishing these zones, changing weather patterns and micro-climates are not taken into account. A micro-climate is a tiny region within an area which has different weather from the region as a whole.
As an example, friends who live at 3500 feet in the mountains of the Idaho Panhandle often have snow and risk crop failure even in July while friends in the same region at 3000 feet don’t see snow past the first part of May.
I also have a friend who lives at 3250 feet in the same area who grows the most beautiful sweet corn while my friends at 2500 feet have feeble crops at best. He believes it’s because of his micro-climate. He has a longer growing season because heat rises from the valley as the winds begin to change from summer to fall giving him 15 more days of warmth in the fall than the valley has.
To determine if you live in a micro-climate, make a note of the temperature readings on your homestead for a whole growing season. Take them in the morning and in the evening. Then compare them to the records of your region. You can find these on your local weather station or on the USNA’s website.
Why You Should Know Your Expected Frost Dates
The frost hardiness of plants is crucial to successful gardening. Some plants can take a light frost while others are killed by the slightest frost. Before planting, know the predicted date of the last frost for your area.
Planting too early will cause tender seedlings to be killed. Using a greenhouse can extend your growing season as your seedlings will be protected from possible frost exposure.
Likewise, know your first predicted frost date to harvest or protect susceptible fruits before the frost can kill them. Keep a watchful eye on your local weather predictions during spring and fall to be aware of possible frost.
The Importance of a Garden Journal
The importance of keeping a garden journal cannot be overstated for many reasons! In the case of planting zones and frost dates, it can be crucial. Record the date of your first frost and the date of your last frost and compare to the predicted dates for each. This will help you know how to better plan your garden over time.
Almanacs and planting zones offer us guidelines but remember, they cannot account for micro-climates and changes in weather patterns. The most beneficial resource is to talk with experienced gardeners who share the same growing conditions as you. They are a wealth of information and usually enjoy sharing their experience!
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