What is a Frost Date?

Photo of frost cabbage

Planning a spring garden is a lot of fun each year. There’s so much to look forward to like getting outside again, digging in the dirt, and watching planted seeds as they begin to grow into plants. Whether you prefer growing vegetables or enjoy watching flowering plants produce beautifully colored flowers, gardening is rewarding and fun.

But before you can get started you have to be aware of the frost date. Planting too early can mean a failed crop because it’s too cold for plants to germinate, sprout, and grow. Planting too late can mean you miss the best window for your plants to be fruitful. The frost date is key to knowing when to plant so your garden is successful.

What is a frost date? A frost date pertains to both spring and fall. In the spring, the frost date is the date you can expect the last freeze. The fall is the opposite or the date you should expect the first freeze as the seasons turn toward cooler months. The expected frost dates are calculated using the current climatic conditions in the area along with historical data.

Why is the frost date important for gardening?

The expected last frost in spring and the first frost in fall help determine a time frame to plan your gardening activities. Some plants are very delicate and cannot handle cooler air temperatures. They have to planted well past the chance of frost to ensure they will grow and thrive. If you are planning a fall garden, knowing the right time to plant and harvest food-bearing plants is important. For other plants like flowers, you want to bring them inside if possible before the first chance of frost in the fall.

How are vegetable gardens affected by the last spring frost?

Photo of frost grass

 

The last spring frost determines when seeds will begin to germinate. Many vegetable plants cannot survive the cooler nighttime temperatures in early spring. It really is about knowing when to plant specific types of plants.  There are very well-defined spring crops and warm-season crops.

  • Spring crops can handle temperatures at or above 32 degrees. Examples include lettuce, spinach, Brussels sprouts, carrots, beets, and radishes.
  • Warm-season crops don’t do well in the cooler spring temperatures. They need to be planted once the temperature stays above 55 degrees. These include cucumbers, tomatoes, and peppers.

How do you know when to plant? If you purchase seed packets, the planting information pertaining to the last frost dates is on the packet. Nursery tags on plants will also contain planting guidelines for each specific plant. You can plan your garden based on this information.

Isn’t the Frost Date the Same Every Year?

The dates for the first and last frosts fluctuate each year. Once spring gets close, you may hear the weather forecaster talking about when you can expect the last frost in your region. The growing season each year stays close to the same time frame. It is basically the time between spring’s last frost and fall’s first frost. Depending on the year’s weather patterns, they may change slightly from year to year.

Navigating Frost Dates

USDA Plant hardiness zone map

The Farmer’s Almanac is a good source for finding frost dates in your region. How are you supposed to choose a date to plant your garden plants if the date changes? The frost date is defined by the day it becomes a 50 percent chance of being free of frost. Of course, this means there is just as much of a chance it will frost or will not frost on that date. To ensure your plants are safe, you will want to adjust the date by about two weeks. In the spring, you’ll plan your planting schedule to begin two weeks later than the frost date. In the fall, you’ll adjust it back two weeks for planning planting and harvesting. There are several ways to determine your region’s frost dates.

Frost Dates by Zip Code. A lot of people use their zip code to find their region’s frost dates. There are several websites that will give you the proposed frost date based on your zip code. If you use a site like the National Gardening Association or the Old Famer’s Almanac, just take into account these are average frost dates based on historical and present data. There may be climatic differences in your area.

Frost Dates by Hardiness Zone. A Plant Hardiness Zone Map is provided by the USDA. It shows you what planting zone you live in. This map can be useful for knowing when to plant seeds and manage perennials. Most seed packets will have a copy of the PHZM to help you identify your zone so you will know when it’s safe to plant the seeds.

What can I plant outside before the last frost date of spring?

It may take a bit of patience on your part to wait on planting some of your flowers and vegetables. You can plant your cool-season veggies and flowers. Tomatoes are an example of a plant that will grow well even in the chilly spring temperatures. They can also be planted later in the summer for a fall harvest.

Your soil needs to be thawed enough to dig in. Your cooler season veggies and flowers can be planted directly in the garden. Other vegetables that cannot handle cooler temperatures will need to be started indoors and transplanted later on when the weather is more favorable for their survival. Annual flowers like snapdragons and pansies start showing up in garden centers in the early spring months. These plants are hardy and can handle cooler temperatures and continue to bloom.

In Conclusion

Frost dates are everything when planning your garden. They help you know when it is safe to plant in the spring and fall. There are a number of resources and date charts readily available to help you determine the frost dates in your region so you can keep your plants safe.  

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