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Fall frost seeds

Working with Frost Dates

All gardeners need to understand how to work with first and last Average Frost Dates. Keeping these dates in mind provides a very good idea of how early to plant different kinds of seeds, and how long to expect a growing season to last.

All vegetables take a certain amount of time to mature before they are ready to harvest, so it’s crucial to provide that time. There is no point sowing tomato seeds in July, because they take several days (or weeks) to germinate, and the plants will not be mature enough to begin flowering for at least a month after that. By the time the first fruits are ripening, the weather will begin cooling down, which is no good for tomatoes.

What is frost?

As air temperature cools after the sun goes down, there is a certain point at which water vapour in humid air condenses into liquid water, and comes out of the atmosphere onto solid surfaces. This is known as the dew point: The temperature at which dew forms from spring to fall. When solid surfaces are cooled below the dew point of the air, and it’s below the freezing point of water, the water vapour condenses as frost. Simply put, frost is just frozen dew, but they form in different ways.

Frost dates are not set in stone. We look at the past 30 years and achieve an average date for the last frost in spring and the first in the fall. This information can only be thought of as a very general guide simply because some springs are very warm and some are long and cold. The actual frost date can fluctuate by a month or more.

Microclimates and altitude also influence frost dates. In sheltered English Bay in Vancouver, the last average frost date might be weeks earlier than it is on nearby Burnaby Mountain. So a last average frost date for Vancouver (March 28th) must be taken as a broad indication only.

How to Use Frost Dates

All plants have different requirements. Some seeds need warm soil to germinate, while others prefer to sprout when it’s still quite cold. So growing instructions really are specific to the plant in question. As the How to Grow Guides on this website show, some seeds should be started indoors 6-8 weeks before last frost. Vancouver gardeners can calculate (based on the March 28th frost average) that they should start such seeds between February 1st and 15th. Earlier than that will result in transplants that are too big, and later will result in transplants that are too small, or that have to go out later in spring. In Kelowna, the last average frost date is May 19th, so a Kelowna gardener would start the same seeds around the third week of March to the first week of April.

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The first average frost date in Vancouver is November 2nd. But the nighttime temperatures prior to that date will be getting too cold for tender plants like tomatoes and peppers to be outside without protection. Plants like some pumpkins or chili peppers, that require a full 120 days to maturity, will have to be given an early start in order to mature before it gets too cold.

Extending the Season with Crop Protection

With the frost dates in mind, the actual growing season can be extended by several weeks in both spring and fall through the use of crop protection. We recommend the use of Raised Garden Beds in the home garden, as they provide extra drainage, and will warm faster in brief winter sunny periods. Raised beds are easy to modify for use with cloche cover, wind protection, and heavy row cover. Used in combination, these methods can ensure a very early start to the season, and a prolonged harvest well into winter.

If certain crops are not quite ready and frost is in the forecast, simply lay down some heavyweight row cover over the row, and hold it in place with stones or ground staples. This fabric acts as a blanket, protecting crops from the potential danger of frost. It’s easy to install over raised beds, or even over farm rows.

An informational resource of the Victory Seed Company

Based on statistics, there is a 10% chance that a frost will occur outside of the dates listed. Whether or not a specific plant will be damaged depends on the type of plant, the maturity of the plant, the temperature, the duration, as well as many other variables.

Data Source: “Climatography of the U.S. No. 20, Supplement No. 1″, 1988, National Climatic Data Center, National Oceanic and Atmospheric Administration, U.S. Department of Commerce. NCDC Climate Products

Frost Date Chart: First and Last Frost Dates Across North America

Frost dates are important for gardeners to know, as they signal the start and end of the gardening season. Use this chart to know when you can expect the first fall frost, and the last spring frost, in your garden or meadow.

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The chart below includes average frost dates for various cities across the U.S. Find the cities near you for good estimate for your frost dates. These dates can vary year by year, usually within about a two-week window.

  • First Fall FrostDate – when to expect the end of the gardening season in Fall
  • Last Spring Frost Date – when to expect the start of the gardening season in Spring

Understanding Your Growing Season: Light Frost vs. “Killing Frost,” “Hard Frost,” or “Freeze”

When late fall arrives, you may start to see frost on the ground when you look out the window in the morning. Depending on how cold it is, you may see some frost before you see a freeze. What’s the difference?

  • A frost (ice crystals forming on surfaces) generally happens when the air temperature is between 36-32 degrees F.
  • A freeze happens when air temperature dips below 32 degrees F. The colder it gets, the more damage you’ll see to annual and perennial plants. A hard freeze is usually between 28-25 degrees F, and a killing freeze is 24 degrees F and below.

In the fall, we’ll ship perennial plants and flower bulbs to you at the right time to plant in your zone!

When planting Wildflower seeds in the fall, plant after a killing freeze. That way, seeds can follow their natural course of germinating and sprouting the following spring.

Please note – the dates below are an average that can be used to estimate the timing of your garden – but it’s important to keep track of your local weather!

City, State First Fall Frost Date Last Spring Frost Date
Atlanta, GA November 18 March 17
Baltimore, MD November 17 March 20
Bismarck, ND September 24 May 12
Boise, ID October 17 April 20
Boston, MA November 8 April 6
Buffalo, NY October 25 May 5
Burlington, VT October 8 May 4
Caribou, ME September 21 May 12
Charleston, SC December 10 February 6
Charleston, WV October 5 April 16
Cheyenne, WY September 27 May 13
Chicago, IL October 28 April 12
Cincinnati, OH October 25 April 17
Cleveland, OH October 20 April 8
Columbia, SC November 20 March 15
Dallax, TX November 30 March 4
Denver, CO October 14 April 30
Detroit, MI October 20 April 18
Houston, TX December 11 February 3
Indianapolis, IN October 27 April 19
Jacksonville, FL December 16 February 6
Kansas City, MO November 2 April 4
Las Vegas, NV December 4 February 6
Miami, FL no frost no frost
Milwaukee, WI October 25 April 22
Minneapolis, MN October 13 April 23
Mobile, AL December 12 February 26
Nashville, TN November 7 April 6
Newark, NJ November 8 April 3
New Orleans, LA December 23 February 4
New York, NY November 12 April 1
Oklahoma City, OK November 7 March 27
Philadelphia, PA November 17 March 31
Phoenix, AZ December 11 January 6
Pittsfield, MA October 4 May 7
Portland, OR December 1 February 26
Providence, RI October 27 April 13
Raleigh, NC November 16 April 1
Richmond, VA November 8 April 4
Sacramento, CA December 10 February 9
Salt Lake City, UT November 6 April 10
Seattle, WA December 1 April 6
St. Louis, MO November 8 April 9
Washington, DC November 17 March 28
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For more details, try looking up your zip code for frost and freeze dates using the lookup tool at Dave’s Garden.

Soil temperature is a helpful piece of information in gardening, too. Wildflower seeds typically germinate when the soil is above 55°F, and many plants will wait for soil temperatures to rise to wake up from winter dormancy. Soil temperature is different than air temperature. Look up your soil temperature with GreenCast.

How to Prepare For Frost

With a killing frost, tender annuals are killed down, and while perennials do better, their leaves, buds, and blooms are usually damaged. Some fall wildflowers are exceptions, with special traits that keep them blooming so they can fulfill their botanical objective of ripening their flowers into seeds. Many sunflowers and asters are in this group, often blooming right through the first frosts.

Does Frost Make the Leaves Turn?

No. The changing color of leaves during fall is a completely separate phenomenon from the falling temperatures. Leaf color change is caused by the shortening days as we go from summer into fall. Interestingly, the brilliant fall color is there all summer, but until fall, it is hidden by the production of (green) chlorophyll. As days shorten in fall, leaves shut down their chlorophyll production, and their real pigments are revealed.