Last Frost Date: When Is It Time To Plant A Garden In Washington?

SEATTLE — Spring is springing in Western Washington... at least sort of. We've definitely had a few very nice days and the weather is getting warmer, and its almost time to get started on your new garden.

Whether you’re a first-time or experienced gardener, one of the most important dates you need to know as you think about your garden this spring is: the frost date, the average date of the last light freeze in spring.

So when does the danger of frost pass here in Puget Sound? Depends. In Seattle, it already has. According to The Old Farmer’s Almanac, Seattle's final spring frost should have come before the 17th. However, the South Sound should wait just a few more days before planting: in Tacoma, the last spring frost usually happens by March 28.

The growing season is about 220 days long in Washington. Looking ahead to fall, the first frost usually occurs in early-to-mid November.

According to the publication, there’s a 30 percent probability of a frost occurring after November 3, as the date is determined using National Oceanic and Atmospheric historical data from 1981-2010, and is not “set in stone,” The Old Farmer’s Almanac said.

The spring frost date represents the average date of the final “light freeze,” which occurs when the temperature dips between 29 and 32 degrees Fahrenheit. At that temperature, tender plants can be killed.

A “moderate freeze,” between 25 and 28 degrees, is destructive to most plants; and a “severe freeze,” at anything under 24 degrees, can do heavy damage to most garden plants, according to the almanac.

As the pandemic’s third gardening season gets underway, The Old Farmer's Almanac has another tool to help gardeners decide when to plant which crops. Corn, for example, should be planted any time between now and the end of the month.

Here’s a look at other crops, and when the Old Farmer’s Almanac says to begin planting them in Washington:

• Beets: March 2-17
• Cilantro: March 17-31
• Green Beans: March 24-April 14
• Okra: March 31-April 14
• Potatoes: March 9-31

Even before the pandemic, mental health experts pointed to gardening as a way to deal with stress.

Gardening provides physical exercise and promotes healthier eating, but it can also reduce worry among people who consider themselves perfectionists, psychologist Seth Gillihan said.

“Given the lack of control we have, gardening can be a good antidote for perfectionism,” Gillihan wrote in a 2019 Psychology Today blog. “No matter how carefully you plan and execute your garden, there are countless factors you can't predict — invasions by bugs, inclement weather, hungry rodents.”

With so many things out of their control, perfectionism is a waste of time, he said, so gardeners may ask themselves “why bother” trying to be perfect— making it much easier to just go with the flow and accept life as it is.