When Frost Danger Passes In Boulder, Making Gardening Safe

BOULDER, CO — The right time to start planting seeds outside varies by year, and even more so by region. But an Old Farmer’s Almanac tool can help gardeners in Boulder plan ahead by finding the typical date of the final spring frost.

The average final spring frost date in Boulder is May 9. This opens up a 144-day growing season, as the typical first frost date in the fall is Oct 1.

There’s a 30 percent probability of frost occurring after May 9, 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.

May 9 represents the average date of the final “light freeze” in Boulder. A “light freeze,” according to the almanac, occurs when the temperature dips between 29 and 32 degrees Fahrenheit, at which point tender plants can be killed. A “moderate freeze,” between 25 and 28 degrees, is destructive to most vegetation, 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 second gardening season gets underway in Boulder, the Old Farmer's Almanac has another tool to help gardeners decide when to plant which crops.

In Boulder, the tool shows it’s usually best to start planting these seedlings or transplants on the following dates:

• Basil: Between May 9 and May 30
• Bell peppers: Between May 16 and May 30
• Cucumbers: Between May 23 and June 6
• Kale: Plant as soon as possible, up to May 2
• Lettuce: Plant as soon as possible, up to May 23
• Oregano: Between May 11 and June 1
• Rosemary: Between May 18 and June 8
• Sage: Between May 9 and May 30
• Thyme: Between May 9 and June 30
• Tomatoes: Between May 16 and June 6
• Zucchini: Between May 23 and June 6

You can look up when to plant other crops here in the Old Farmer’s Almanac calendar — just type in your ZIP code or city.

Don't miss the latest news updates in Boulder: Free Boulder Patch Newsletters and Email Alerts | Facebook | Twitter

The 2021 gardening season is expected to be busy, just like the 2020 season was due to the coronavirus pandemic and related shutdown orders. The pandemic led to a “global gardening boom,” according to a 2020 report from Agriculture Week, as seed companies saw unprecedented interest.

The Burpee Seed Co. sold more seeds last March, when the pandemic began, than any other month in their 144-year history, Agriculture Week reported, and Johnny’s Selected Seed notched a 270 percent increase in sales during the 2020 gardening season.

The brisk seed sales don’t just reflect an interest in a pastime that makes social distancing easy. Experts say gardening is therapeutic.

“There are certain very stabilizing forces in gardening that can ground us when we are feeling shaky, uncertain and terrified,” Rutgers University professor Joel Flagler told Agriculture Week. “It’s these predictable outcomes and predictable rhythms of the garden that are very comforting right now.”

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.