October 12, 2026

Which survival garden seeds fit your frost-free season

Quick greens, radishes, peas, and bush beans from a survival seed kit will ripen in almost any frost-free season. Winter squash, corn, and melons ripen only where the stretch from last frost to first frost runs well past the days to maturity on the packet. The test takes two numbers: the packet's days to maturity and your yard's frost-free days. Take the second number from your own area's nights, because published frost dates can run weeks too generous.

How to find your frost-free window

A survival kit ships the same variety list to every address. Your season is set by your nights. On a still night, heavy cold air slides down any slope and collects in hollows, because it weighs more than the warmer air above it. A garden in a hollow or at the foot of a slope can frost weeks before the regional date says it should.

In our own garden the published dates give a frost-free window from April 28 to October 22, about 177 days. Our station learned that our garden runs 7°F colder than the forecast. After that offset our window runs May 20 to September 30, about 133 days. That's 44 days, more than six weeks, that a long-season crop can't use.

Our first recorded fall frost last year came on October 3, 19 days ahead of the published date. Why your last frost date is probably wrong covers how those published dates are built.

Without a station, the free microclimate checker compares the nightly lows of nearby home weather stations with the forecast model's lows over recent nights. It returns a range and a median of how much colder or warmer those stations ran, plus a confidence level based on how many stations it found. It reads your area, so it can't see a frost pocket at the bottom of your own slope. If your beds sit lower than the houses around you, expect nights colder than its median.

Quick greens, radishes, and peas

• Frost tolerance. Lettuce, spinach, radishes, and peas handle light frost. In cold weather their cells build up sugars, which lower the freezing point of the sap.
• Season it needs. These are short-season crops you can sow before the last frost and again in late summer. The frost dates don't cap their season.
• In our garden. We sowed peas on March 25, about a month before the published last frost. We direct-seeded radishes on July 9 and lettuce and spinach on July 29 for a fall crop.
• Fits. Every season, including the shortest frost pocket.

Bush beans and summer squash

• Frost tolerance. Both die at the first frost. Their leaves hold a lot of water, and ice forming in the tissue ruptures the cells.
• Season it needs. Both mature quickly once the soil warms. They sit still in cold soil, so an early sowing gains you little.
• In our garden. We direct-seeded zucchini on July 5, well after the last frost. It grew through the hottest stretch of our year, which peaked at 97°F on August 5.
• Fits. Almost every season. Even our measured 133-day window leaves room for a midsummer sowing.

Winter squash, corn, and melons

• Frost tolerance. None. One frost kills the vine, and fruit that hasn't ripened stops developing.
• Season it needs. These need the longest warm run in the kit. They grow by accumulated heat, so a cool summer slows them even when the calendar shows time left.
• In our garden. We transplanted a red kuri squash on June 1 and a watermelon on May 28, both as seedlings. Our garden has banked 1,555 growing degree days (base 50°F) so far this year, and a colder site banks fewer.
• Fits. Long windows, or shorter ones if you start transplants indoors. Corn is the hardest case, because it transplants poorly and kits supply it for direct sowing.

Suppose your kit's winter squash packet lists 110 days to maturity. In our published window that leaves 67 days of slack. In our measured window it leaves 23 days, and one cool stretch in June can use those up. Packet days also assume warm weather, so a cold spring stretches them by an amount no offset predicts.

Which seeds fit your season

Shift your frost dates by your local offset before you count days. A free Siltwell account lets you enter that offset by hand in the garden's microclimate offset setting, and it moves the frost dates the app uses for planning.

• Short or frost-pocket window. Plant the quick greens, radishes, peas, and bush beans. Hold the winter squash and corn seed for a year you can start transplants indoors.
• Middle window. Grow every quick crop, and start winter squash and melons indoors so they go out as seedlings after the last frost.
• Long, warm window. The whole kit fits, corn included, when each packet's days to maturity sits well inside your measured window.

Before you open the kit, write your measured frost-free days on the lid and read every packet against that number. For crops beyond the kit, matching vegetables to your water and frost runs the same test on a wider list.