Gardening is always one big gamble, and you are betting against Mother Earth. The secret to having the best odds is to understand your frost dates.
Some plants would grow no matter what, but many of them are picky, like Goldilocks, and will only grow if conditions are just right. Sow seeds or set out transplants too early and you run the risk of them getting hit by frost and melting away. If it’s not warm enough, the plant might just sit there, like a garden statue, not growing and taking up valuable planting real estate. If you plant too late, it might be too hot and your plants will bake, shrivel and die. Or, the first fall frost might hit and kill the plant before you could harvest. Some crops can take light frost and some actually improve with some chill, but many can’t survive the lower temperatures.
In order to avoid these tragedies, it is crucial that gardeners understand their frost dates. These important dates give guidelines on the best times to sow seeds and transplant starts. If you’ve ever found yourself asking: “when do I plant peas/lettuce/tomatoes/beans/winter squash/etc. ? “, read on.
There are two dates to consider: average last frost date, and average first frost date.
Last frost date is the date to look at for spring planting and signals the most likely date that you won’t get any more frost in you garden. Any time after this is usually safe for your plants that are frost tender, meaning they can’t survive frost and will die or be damaged. Most summer veggies are frost tender, like melons, tomatoes and squash, so they need to be planted AFTER that last frost date.
For spring vegetables, like lettuce and peas, this date is used to count backward to know when to sow so the crop will be ready before it gets too hot.
You use this date as a guideline on when to plant these types of vegetables outside, or you can work backwards and start inside. For example, tomatoes take about 7-8 weeks to sprout and reach a transplantable size. My average last frost is April 10th, so I count back 7 weeks and sow inside around February 20th. I plant them outside one week after the last frost date, around April 17th.
First frost date is the date to look at for fall planting and signals the most likely date that frost will arrive in your garden. Many of the summer veggies, like tomatoes or squash, will die once hit, or the produce left on the vines will seriously degrade in quality. You want to make sure you have harvested your crop BEFORE the first frost.
This frost date also marks a point where you can count backwards to know when to plant your fall and winter crops, like brassicas and roots, which would otherwise struggle in the heat of summer.
Even if you live in a climate that doesn’t have hard freezes, first frost dates are important. The shorter daylight hours means plants grow very slowly, so I like to have crops well established before winter comes.
For example, my first frost date is November 5th. Beets should be sown about 6-8 weeks before the first frost, so I’ll make sowings at the end of September.
How to Find Your Frost Date:
Its super easy to find your frost date, just ask the interwebs “last/first frost date for [enter zip code or city].” Chances of frost is looked at in percentages: there is a 90% chance there will still be frost, a 50% chance, a 10% chance, etc. In the game of gardening and frost, the lower your odds, the better. And because this is nature we are talking about, nothing is ever for certain. Some sources, like Burpee’s Seeds or the Old Farmers Almanac, will give you only one date, and I avoid those. They are reporting a 50% chance date, and I don’t like to play with that much chance of frost.
My favorite sources to determine data is either NOAA or Dave’s Garden, both which give a wide range of dates, letting the gardener determine what they feels most comfortable basing plantings on. I usually seed based on the 10% chance date.
Things to Consider Regarding Frost Dates:
Frost dates, aren’t a code, they are simply guidelines. You can experiment and you can push the growing season longer in either direction. You can try planting out early by warming the soil with plastic and protecting your plants with cloches, frost blanket, or a hoop house. Particularly if you lean towards using a date that has a higher percentage, it’s a good idea to have frost blankets ready.
You can also get creative with growing indoors and in cold frames or greenhouses. My mom, who grows an amazing garden near the Oregon/California border, lives in Sunset zone 1A (USDA zone 6) and has a last frost date of June 7. This makes her growing season only a few months, which doesn’t work for tomatoes. So she starts seeds inside the first week of February, progressively transplants them into larger pots, then when they start to flower in June, she takes them outside and plants them in the garden. She gets hundreds of pounds of tomatoes. So anything is possible!
Everyone had different frost dates depending on the climate and terrain where you live. Especially in the age of everyone being connected, its easy to compare yourselves to other gardeners. So if you see someone on Instagram posting pictures of tomatoes ripe in May, and your plants haven’t even started to flower, know you’re not behind and you’re not a poor gardener: you just have a different frost date!
If you ever find yourself wondering exactly when you’re supposed to plant your broccoli, peas, etc., my new Garden Planning Worksheets are just for you! They are customizable to any growing zone and help you determine exactly when to plant for both spring and fall. Get your free copy here!
Want more information and ideas on how to plan your edible garden? Check out this post: Garden Planning: The Steps I Take for My Homestead