Understanding Frost Dates and Knowing When to Seed

Come June, there are hushed whispers floating around. “Do you have tomatoes yet? I heard so-and-so got one last week.” Which then turn into “CRAP, really? I only have flowers!” when the answer is affirmative. Because there seems to be an unspoken contest amongst gardeners, to see who can be the first one with ripe tomatoes. Who got the timing right on planting out in optimum conditions. Because after months of greens, we want color and someone thing new!

the first tomato of 2014, picked June 30, seeded February 24
the first tomato of 2014,  seeded February 24 & picked June 30

Gardening is always one big gamble, and you are betting against Mother Earth. 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 its not warm enough, the plant might just sit there, like a garden statue, not growing and taking up valuable planting real estate. Plant seeds in soil to wet, and they might rot.  If you plant too late, the first fall frost might hit and kill the plant before you could harvest. If it doesn’t receive enough daylight hours, it might stop producing long before you were planning it to.

frost tipped chard

The way to win at this high-stake game is to cross your fingers, hope Mama plays nice, and consult your projected frost dates. There are two frost dates, the first average frost, which happens in Fall, and the last average frost, which happens in Spring. This Spring date is what is used to determine when to start seeds for all the finicky summer veggies we love and crave, like peppers, eggplants, tomatoes, squash and melons.

calendar frost date

Once you know your frost date, you count backwards to determine when you should start your seeds. Tomatoes, for example, are started about 7 weeks before the last frost. Melons, 3 weeks. Johnny’s Select Seeds has an amazing and indispensable chart to help determine the timeline. If someone has an earlier frost date, that means you can start your seeds earlier, leading to planting earlier which means you’ll get fruit earlier. Which is why you may find yourself comparing yourself to the person you saw on Instagram who had ripe fruit IN MAY!

cherry tomatoes

But don’t do it, don’t compare! Everyone’s frost date is different, and even with that you can always take chances. 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.

frost tipped lettuce

Its super easy to find your frost date, just ask the interwebs “last frost date for [enter zip code or city].” 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 she feels most comfortable basing plantings on. I usually seed based on 10% chance, which puts Santa Rosa and the surrounding towns to be around April 10.

IMG_3497

But frost dates aren’t a code, they are simply guidelines. You can experiment, and you can try to push the growing season. Because we’ve had such a warm winter, I feel frost is less likely so I think I will base my calendar off of a date in late March. You can try planting out early by warming the soil with plastic or protecting your plants with cloches or a hoop house. My mom, who grows an amazing garden, lives in Sunset zone 1A, 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!

frost tipped cabbage

Now that you know your frost date, start putting seeding dates on your calendar. You don’t want to miss the first opportunity to get your seeds started! Happy Seeding!


I’m watching it rain right now, and so overjoyed! I hope you are happy with the weather wherever you may be!

Understanding Projected Frost Dates, and how to use them

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6 thoughts on “Understanding Frost Dates and Knowing When to Seed

  1. I think it is a little easier for Northern gardeners to grow tomatoes. Here in Austin there seems to be a tiny window of opportunity between too cold to grow at all and too hot to set fruit. Knowing those dates is pretty important.

  2. Hi Melissa, This is so helpful! I’m planning on planting my first “real” garden this year, and I need all the tips I can get! I’m still figuring out what to grow, but was wondering when to plant tomatoes.

    1. Its one big learning curve, there is lots of figuring out things as I go! I’m planning on seeding tomatoes inside on Feb. 22, then usually after 4-5 weeks, they get transplanted into 4″ pots, then I plant them out in the garden around April 13. If you don’t want to bother with starting your own seeds, Harmony has a great supply of heirlooms, and I think a neighbor got a bunch from Imawilds (spelling? the place on 3rd). I’ll sure I’ll have extras, as well.

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