When Should I Sow Tomato Seeds?

Since I saved some tomato seeds a couple of weeks ago, I’ve been thinking about what I want to plant next year in the garden….and when to plant what.

I moved here in July, and just started putting things in the ground as soon as I could get around to it, without any real rhyme or reason, just to see what I could get to grow. This was my practice year. Next summer is a chance to do it right!

I don’t have a full list of what I want to grow next year, but I know tomatoes will be on the list. In Seattle, we didn’t sow tomato seeds in the greenhouse until late February, and we usually waited to put them in the ground until early May. The climate is milder here, though, so I imagine I can start tomatoes a bit earlier.

According to garden.org, in my zipcode it looks like I should be starting most spring crops as early as November – even before Thanksgiving!. Tomato seeds can be sown as early as November 25th.

Screenshot of garden.org planting calendar

I am skeptical about this planting calendar. Most sources say to sow tomato seeds indoors 6-8 weeks before your last frost date. My last frost date is Feb 22nd. Counting backwards, I should sow tomato seeds December 28th at the earliest, not November 28th! Garden.org must have done their math wrong…

I turned to the trusty Margaret Roach’s seed starting calculator, which states the same general guideline (sow tomato seeds 6-8 weeks before last frost), and plugged in my quoted last frost date of February 22nd, expecting to get December 28th…. Nope!

November 3rd! That’s crazy!

Some of the dates in Margaret Roach’s calculator are slightly different, but overall, they’re pretty similar to garden.org. Hmmm…..

Screenshot of part of Margaret Roach’s planting calendar for comparison

What is going on? Does it have to do with day length in the middle of winter? I’m not sure. Most people use grow lights nowadays so daylight shouldn’t matter that much. Does anyone have any ideas?

I’ll probably split the difference, and start seeds in mid-December. My fall crops will probably still be in the ground when I start seeds for spring. It’s non-stop gardening here!