When Should I Start Tomato Seeds Indoors on the California Coast?
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Mid-February to early March, depending on your specific location. Coastal gardeners start later than you might think because our soil stays cool longer.
The standard advice is to start tomato seeds indoors 6 to 8 weeks before your last frost date. In Santa Cruz, the last frost for coastal areas falls around mid-March, putting your seed-starting window at the end of January to early February. But soil temperature matters more than frost dates for tomatoes. Tomato roots need soil above 60F to grow actively, and coastal soils often do not hit that mark until late April or May. UC Davis's vegetable planting guide recommends waiting to transplant until nighttime air temperatures stay consistently above 50F, which in the fog belt can mean late April or even early May.
So if you start seeds in late January, you may have 10-week-old seedlings waiting on weather that is not ready for them. I've had the best results starting tomato seeds in mid-February for coastal gardens and early February for warmer inland locations like Watsonville or Scotts Valley. That gives you stocky, 6-to-8-week-old transplants right when conditions allow planting out.
Use a heat mat under your seed trays (tomato seeds germinate best at 75F to 85F) and grow lights positioned 2 to 3 inches above the seedlings. A sunny windowsill is not enough on the coast; the low winter light angle produces leggy, weak stems.
This week: Order your tomato seeds now if you haven't already. Choose at least one early variety (Stupice, Early Girl, or Glacier) for the fog belt and one cherry variety (Sungold, Sweet 100) for reliable production.
Our free Seed Starting Guide includes a detailed indoor starting schedule by crop and microclimate. For variety recommendations, check out our Tomato Variety Selector to match varieties to your growing conditions.
Keep Reading
Is January Too Early to Start Seeds Indoors in Coastal California?
What Are the First Five Vegetables a Beginner Should Grow in Santa Cruz?
Where to get seeds: For varieties that do well in our climate, we like Seeds Now, a California company selling non-GMO, open-pollinated, and heirloom seed. (Affiliate link, see our disclosure.)
Starting indoors is a choice, not a rule; here is why you do not have to start seeds indoors for a good harvest.
Frequently Asked Questions
When should I start tomato seeds indoors on the coast?
Mid-February is the sweet spot for coastal gardens, with early February working for warmer inland areas like Watsonville or Scotts Valley. That timing produces stocky six to eight week old transplants right when conditions allow planting out.
Why start later than the usual six to eight weeks before last frost?
Our last frost is around mid-March, but tomato roots need soil above 60 degrees to grow actively, and coastal soils often do not reach that until late April or May. Starting too early just leaves you with overgrown seedlings waiting on cold ground.
What equipment helps coastal seed starting succeed?
A heat mat to hold 75 to 85 degrees speeds germination, and grow lights set 2 to 3 inches above the seedlings prevent legginess, since a windowsill rarely gives enough light here. Choosing an early variety like Stupice or Early Girl plus a cherry type like Sungold improves your odds.
