When is the best time to start tomatoes from seed?

This has been an ongoing debate I've had with other gardeners. Debates like this are pretty common, and because so many of them come down to preferences alone there's often no right or wrong about them.

But there is right and wrong with cause and effect. In the case of when to start tomatoes from seed, the cause is the day a seed is put into soil. The effect, in my mind, is how soon you get a ripe fruit.

Because of some embarrassing failures earlier this year, I have some reliable data points that give me some answers about just when to start those tomato seeds. My initial idea was that the best time to start them was late January. The tomato plants in my garden right now show that that's not necessarily the case.

Failures Starting Tomato Seeds in 2023

My plan this year was to pre-sprout tomato seeds in late January. Last year, this worked out great. I had ripe tomatoes by early June. This success convinced me that late January is the best time to start tomatoes from seed in Vacaville. Plus, general recommendations are to start tomato seeds six to eight weeks before planting, which in Vacaville is around February 4 to plant on April 1. 

What I had conveniently forgotten was that in February last year we had a sudden heat wave of 90+ degrees for about a week. I had been growing healthy starts in clear plastic bins that work just like cold frames, and it was a few days before I took the tops off to let the hot air out. In short, about half of my healthy seedlings died.

I ended up starting the whole process again from late February through March. I got the surviving tomatoes planted and by June, when the first fruits ripened, I forgot the whole debacle.

This year I had another disaster that happened even earlier, and by my very own hand. My method with tomato seeds has been to pre-sprout them in wet napkins in plastic sandwich bags on a heating mat. As soon as a root emerges, the seeds go into a labeled pot outside in my makeshift cold frame.

What went wrong this year was that the heating mat where I pre-sprouted tomato seeds created such a hot environment that I killed nearly all of them. Out of the far-too-many varieties I attempted to sprout this way in January, maybe four plants—only four—survived.

So I started the whole process again in February. And again in March, when I finally realized my error when I putting a refrigerator magnet thermometer in the pile to find a temperature of over 100F.

All of this led me to an unexpected experiment to see whether nearly two months, from late January to mid-March, made any difference in when I get ripe tomatoes to eat.

Hardy Tomatoes in Spring

In a lot of ways, gardening is really about temperature and sunlight. The more of both—to a point—makes a plant grow faster. There are also a variety's genetics and general hardiness and habit to consider, but in general heat and sunlight are co-equal kings when it comes to how fast a plant will grow.

With tomatoes, how deep they're planted also makes a difference, since any stem that gets buried will push out additional roots. So when I prune side shoots from a hardy plant, I can root every one of them as cuttings and have new plants that will grow fast.

From the time I planted the first round of tomato seedlings in April, I've been watching closely how quickly they grow. I staggered the planting. The January survivors went in first, and the late-March re-dos went in a few weeks later.

Immediately I was impressed with a variety I received as part of a trial through Seed Link. I signed up to trial a total of six varieties of berry tomatoes this year, and it turns out I got one incredibly hardy variety called “Perfection in Pink.” This thing is a beast. It grew faster than even the beastly Cherokee Chocolate variety I'm also growing for the first time, and it's put out far more fruit clusters than even my beloved Brad's Atomic Grape from pre-sprouted seed I potted on March 25.

Ripe Tomatoes in June and Plans for Next Year

On June 14^th, I tasted my first ripe tomato, and—surprise, surprise—it came from the Perfection in Pink that is one of the lone survivors of that disastrous January seed massacre. But taking a look at the row of plants, the others, even the ones started two months later, aren't so far behind. In terms of height, the Brad's Atomic Grape plants have about caught up and the fruits look pretty close to showing color.

In the end, it probably doesn't matter whether you start tomato seeds in January or March. In a month, when I have more tomatoes than our small family can eat, I'll probably get that familiar garden amnesia, that forgetfulness about the season's failures, all over again.

Next year, I'll probably start tomatoes early again but not for the same reasons. For two years, starting them early worked as a kind of hedge against the inevitable disaster. Because I had so many chances to start over, both seasons ended up great. I had more chances to make mistakes and (hopefully) to learn from them.