My first spring in Thunder Bay, I started my tomatoes on March 1st. Same as Grandpa always did back in Iowa. By the time it was safe to plant them out, which up here was June 10th that year, they were four feet of floppy, yellow, root bound sadness. Mark asked if I was growing vines on purpose.
That was the year I learned the most important thing about starting seeds: the calendar doesn’t matter. Your last frost date does.
Find your date first
In central Iowa, the last frost is usually around late April or early May. Outside Thunder Bay it’s closer to early June, and I’ve seen frost on June 12th. That’s a five week difference, which is why my Iowa timing was so wrong.
Look up your town’s average last frost date and write it on a sticky note on the fridge. Then count backwards from it for everything.
What I start, and when
10 to 12 weeks out (early to mid March for me): onions and leeks. They’re so slow. I used to skip these and just buy sets, but growing from seed gives you way more variety. If they flop over, give them a haircut down to about 3 inches. Sounds mean, makes them sturdier.
8 to 10 weeks out (late March): peppers. They love heat and take forever to germinate, so they go on the heat mat. Most of my perennial flowers go in now too.
6 to 8 weeks out (mid April): tomatoes. Not March! Learn from me. Broccoli, cabbage and kale go in at the same time.
3 to 4 weeks out (early May): squash, cucumbers, pumpkins. These grow fast and hate having their roots disturbed, so I start them in bigger pots, usually old yogurt containers with holes poked in the bottom.
Straight in the ground: carrots, beets, radishes, peas, beans, spinach. I’ve tried starting carrots indoors. Don’t. They come out looking like little orange octopuses.
My setup is not fancy
I start everything on a metal shelf in the basement with two cheap LED shop lights hanging from chains so I can raise them as the plants grow. Lights stay about 2 inches above the seedlings, on a timer for 16 hours a day. A sunny window is not enough, no matter how sunny. Ask my first batch of leggy tomatoes.
I use bagged seed starting mix, not garden soil. Garden soil (especially my clay) gets hard as a brick in a cell tray. And I bottom water by pouring water in the tray underneath and letting the cells drink it up, which pretty much solved my overwatering problem.
Don’t skip hardening off
The year after the tomato vine disaster, I did everything right and then killed half my seedlings in one afternoon by putting them straight outside in full sun and Lake Superior wind. They looked like cooked spinach by dinner.
Now I harden off for about 10 days. First day, an hour in the shade. Then a bit longer every day, a bit more sun, until they’re out all day and all night. Annoying? Yes. Worth it? Also yes.
Cheat sheet
| Crop | Start indoors | Leah’s note |
|---|---|---|
| Onions, leeks | 10 to 12 weeks before last frost | Give them haircuts |
| Peppers | 8 to 10 weeks before | Heat mat makes a huge difference |
| Tomatoes | 6 to 8 weeks before | Not March. Seriously. |
| Broccoli, cabbage, kale | 6 to 8 weeks before | Can go out a little before last frost |
| Squash, cukes, pumpkins | 3 to 4 weeks before | Bigger pots, gentle hands |
| Carrots, peas, beans, beets | Direct sow | No octopus carrots |
If you’re new, start with just tomatoes, peppers and a few flowers your first year. You’ll figure out your rhythm. And if you’re gardening somewhere cold, ignore anyone online telling you to start tomatoes in February. Including your grandpa. Sorry, Grandpa.
