How Do I Know When to Start My Seeds?

Every spring I do the same thing: I pick up a seed packet, stare at it like it owes me money, and think… okay, but when do I actually start these?

The good news is this: once you learn the one basic trick, the whole seed-starting thing gets way less mysterious.

That trick is to stop thinking “what month should I start seeds?” and start thinking: what am I counting backward from?

For most vegetables, you’re counting backward from your average last frost date. For a lot of native plants, you’re counting backward from a different thing entirely: winter.

Let me explain how I do it in real life, without pretending I’m a seed wizard.

Veggies: the seed packet is usually telling you exactly what to do

Most veggie seed packets have one line that matters more than all the others. It usually looks like this:

“Start indoors 6–8 weeks before last frost.”

When I finally understood that line, everything clicked. Because it’s not asking you to guess. It’s giving you a simple recipe:

Find your last frost date → count backward 6–8 weeks → start seeds in that window.

That’s it. That’s the whole plan.

So if your last frost date is somewhere around mid-May (just as an example), then six to eight weeks earlier lands you somewhere around mid-to-late March. I’ll literally take a calendar (digital or paper), count backward, and circle a weekend that looks realistic for my life. Not “the perfect date,” just “a date I’ll actually do it.”

Sometimes the packet says “direct sow after last frost.” That’s also wonderfully straightforward. It means the plant would rather you skip the indoor phase and put the seed right outside once frost risk is mostly done. If you’ve ever tried transplanting something that immediately throws a tantrum, this is usually why. Some plants just want to be planted and left alone.

What about DTM? (Days to Maturity / Days to Harvest)

DTM is the part that makes people feel like they’re doing gardening wrong.

You’ll see something like “90 days” and think, “From when? From today? From seed? From sprout? From the moment I made eye contact with it?”

Here’s the simplest way I’ve learned to think about DTM: it’s not a seed-starting instruction. It’s a harvest estimate.

And it’s usually either counting from when you plant outside (especially for things you transplant, like tomatoes and peppers), or from when the plant is up and growing (especially for direct-sown crops). Different seed companies count it differently, which is why it can feel slippery.

So I use DTM as a rough heads-up like, “This is a longer-season crop,” or “This should be pretty quick,” not as a stopwatch. If your tomato says 75 days and it’s not producing on day 76, you didn’t fail. The tomato is simply being a tomato.

When the seed packet is vague (or missing): how I look it up online

Sometimes the packet is great. Sometimes it’s basically a tiny piece of paper that says “plant seed… somewhere.”

When that happens, I do a quick search, but I try to search in a way that gives me answers that are actually usable. I don’t search “when do I start kale” because that gets you everything from blog posts to chaos. I search more like:

“kale start indoors weeks before last frost”
or
“kale direct sow last frost”

Because the “weeks before last frost” language is what you’re trying to find. If a few sources disagree, I don’t spiral — I pick the middle recommendation and move on. Gardening has enough drama already. I don’t need my browser joining in.

Native plants: the seed packet might not talk about dates at all

Native plant seeds are the part where veggie gardeners suddenly feel like they’ve been dropped into a different game.

Because with native plants, a lot of seeds are designed to not sprout at the first sign of warmth. In nature, that would be a disaster. So many native species need a winter cue to wake up.

The word you’ll see a lot is stratification — which sounds intense, but usually means some version of: “this seed needs a cold, moist period before it will germinate.”

So instead of asking, “How many weeks before frost?” you’re often asking, “Does this seed need a cold period, and how long?”

When I’m not sure, I look it up using the plant’s scientific name if I have it (because common names can be… a mess). Searches that usually get me what I need are:

“[scientific name] cold stratification days”
or
“[scientific name] germination requirements”
or
“[common name] winter sowing”

If I find that the seed needs, say, 30–60 days of cold moist stratification, then I know my timeline isn’t really about spring — it’s about making sure the seed gets its “winter time,” either outdoors (winter sowing) or in a fridge (controlled stratification), and then sowing after that’s done.

And I’ll be honest: for natives, I’ve found it’s better to aim for “good enough and consistent” than “perfect.” A lot of native seeds will sprout on their own schedule anyway. They don’t read my calendar. They’re not checking my spreadsheets. They’re just out here living.

The way I keep this from becoming complicated

If I’m doing veggies: I anchor to last frost and count backwards based on the packet. If I’m doing natives: I anchor to dormancy/stratification and figure out what winter cue they need.

And if I’m feeling overwhelmed, I do the simplest possible thing: I pick one veggie and one native plant to learn with. Because doing it once teaches you more than reading fifty posts about doing it “correctly.”

Seed-starting is supposed to be encouraging and fun. If it starts feeling like homework, it’s time to simplify.