Indoor or Outdoor? How to Choose the Best Way to Start Seeds

Wondering where to start your seeds? This guide shows how I decide what to start indoors and what to sow outside—no guesswork required.

Every gardener runs into this question eventually—should I start my seeds indoors or toss them straight into the dirt? I’ve wrestled with this decision more times than I can count, and I can tell you: getting it right can mean the difference between lush, thriving plants and a sad patch of stunted sprouts.

Some vegetables absolutely need a head start inside, while others prefer to dive right into garden life from day one. Knowing which is which can save you time, frustration, and probably a few seed packets.

Let me walk you through the basics—what should be direct sown, what needs an indoor start, and how your growing zone plays into all of it.

Direct Sowing vs. Starting Seeds Indoors: What’s the Difference?

Before we dig into the details (pun fully intended), let’s go over the main differences between these two methods.

Seedlings growing in a seed-starting tray and seedlings growing in the soil.

What Is Direct Sowing?

Direct sowing means you plant the seeds right into your garden soil, and they stay there for the whole growing season. This is the go-to option for plants that:

Don’t like having their roots disturbed
Prefer cooler soil for sprouting
Grow quickly and don’t need a long season

What Is Indoor Seed Starting?

Starting seeds indoors means planting them in trays or pots—usually on a sunny windowsill or under grow lights—then transplanting them into the garden once the weather warms up. This method works best for:

Crops that need a long growing season to mature
Seeds that are slow to sprout or grow
Plants that need warm soil to germinate

How Your Gardening Zone Changes the Game

Your USDA hardiness zone makes a big difference in whether you should start seeds indoors or direct sow. If you’re in a colder zone (like me here in Maine), your growing season is short and sweet—which means some plants need a head start. Warmer zones get more flexibility.

USDA Plant Hardiness Zone Map with color-coded regions indicating average minimum winter temperatures across the United States.

Here’s a general rule of thumb:

Zones 3–6: Start heat-loving crops like tomatoes and peppers indoors. You can direct sow cool-season champs like peas, radishes, and spinach.
Zones 7–10: Longer seasons mean more crops can be direct sown, but starting seeds indoors can still give you a leg up on succession planting or avoiding intense heat.

Not sure what your zone is or when your last frost usually hits? You can check out my guide to gardening zones and frost dates to get a better sense of timing.

Vegetables That Do Best When Direct Sown

Some veggies are just happier when they skip the transplant process altogether.

Root Vegetables (They Hate Being Moved)

If you mess with their roots, you’ll end up with funky shapes or stunted growth. Direct sow these for the best results:

Carrots
Radishes
Beets
Turnips
Parsnips

Fast-Growing, Cool-Loving Crops

These are great for early spring planting and don’t need a head start:

Lettuce
Spinach
Peas
Arugula

Large-Seeded Crops That Prefer to Stay Put

Big seeds like warm soil and often don’t love being transplanted:

Corn
Beans
Squash (summer and winter)
Cucumbers

Pro Tip: If you’re in a short-season area but still want to grow heat-lovers like squash or cucumbers, try warming the soil with row covers or black plastic mulch. It makes a big difference.

A comparison of vegetables that are typically direct sown (left) vs. started indoors (right), including lettuce, carrots, tomatoes, and peppers. — Some vegetables, like tomatoes and peppers, should be started indoors, while others like spinach and carrots do best when direct sown in the garden.

Vegetables That Should Be Started Indoors

Some plants just do better with a little TLC inside before braving the elements.

Warm-Weather Crops That Need a Jumpstart

These guys won’t do much until the soil is warm, so starting them inside is a must in cooler zones:

Tomatoes
Peppers
Eggplant

Slow-Growing Crops That Need More Time

These take their sweet time, so they benefit from a head start:

Onions (from seed)
Leeks
Celery
Brussels sprouts

Tender Crops That Need Warm Soil

These won’t sprout well if the soil is chilly:

Melons
Basil

Pro Tip: I always start my tomatoes and peppers indoors about 6–8 weeks before my last frost date. I’ve learned the hard way that waiting too long means a much shorter harvest window—especially here in Maine where summer feels like it lasts 10 minutes.

The In-Betweeners: Crops That Can Go Either Way

Some veggies are more flexible and can be started indoors or direct sown, depending on your setup and season length.

Kale
Chard
Broccoli
Cabbage
Pumpkins

If you’re in a colder zone, give broccoli or cabbage a head start indoors. In warmer zones, try direct sowing in early fall for a winter harvest.

A green cabbage growing in the garden, showing healthy, vibrant leaves.

Still Have Questions? Let’s Dig In!

Not always. Some crops—like tomatoes and peppers—really need stable, warm conditions to germinate well. Even in warm zones, you’ll usually get better results by starting them indoors.

Once your seedlings have 2–4 sets of true leaves and the outdoor temps are staying steady, it’s time. Just don’t skip hardening them off—gradually introduce them to outdoor life to avoid shock.

You’ve got options. A cold frame or greenhouse can help, or you can experiment with winter sowing. And hey, there’s no shame in picking up starter plants from a local nursery. Do what works.

I’ve had awesome results using soil blocks instead of traditional seed trays. No plastic cells, no root-bound plants. The roots get “air pruned,” which encourages a strong root system and makes transplanting a breeze. If you want to give them a try, you can grab a soil block maker online—it’s one of those tools that pays for itself pretty quickly if you start a lot of seeds.

Pin this guide to master seed starting like a pro!

Lettuce seedlings growing in a tray, showing early-stage growth for indoor starting.

Choosing between direct sowing and indoor seed starting isn’t a one-size-fits-all thing. It depends on the plant, your growing zone, and what kind of setup you’ve got at home. Most cool-season and fast-growing crops love going straight in the ground, while slow growers and warm-weather lovers need a head start.

And remember—successful seed starting is about more than dropping seeds in soil. Some varieties need specific temps, light levels, or even treatments like scarification or stratification to germinate well. Start simple, build confidence, and grow from there.

So what’s your style—indoor seed starter or direct sower? Drop a comment below and let’s swap notes.