Should You Start Seeds Indoors or Direct Sow?

Not sure whether to direct sow or start seeds indoors? Learn how to decide for each vegetable, based on climate, frost dates, and growing conditions.

Every gardener has faced this dilemma—should I start my seeds indoors or plant them directly into the garden? Making the right choice can mean the difference between strong, thriving plants and stunted growth. Some vegetables demand a head start inside, while others prefer the great outdoors from day one.

Understanding which seeds to direct sow and which to start indoors can help you maximize your harvest. Factors like your gardening zone, frost dates, and plant growth rates all play a role. In this post, I’ll break down the best approach for different vegetable seeds, explain why some plants thrive when started indoors while others don’t, and help you confidently decide what works best for your garden.

Direct Sowing vs. Starting Seeds Indoors: Key Differences

Before we dive into which seeds should go where, let’s cover the basic differences between direct sowing and indoor seed starting.

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

What Is Direct Sowing?

Direct sowing means planting seeds straight into the garden soil, where they will grow until harvest. This method works best for plants that:

Have delicate root systems that don’t transplant well
Prefer cooler temperatures for germination
Grow quickly and don’t need extra time to mature before the season ends

What Is Indoor Seed Starting?

Indoor seed starting means planting seeds in trays or pots inside your home (or in a greenhouse) before transplanting them outdoors. This method is best for:

Plants that need a longer growing season
Vegetables that are slow to germinate or grow
Crops that need warm soil to thrive

How Your Gardening Zone Affects Seed Starting Decisions

Your USDA hardiness zone plays a big role in whether you should start seeds indoors or direct sow. The growing season in colder zones (3-6) is much shorter than in warmer zones (7-10), meaning some plants need extra time to mature before they’re moved outside.

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

Here’s a general rule:

Zones 3-6: Start warm-weather crops (like tomatoes and peppers) indoors to get a head start. Hardy, cool-weather crops (like peas and radishes) can be direct sown.
Zones 7-10: Many crops can be direct sown since the growing season is long. However, starting seeds indoors may still be helpful for succession planting or protecting young plants from extreme heat.

Understanding your gardening zone and frost dates is key to making the right seed-starting decisions. If you’re unsure about your zone or when to expect your last frost, check out my guide to gardening zones and frost dates.

Vegetables That Should Be Direct Sown

Some vegetables don’t tolerate transplanting well or simply grow better when planted directly in the garden.

Root Vegetables

Disturbed roots lead to stunted growth.

Carrots
Radishes
Beets
Turnips
Parsnips

Fast-Growing, Cool-Weather Crops

Can handle early spring planting.

Lettuce
Spinach
Peas
Arugula

Large-Seeded Crops That Prefer Direct Sowing

Corn
Beans
Squash (summer and winter)
Cucumbers

Pro Tip: If you have a short growing season but want to grow direct-sow crops like squash or cucumbers, try using row covers or black plastic mulch to warm the soil faster.

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 crops benefit from a controlled indoor environment before being moved outside.

Warm-Weather Crops That Need a Head Start

Tomatoes
Peppers
Eggplant

Slow-Growing Vegetables That Need Extra Time

Onions (from seed)
Leeks
Celery
Brussels sprouts

Tender Crops That Need Warm Soil to Germinate

Melons
Basil

Pro Tip: I always start tomatoes and peppers indoors about 6-8 weeks before my last frost date. They need warm temperatures to germinate, and giving them a head start ensures a longer harvest window.

When Both Methods Work: Flexible Crops

Some vegetables can be either direct sown or started indoors, depending on your growing season, space, and personal preference.

Kale
Chard
Broccoli
Cabbage
Pumpkins

If you’re in a colder climate, starting broccoli or cabbage indoors will give you a stronger harvest. In warmer zones, they can be direct sown in early fall for a winter crop.

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

Still Have Questions? Let’s Dig In!

Not necessarily. Some crops, like tomatoes and peppers, need a stable environment for germination. Even in warm zones, starting them indoors can lead to stronger plants.

Most seedlings are ready for transplant when they have 2-4 sets of true leaves and outdoor temperatures are consistently warm. Harden them off first by gradually exposing them to outdoor conditions.

Consider using an outdoor cold frame, a greenhouse, or try your hand at winter sowing. You can also buy starter plants from a nursery to save time and effort.

I’ve had great success using soil blocks for indoor seed starting. Unlike traditional seed trays, soil blocks eliminate the need for plastic cells, allowing seedlings to develop stronger root systems with less risk of transplant shock. Since the roots are naturally “air pruned,” they don’t become root-bound, which makes transplanting smoother and healthier for the plant. If you’re interested in trying this method, you can buy soil block making kits—it’s a great investment for any gardener looking to streamline their seed-starting process.

Pin this guide to master seed starting like a pro!

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

Deciding whether to direct sow or start seeds indoors depends on the vegetable, your growing zone, and your available space. Warm-weather crops typically need a head start inside, while cool-season and fast-growing plants do well when direct sown.

Starting seeds successfully takes more than just tossing them in soil and hoping for the best. Some vegetable seeds need specific conditions to sprout, while others might require stratification or scarification to break dormancy. Choosing the right seeds for your growing zone also plays a big role in your success. If you’re new to seed starting, you might want to start with some of the easiest vegetables to grow from seed.

Do you prefer starting seeds indoors or direct sowing? Let me know in the comments which method works best for your garden!