Seeds to Start Indoors 2–4 Weeks Before Your Last Frost

Learn which seeds to start indoors 2–4 weeks before your last frost date, including fast-growing vegetables that transition quickly to the garden in early spring.

Red and green leaf lettuce seedlings growing in a tray under grow lights indoors.

As planting season approaches, seed starting shifts from long-term planning to short, strategic timing.

The 2–4 weeks before your average last frost date is the final window for starting a small group of fast-growing crops indoors. These plants don’t need much time under lights, but a brief indoor start can give them a head start, especially in cooler climates or gardens with a shorter growing season.

In this guide, you’ll learn which seeds to start indoors during this window and how to decide whether starting indoors or direct sowing makes the most sense for your garden.

Start With Your Average Last Frost Date

As with all seed-starting decisions, timing begins with your average last frost date.

This date tells you when it’s typically safe to plant tender crops outdoors. To find yours, enter your ZIP code at PlantMaps.com or Garden.org, then count backward to determine when to start seeds indoors.

If your frost date is still a few weeks away, go ahead and save this post so it’s ready when the timing is right.

For a step-by-step explanation of frost dates and how to build a planting plan around them, see: How to Create a Seed Starting Schedule Based on Your Last Frost Date.

Seed packets, calendar, and a seed starting schedule laid out on a kitchen table. — Creating a simple seed starting schedule helps you time fast-growing crops so they don’t outgrow their containers.

Why These Seeds Are Started 2–4 Weeks Before Frost

Seeds started during this window grow very quickly and are usually ready for transplanting soon after sprouting.

Crops started indoors 2–4 weeks before frost:

Germinate better under a more controlled environment.
Require only a short time under grow lights.
They are often transplanted outdoors shortly after the last frost.

Many of these crops can also be direct sown outdoors, but starting them indoors can help you get an earlier harvest or give seedlings a better start in cooler spring weather.

Seeds to Start Indoors 2–4 Weeks Before Your Last Frost Date

The following crops are well suited to a short indoor start. They grow quickly and benefit from being transplanted while young.

Vining and Warm-Season Crops to Start Indoors

Many warm-season crops grow rapidly and don’t tolerate cold soil well. A brief indoor start allows them to establish before moving into the garden.

Cucumbers

Cucumbers grow quickly and transplant best when young. Starting them indoors can help them establish fast, giving you earlier fruit, especially in cooler climates.

Summer Squash

Summer squash seedlings grow fast and are ready for transplanting in just a few weeks. Starting them indoors can speed up early harvests.

Winter Squash

Winter squash benefits from a short indoor start, particularly in areas with shorter growing seasons.

Young squash seedlings growing in plastic cups under grow lights indoors. — Squash seedlings develop fast and benefit from a brief indoor start before moving outside once frost danger has passed.

Pumpkins

Pumpkins grow quickly and can be started indoors for an earlier start, but should be transplanted carefully while still small.

Zucchini

Zucchini is fast-growing and easy to start indoors. A brief indoor start helps plants establish quickly once transplanted.

Melons to Start Indoors

Melons love warmth and grow best when planted into warm soil. Starting them indoors gives seedlings a head start while you wait for outdoor conditions to improve.

Cantaloupe

Cantaloupe benefits from a short indoor start, especially in regions where spring soils warm slowly.

Watermelon

Watermelon seedlings grow quickly and should only be started indoors briefly. Transplant them carefully to avoid root disturbance.

Herbs and Greens to Start Indoors

Some herbs and greens grow quickly and can be started indoors during this window if you want an early harvest or need flexibility with spring weather.

Dill

Dill grows quickly and can be started indoors, though many gardeners prefer direct sowing once the soil warms.

Lettuce

Lettuce grows fast and can be started indoors for early transplants, especially in cool spring weather.

Review the Seed Packet Before You Start

Because timing is tight at this stage, your seed packet is especially important.
Before planting, review:

Timing: Recommended sowing time based on frost dates.
Planting Depth: How deep to plant seeds for best germination.
Germination Time: How quickly seeds sprout.
Spacing: Helpful when transplanting seedlings outdoors.

Always follow the seed packet instructions, especially for fast-growing crops.

Tips for Starting Seeds Indoors Successfully

When starting seeds indoors this close to planting time, focus on keeping seedlings compact and healthy:

Provide bright light immediately after germination.
Avoid overwatering.
Harden off plants carefully before moving them outdoors.
Transplant seedlings while they are still young.

Helpful resources:

Can These Seeds Be Started Earlier or Later?

This window is flexible, but timing still matters.

These crops should not be started too early, or they may become overgrown.
Many can be direct sown outdoors once frost danger has passed.
A short indoor start is helpful, but not required.

Choose the method that best fits your space, schedule, and climate.

What to Start Next

As you reach the final weeks before your last frost date, the focus begins to shift from indoor seed starting to outdoor planting.

As you move into the final weeks before your last frost date, seed starting shifts from trays under lights to the garden itself.

If your soil has drained and conditions are improving, this is a good time to begin planting outdoors. Cold-tolerant crops can be sown directly in the garden during this window:

Seeds to Direct Sow 2–4 Weeks Before Your Last Frost (Coming Soon)

At the same time, begin preparing your indoor-grown seedlings for life outdoors. Gradually exposing plants to outdoor conditions helps prevent shock and ensures a smooth transition to the garden:

How to Harden Off Seedlings Before Transplanting

Once your last frost date has passed, you can move fully into warm-season planting. This is when heat-loving crops are ready to be planted directly into the garden:

Seeds to Direct Sow After Your Last Frost (Coming Soon)

This final indoor seed-starting window helps ease the transition from winter planning to spring planting. With just a little preparation now, you’ll be ready to move confidently into the outdoor growing season.

Good planning is key to a successful vegetable garden

Whether you are new to growing your own food or have been growing a vegetable garden for years, you will benefit from some planning each year. You will find everything you need to organize and plan your vegetable garden in my PDF eBook, Grow a Good Life Guide to Planning Your Vegetable Garden.