When To Start Seeds Indoors (Easy Printable Sowing Plan)

This indoor seed starting plan is designed for cold climate gardeners in Canada and the U.S. Follow along to time your seeds just right for indoor sowing and outdoor planting.

This is part of a series, Indoor Seed Starting for Beginners | Sow Indoors Grow Outdoors, where I walk you through the process from seed to garden. It’s all the information I wish I had when I was getting started.

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Simple Indoor Seed Starting Plan

The sowing instructions on seed packets tell us how many weeks before our average last frost date seeds should be started indoors. This can range from 3 to 12 weeks or more, depending on the type of plant.

To keep it simple, I created this streamlined sowing system. The seeds are grouped by start times in two-week intervals.

Sowing Groups

You can sow all different seeds using this plan including veggies, herbs, fruits, perennials, and flowering annuals. If you would like to save a copy, it’s available in the Resources section.

Step One

To get started, you need to know your average last frost date.

Step Two

Next, find the date closest to your average last frost date on the chart below.

This tells you the approximate date to start each seed group.

So which group do seeds belong to?

Check your seed packet. For example, if the instructions say to sow indoors 10 weeks before last frost, that’s Group 2.

Don’t worry if you are not exactly on schedule—there’s wiggle room if you need to sow a bit early or later. Just don’t start them way earlier than recommended.

Also keep in mind that different varieties have different timing. For example, one type of broccoli might be in Group 2 but another could be in Group 5. Your seed packet will list the required indoor growing time.

When to Start Seeds Indoors

Here’s an example

My last frost is approximately May 15 which, according to the chart, means seeds that need 12 weeks before last frost (Group 1) should be started on (or around) February 15.

Step Three

• Organize your seeds by their sowing groups (1-5).
• Mark your calendar and sow a new group every two weeks.

Need to get your seeds organized? This show two smart storage systems.

The printable garden planner is designed to help you map our your garden plans and keep notes just how you like them.

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Sample Vegetable Seed Sowing Plan

All seeds are sown indoors unless otherwise noted.

Groups 1 & 2

10-12 Weeks (70-84 Days) Before Last Frost

Very few types of seeds should be started this far ahead, otherwise the plants will get too big before planting time or struggle with indoor growing conditions.

Exceptions include slow-growing cultivars like certain tomatoes, peppers, and onions.

If your indoor temperature stays steady around 70°F (21°C)—give or take 5 degrees or so, most seeds will germinate just fine.

Check your seed packets: you may be surprised by the indoor sowing dates of many crops. There are lots more than I have listed here.

• Broccoli: Santee, Calabrese, Purple Sprouting, Romanesco, Early broccoli
• Celeriac: Giant Prague, Brilliant, Monarch
• Celery: Tall Utah, Golden Self-Blanching, Tango Hybrid
• Eggplant: Black Beauty
• Leeks: Giant Musselburgh, Otina, Splendid
• Onions | Ailsa Craig, Walla Walla, Sweet Spanish, Trident
• Peppers | Habanero, Scotch Bonnet, Anaheim, California Wonder
• Tomatoes | Tiny Tim, Brandywine Red, Red Oxheart, Cherokee Purple

This is also time to start woody herbs from seed including oregano, rosemary, thyme, and sage although growing from cuttings is much faster.

Group 2 & 3

8-10 Weeks (56-70 Days) Before Last Frost

• Artichokes
• Asparagus
• Peppers
• Scallions
• Parsley

Group 4 & 5

4-8 Weeks (28-56 Days) Before Last Frost

This is the busy time for indoor seed starting! Most of what we grow can be started at this time.

A few weeks before last frost your local plant nurseries may also begin selling starter plants. If you get some, be prepared to keep them protected from temperature swings until planting time.

• Basil
• Brussels sprouts
• Broccoli
• Cauliflower
• Cabbage
• Celery
• Celeriac
• Cucumber
• Collards
• Kale
• Melons
• Tomato
• Squash – Summer
• Squash – Winter

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Outdoor Seed Sowing Plan

Direct Sowing Vegetable Seeds

When a seed packet says sow directly, it means you are sowing the seed outdoors, usually in its permanent location as some seeds in this group don’t like being moved.

Root crops like carrots are particularly sensitive to transplanting so avoid this if possible.

Other direct sow seeds are fast-growers that have enough time to mature within our frost-free days so there is no need for indoor sowing.

This has tips on direct sowing outdoors in spring in the weeks leading up to last frost.

Use my notes as a general guide and always check your seed packets for exact outdoor sowing time.

6-8 Weeks Before Last Frost (When Soil is Workable)

Have frost cloths handy in case temperatures dip below 30°F (-1°C).

• Asparagus
• Carrots
• Peas
• Onion
• Radish
• Turnip
• Spinach
• Parsnip

4 Weeks Before Last Frost

Most of these ones like the soil temperature 50°F (10°C) or a bit warmer.

• Arugula
• Brussels sprouts
• Cabbage
• Kohlrabi
• Swiss Chard
• Lettuces
• Leeks
• Mustard
• Potatoes

Some cold-tolerant plants that have several true leaves can now be hardened off and then transplanted outdoors at this time. This includes cabbage, broccoli, Brussels sprouts, kale, lettuce, and kohlrabi.

2 Weeks Before Last Frost

• Beets
• Broad beans
• Pumpkin
• Watermelon

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Sow Directly Outdoors After Last Frost

Once frosts are done, you can begin planting outdoors any starter plants you have—whether you grew them yourself or purchased them—but do it carefully. Warmth lovers like tomatoes are really sensitive to temperature drops.

You will harden off all your plants gradually (gradually get them accustomed to outdoor conditions) and have covers ready after planting in case some unusual weather is forecasted.

And, there are lots of seeds to sow directly in the garden (see suggestions below).

While indoor seed starting provides a good jump start, many of the same plants can be started outdoors when conditions are favorable. Plus, when early crops are done, it’s time to plant new ones in their place (known as “succession planting”).

Again, check your seed packets for specific sowing instructions.

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Resources

Free Printable Seed Sowing Schedule

This seed sowing schedule is free to save to your device.

It’s a PDF document you can view in Adobe Reader and print out if you prefer.

Use it as the starting point and fill in the slots with your seed choices.

I’ve listed the sowing groups and seed examples to get you started.

Buy Seeds

Mail Order Seeds

• SeedsNow (US Shop & Shipping)
• High Mowing Organic Seeds (US Shop & Shipping)
• West Coast Seeds (Canadian Shop | US & CAD Shipping)

I hope this has helped organize your seed starting efforts. The most important part is to just get started, learn as you go, and gradually come up with your own best practices.

~Melissa the Empress of Dirt ♛