What Seeds To Start Indoors (10 Plants To Start Early Indoors) | GreenUpSide (2024)

Do you live in a cold climate where frost lingers late in the spring and arrives early in the fall? If so, it might make sense to start seeds indoors – but some crops transplant well, and others don’t.

So, what seeds do you start indoors? Seeds to start indoors include: broccoli, cabbage, cauliflower, eggplant, kale, lettuce, okra, peppers, Swiss chard, and tomatoes. In warm climates, you can direct sow some of these seeds right into the garden. In cold climates, your best bet is to start these seeds indoors and transplant later.

Of course, the days to germination, planting time, and transplanting time will vary depending on the crops you choose to grow. Even different varieties of the same crop can show some differences in how long they take to mature.

In this article, we’ll take a closer look at these 10 crops whose seeds you should start indoors.

Let’s get started.

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What Seeds To Start Indoors

Here are 10 common garden crops whose seeds you can start early indoors:

• Broccoli
• Cabbage
• Cauliflower
• Eggplant
• Kale
• Lettuce
• Okra
• Peppers
• Swiss Chard
• Tomatoes

The following table summarizes these 10 crops and their seed germination time, seed starting dates, and transplant dates. Dates are based on weeks before (BLF) or after (ALF) the last frost date (which you can find by zip code from the Old Farmer’s Almanac).

Let’s take a closer look at each of these crops – we’ll start off with broccoli.

Broccoli

Broccoli is a cool weather crop that begins to bolt when summer heat and longer days arrive. Broccoli seeds will last 3 to 4 years before you see reduced viability and germination rate.

Plant broccoli seeds indoors (1/2 inch deep) 7 weeks before the last spring frost date. Broccoli seeds will germinate in 4 to 20 days under ideal conditions (moist soil at 60 to 85 degrees Fahrenheit or 16 to 29 degrees Celsius).

After germination, give broccoli plants 3 to 4 weeks to grow before transplanting into the garden. Transplant 2 weeks before the last spring frost date, leaving 8 to 12 inches between plants and 12 to 30 inches between rows.

A few broccoli varieties from Johnny’s Selected Seeds include:

• Belstar – this hybrid broccoli variety is USDA certified organic and produces medium green heads of medium size. It matures 65 days after transplant.
• Marathon – this hybrid broccoli variety tolerates cold and can overwinter. It matures 68 days after transplant.
• Monty – this hybrid broccoli variety tolerates heat and produces large, bright green heads. It matures 56 days after transplant.

You can learn more about when broccoli produces heads in my article here.

You can learn more about growing broccoli from Clemson University.

Cabbage

Cabbage is a cool weather crop that produces round heads and is related to broccoli. Cabbage seeds will last 3 to 4 years before you see reduced viability and germination rate.

Plant cabbage seeds indoors (½ inch deep) 9 weeks before the last spring frost date. Cabbage seeds will germinate in 4 to 9 days under ideal conditions (moist soil at 60 to 85 degrees Fahrenheit or 16 to 29 degrees Celsius).

After germination, give cabbage plants 3 to 4 weeks to grow before transplanting into the garden. Transplant 4 weeks before the last spring frost date, leaving 18 inches between plants and 24 to 30 inches between rows.

A few cabbage varieties from Johnny’s Selected Seeds include:

• Merlot – this hybrid cabbage variety produces purplish red heads with long leaves. It matures 60 days after transplant.
• Omero – this hybrid cabbage variety produces 3 pound purplish-red heads. It matures 73 days after transplant.
• Tiara – this hybrid mini cabbage variety produces 1 to 2 pound green heads. It matures 63 days after transplant.

You can learn more about growing cabbage from the University of Minnesota Extension.

Cauliflower

Cauliflower is a cool weather crop that produces what looks like white broccoli (like cabbage, it is also related to broccoli). Cauliflower seeds will last 3 to 4 years before you see reduced viability and germination rate.

Plant cauliflower seeds indoors (½ inch deep) 9 weeks before the last spring frost date. Cauliflower seeds will germinate in 5 to 10 days under ideal conditions (moist soil at 60 to 85 degrees Fahrenheit or 16 to 29 degrees Celsius).

After germination, give cauliflower plants 3 to 4 weeks to grow before transplanting into the garden. Transplant 4 weeks before the last spring frost date, leaving 12 to 18 inches between plants and 24 to 36 inches between rows.

A few cauliflower varieties from Johnny’s Selected Seeds include:

• Amazing – this open pollinated cauliflower variety tolerates both heat and cold, producing white heads. It matures 68 days after transplant.
• Cheddar – this hybrid cauliflower variety produces orange heads. It matures 58 days after transplant.
• Lavender – this hybrid cauliflower variety produces light purple heads. It matures 70 days after transplant.

You can learn more about growing cauliflower from the Utah State University Extension.

Eggplant

Eggplant is a warm weather crop that produces what looks like large dark purple eggs (it is a member of the nightshade family, along with tomatoes and peppers). Eggplant seeds will last 3 to 4 years before you see reduced viability and germination rate.

Plant eggplant seeds indoors (1/4 inch deep) 4 to 6 weeks before the last spring frost date. Eggplant seeds will germinate in 5 to 8 days under ideal conditions (moist soil at 75 to 85 degrees Fahrenheit or 24 to 29 degrees Celsius).

After germination, give eggplant plants 7 to 9 weeks to grow before transplanting into the garden. Transplant 4 weeks after the last spring frost date, leaving 18 inches between plants and 30 to 36 inches between rows.

A few eggplant varieties from Johnny’s Selected Seeds include:

• Aretussa – this hybrid eggplant variety produces cylindrical white fruit that is 6 to 8 inches long. It matures 60 days after transplant.
• Patio Baby – this hybrid eggplant variety grows well in containers (on your patio!) and produces small purple fruit that is 2 to 3 inches long. It matures 50 days after transplant.
• Traviata – this hybrid eggplant variety produces glossy black bell-shaped fruit that is 5.5 to 6.5 inches long. It matures 70 days after transplant.

You can learn more about growing eggplant from the University of Minnesota Extension.

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Kale

Kale is a cool weather crop that produces what looks like large green leaves with ridges or wrinkles. Kale seeds will last 3 to 4 years before you see reduced viability and germination rate.

Plant kale seeds indoors (1/4 inch deep) 10 weeks before the last spring frost date. Kale seeds will germinate in 6 to 10 days under ideal conditions (moist soil at 45 to 85 degrees Fahrenheit or 7 to 29 degrees Celsius).

After germination, give kale plants 5 weeks to grow before transplanting into the garden. Transplant 4 weeks before the last spring frost date, leaving 12 inches between plants and 24 to 36 inches between rows.

A few kale varieties from Johnny’s Selected Seeds include:

• Oldenbor – this hybrid kale variety produces curly medium-green leaves. It matures 60 days after transplant.
• Redbor – this hybrid kale variety produces frilly purple leaves. It matures 55 days after transplant.
• Siberian – this open pollinated kale variety produces curly green leaves. It matures 50 days after transplant (25 days for baby leaves).

You can learn more about growing kale from the North Carolina State University Extension.

Lettuce

Lettuce is a cool weather crop that produces leaves that can be smooth, ruffled, or with interesting patterns on the edges. Lettuce seeds will only last 1 year before you see reduced viability and germination rate.

Plant lettuce seeds indoors (1/4 inch deep) 5 weeks before the last spring frost date. Lettuce seeds will germinate in 2 to 4 days under ideal conditions (moist soil at 60 to 75 degrees Fahrenheit or 16 to 24 degrees Celsius).

After germination, give lettuce plants 2 to 3 weeks to grow before transplanting into the garden. Transplant 2 weeks before the last spring frost date, leaving 4 to 6 inches between plants (leaf lettuce) and 6 to 8 inches between plants (butterhead lettuce), with 12 to 18 inches between rows.

A few lettuce varieties from Johnny’s Selected Seeds include:

• Cherokee – this open pollinated lettuce variety resists bolting in heat and produces dark red leaves. It matures 48 days after transplant.
• Salinova – this open pollinated lettuce variety resists bolting and produces small, long, bright green leaves. It matures 45 days after transplant.
• Tendita – this open pollinated lettuce variety resists bolting in heat and produces dark red leaves. It matures 48 days after transplant.

You can learn more about growing lettuce from the University of Illinois Extension.

Okra

Okra is a warm weather crop that produces pods that look like long peppers. Okra seeds will only last 2 years before you see reduced viability and germination rate.

Plant okra seeds indoors (1inch deep) 1 week after the last spring frost date. Okra seeds will germinate in 6 to 7 days under ideal conditions (moist soil at 85 to 95 degrees Fahrenheit or 29 to 35 degrees Celsius).

After germination, give okra plants 3 weeks to grow before transplanting into the garden. Transplant 4 weeks after the last spring frost date, leaving 18 to 24 inches between plants with 36 inches between rows.

A few okra varieties from Johnny’s Selected Seeds include:

• Carmine Splendor – this hybrid okra variety produces red pods in mid to late summer. It matures 51 days after planting.
• Clemson Spineless – this open pollinated okra variety produces green pods and edible cream-colored flowers. It matures 60 days after planting.
• Jambalaya – this hybrid okra variety produces dark green pods and edible cream-colored flowers. It matures 50 days after planting.

You can learn more about growing okra from the University of Georgia Extension.

Peppers

Pepper is a warm weather crop that produces leaves that can be smooth, ruffled, or with interesting patterns on the edges. Pepper seeds will last 3 to 4 years before you see reduced viability and germination rate.

Plant pepper seeds indoors (1/4 inch deep) 4 weeks before the last spring frost date. Pepper seeds will germinate in 7 to 14 days under ideal conditions (moist soil at 65 to 75 degrees Fahrenheit or 18 to 24 degrees Celsius).

After germination, give pepper plants 6 to 7 weeks to grow before transplanting into the garden. Transplant 4 weeks after the last spring frost date, leaving 18 inches between plants, with 30 to 36 inches between rows.

A few pepper varieties from Johnny’s Selected Seeds include:

• Islander – this hybrid pepper variety produces purple peppers which later mature to dark red. It matures 56 days after transplant (purple/lavender) or 81 days for deep red peppers.
• Olympus – this hybrid pepper variety produces green peppers which later mature to red. It matures 65 days after transplant (green) or 85 days for red peppers.
• Snowball – this hybrid pepper variety produces ivory white peppers which later mature to yellow. It matures 65 days after transplant (ivory white) or 85 days for golden yellow peppers.

You can learn more about growing peppers from the Penn State University Extension.

Swiss Chard

Swiss chard is a cool weather crop that produces green leaves with red veins and ridges (good for salad or soup!) Swiss chard seeds will only last 2 years before you see reduced viability and germination rate.

Plant Swiss chard seeds indoors (1/4 inch deep) 4 weeks before the last spring frost date. Swiss chard seeds will germinate in 5 to 21 days under ideal conditions (moist soil at 50 to 85 degrees Fahrenheit or 10 to 29 degrees Celsius).

After germination, give Swiss chard plants 1 to 3 weeks to grow before transplanting into the garden. Transplant on or after the last spring frost date, leaving 4 to 6 inches between plants, with 18 to 30 inches between rows.

A few Swiss chard varieties from Johnny’s Selected Seeds include:

• Bright Yellow – this open pollinated Swiss chard variety produces yellow stalks with deep green leaves. It matures 57 days after transplant (bunching leaves) or 28 days for baby leaves.
• Fordhook – this open pollinated Swiss chard variety is USDA certified organic and produces white stalks with medium green leaves. It matures 50 days after transplant (bunching leaves) or 25 days for baby leaves.
• Rhubarb Supreme – this open pollinated Swiss chard variety is USDA certified organic and produces red stalks with deep green leaves. It matures 60 days after transplant.

You can learn more about growing Swiss chard from the University of Minnesota Extension.

Tomatoes

Tomato is a warm weather crop that produces fruit that is often red, but also comes in yellow, orange, green, blue, purple, black, or white colors! Tomato seeds will last 3 to 4 years before you see reduced viability and germination rate.

Plant tomato seeds indoors (1/4 inch deep) 4 weeks before the last spring frost date. Tomato seeds will germinate in 6 to 8 days under ideal conditions (moist soil at 65 to 85 degrees Fahrenheit or 18 to 29 degrees Celsius).

After germination, give tomato plants 7 weeks to grow before transplanting into the garden. Transplant 4 weeks after the last spring frost date, leaving 18 to 24 inches between plants, with 48 to 60 inches between rows.

A few tomato varieties from Johnny’s Selected Seeds include:

• Brandywine – this indeterminate, open pollinated tomato variety is USDA certified organic and produces large (over 1 pound) tomatoes with deep pink to red skin. It matures 78 days after transplant.
• Bronze Torch – this indeterminate, hybrid tomato variety produces small (1.5 ounce) tomatoes with brick red skin and bronze-green stripes. It matures 65 days after transplant.
• Sungold – this indeterminate, hybrid tomato variety produces small (15 to 20 gram) tomatoes with tangerine-orange skin. It matures 57 days after transplant.

You can learn more about growing tomatoes from the Oregon State University Extension.

Conclusion

Now you know which seeds to start indoors. The 10 crops on this list should give you a good start if you want to get ahead on planting and extending the season in a cold climate.

If you need to buy seeds, you can explore the possibilities here.

You can learn about seed starting mix (and how to make it) here.

To get started with growing seeds indoors, you might want to check out my article on seed trays.

You can find answers to some common questions about seed trays here.

You might also want to check out my article on the best vegetables to grow indoors.

You can learn some easy ways to sow small seeds here.

I hope you found this article helpful. If so, please share it with someone who can use the information.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here. Enjoy!

~Jonathon