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Home » Learn How To Start Seeds Indoors (What, When, Why & How)

Learn How To Start Seeds Indoors (What, When, Why & How)

Posted April 17, 2020
in Grow

There are two main reasons to start seeds indoors: to extend your growing season and for quality control. Learn the basics of how to start seeds indoors with this helpful step-by-step guide (with video).

Many people wonder whether or not they should start their garden seeds indoors, which seeds should be started indoors, when to start seeds indoors and finally, how to start seeds indoors.

But before you get too focused on starting seeds, we think every gardener (whether new or seasoned) should first read about the 10 most common gardening mistakes any how to choose the right seeds for your garden.

Then, if you haven’t purchased your seeds yet, we recommend Seeds for Generations for some great heirloom seed varieties!

There are two main reasons to start seeds indoors:

Season Extension
Quality Control

Extending the Growing Season

In many areas, extending the growing season is necessary to allow certain crops to get enough time to fully produce. This is usually the case in colder climates and for certain crops that have a longer production time such as tomatoes, peppers, cucumbers, and melons.

This is exactly why we also grow these plants inside a hoop house (learn how to build a hoop house – also known as a tomato trellis or bean tunnel). You can also watch this video or read how to plant tomato plants, cucumbers and peppers properly here.

Growing seeds indoors can also be used in mid-summer when the soil and weather are too hot to germinate crops. We do this with brassicas and other plants that we want to last into fall. We’ll start them indoors midsummer, then transplant them once the weather isn’t so hot.

Controlling the Quality

By starting your seeds indoors you can control the environment which means you can control the outcome with much more accuracy.

Once you learn how to grow seeds indoors you can control the temperature, the light exposure, and even the moisture level.

With all this control, you’ll yield a much higher germination rate, which in turn saves you money because you don’t have to buy as many seeds to get the yield you want.

When To Plant Seedlings Outdoors

When should you transplant your seedlings outdoors? This is our favorite answer, IT DEPENDS!

Transplant dates will vary based on where you live (and the average first and last frost dates), what you’re growing, when you’d like to harvest, and the size of your seed starting tray.

Know Your Last Frost Date in Spring

If you’re wanting to get your starts in the ground as early as possible, you’ll need to know your last frost date in the spring. It’s important to know this date before starting your seeds indoors because seeds have a specific timeframe until production.

Know Your First Frost Date in Fall

If you’re wanting to extend your harvest into the fall, you’ll want to know when your first frost date is in the fall. Then, you’ll need to look at the calendar and do the math backward to ensure you give your crops enough time for production and harvest before that frost date. (This is assuming the crops cannot winter over.)

Know What You’re Planting

Before knowing HOW to grow plants indoors, you should have an idea of WHAT you want to grow. Find a reputable seed company and grab their catalog. Be sure to use a trusted source – we share our favorite seed companies in this post.

Each plant will have a different germination time (how long it takes for the seeds to sprout) and time to harvest. Working backward you’re going to want to come up with a plan on when to start each plant indoors.

A man holding up a Clyde's Garden Planner.

Get a Garden Planner

Our favorite tool for planning when to start seeds indoors is to use a garden planner. We love Clyde’s Garden Planner and it’s so helpful to know exactly when to start your seeds indoors and when to transplant them outside. It also gives general information for when you can plan to harvest those plants (so you’re not swamped with your entire harvest being ready all at once).

Read more on how to use Clyde’s Garden Planner (and watch the video).

If you’d like to order your own garden planner, visit Clyde’s Vegetable Planting Chart and use code “HOMESTEADINGFAMILY.COM” to get 10% off your order.

The Size of Your Seed Starting Pots

Knowing when to transplant your starts outdoors also depends on the size of your seed starting pots or trays.

A general rule of thumb is that you’ll start your seeds 4-8 weeks before transplanting them outside. But if you need to extend this time a bit longer (say for tomatoes which have a longer growing season), you might need larger pots to allow the plants to grow bigger.

A man holding up a tray filled with seed starting pots.

Which Seeds Can You Start Indoors

Technically speaking, you can start ANY seeds indoors. But this doesn’t necessarily mean you need to.

Some seeds are easier than others, so it just depends on whether you need that extra control that starting seeds indoors gives you.

Again, if you know your climate, the length of your growing season, your average temperatures and if you have healthy soil, then many plants can be directly sown outdoors with no problems.

For us in North Idaho, we will always start tomatoes, peppers, cucumbers, long-day brassicas and melons indoors because our growing season just isn’t long enough.

However colder-weather crops such as lettuces can be directly sown in early Spring.

What Do You Need To Start Seeds Indoors

You don’t need an elaborate system to start seeds indoors, however, there are a few items that will be helpful:

Seeds
Trays and pots
Markers
Potting soil
Water
Grow lights or a sunny window

Seeds

As we mentioned before, make sure your seeds are high quality and that you’ve checked the seed packets for how long it takes the seeds to germinate, when you should plant outdoors, and the average time to harvest. This will give you an idea of when you should sow seeds.

Trays/Pots

There are many options when it comes to seed starting trays and pots. Some people prefer to grow in peat pots, others in large trays with multiple compartments. I prefer slightly larger individual pots.

These pots work well for seeds that need a bit longer before transplanting.

We prefer them because they’re very sturdy, reusable and because we plant our garden in large, long rows. Not having all our starts in one single tray means multiple people can be planting a row at the same time because each pot is separate.

No matter what your choice, make sure your pots have adequate drainage holes and that those holes don’t get clogged up.

Markers

Having markers is very important for remembering which type and which variety of seeds you’ve planted. Trust me when I say there’s nothing worse than getting all your seeds planted and then not remembering what you put where.

Using markers and putting them in the pots before adding your seeds will eliminate this possibility.

We like plastic markers because they’re reusable and will last for many years.

Soil

When starting seeds indoors you’ll want to have a seed-starting soil that’s moist but not too wet. It should just hold together when squeezed with your hands (see photo above), but not stick to your hands or turn your hands black.

We actually don’t recommend buying potting mix from garden centers because they’re typically sterilized before bagging and devoid of life.

If you have the means to make a seed starting mix we recommend mixing 50% garden soil with 50% good quality sifted compost. (Watch how we sift our compost here.)

If you have clay in your soil, you may have to experiment with these percentages and possibly add some sand to help it out.

If you know you have fungus and/or disease problems you may want to go with a store-bought mix, but most of us won’t need to do that.

If you’re going to spend your money, spend it on a high quality compost over a seed starting mix.

Water

You’ll want to have water on hand because your soil will need to stay nice and damp to allow for germination.

When you’re watering your starts for the first time, you’ll need to water them a lot more than at any other time.

For our seed trays, this means filling it up 1/2-2/3 full then giving the plants 12-24 hours to “drink up” all that water. If there is still water in the tray after 24 hours, dump that water out and begin watering normally each day.

If after 12-24 hours the tray is dry, add water to fill the tray about 1/4-1/2 full again and wait another 12 hours. Then remove any excess water.

Grow Lights or a Sunny Window

Once your seeds are planted, they’ll need light. Using grow lights or a nice sunny window will work great.

We love heat mats, especially if you’re growing your starts in a cooler area, such as a basement or cold room.

We actually prefer growing starts in the basement because it’s easier to control the temperature and light using heat mats and grow lights.

If you’d rather not invest in mats or lights, you can adjust by finding a sunny windowsill, or a warm, well-lit area of the house.

Alternatively, if your weather allows, you can take your starts outside during the day, then bring them inside at night. This temperature variance can sometimes be hard for more finicky plants, but if the temperature swings aren’t too drastic, you should be fine.

Ideally, you want to keep the soil temperature above 60 degrees.

We found using fluorescent lights works well as a light source, especially if you’re only growing for about 4-6 weeks before transplanting. If you go much longer than that your plants could end up lanky and weak without access to a stronger light source.

We keep the lights about an inch above the plants and, as they grow, move the light up.

Seedlings growing in a seed starting tray.

How to Start Your Seeds Indoors

Once you’ve got all your components together, planting the seeds is the easiest part. Here are the basic steps:

Add soil to your pots
Tamp down the soil by lightly banging on the counter (you don’t want any air pockets in your soil or your roots may die when they hit it)
Label and put your markers in your pots
Sprinkle 2-3 seeds per pot
Cover with a small layer of soil (2 times the greater width of the seed)
Water well
Have a source of consistent heat & light

Seed Starting Tips

We don’t like to poke “holes” in our soil where the seeds will go. Oftentimes we find our seeds get too deep this way. The only exception to this rule is for larger seeds like corn or beans.
It’s important to tamp down the soil in each pot before planting so there are no air holes in the soil. If roots of your plant hit an air hole they can die back, or die completely before you know what’s wrong.
Water from the bottom up! This helps you know your plants are neither too dry or too damp.
If you have extra seeds after planting, store them well and they should be good the following year. If planting older seeds, we generally plant a couple extra.

As those seedlings grow in size, they may need to be transplanted into bigger pots before planting them in your garden. When that time comes, here is our easy tutorial on potting up seedlings.