Starting Seeds Indoors

Backyard Gardening Fb 37

Starting Seeds Indoors

Starting seeds indoors is a great way to get seedlings for transplanting in your backyard garden.

Indoor seed starting is easy, and by growing your seeds indoors, you can have lots of quality seedlings ready to plant outside just as soon as Jack Frost leaves town.

And you’ll have the advantage of not having to depend upon what’s available from nurseries.

You’ll be able to produce any variety of plant you desire, regardless of whether a nursery sells plants of that variety.

Nothing wrong with just buying plants from a nursery, ready to transplant, if that’s what you prefer. You can also look into these best Kentucky blue grass seeds to grow healthy grass after visible decline.

But you might find that growing your own seedlings offers a fair amount of fun, in addition to the other advantages.

Besides, there’s just something particularly satisfying about taking a plant all the way from seed to harvest.

Read on to learn how to start seeds indoors.

Decide When to Plant

Choosing the right time for starting seeds indoors is important. If they’re started too early, the plants will be getting too large before you can safely transplant them to your garden. But if you start them later than necessary, you’ll be trimming days off of your growing season.

And that means, of course, that you’ll also be trimming your total potential harvest for the season.

So to determine when to start your seeds, you’ll need 2 pieces of information: You’ll need to know about how long to grow your seedlings before transplanting them, and you’ll need to know the average last frost date for your area.

For each crop that I write about here on, I’ll provide you with the length of time to grow the seedlings before transplanting them. Also, the seed packet for any crop you’re considering growing will likely give you that information.

Once you know your last frost date, counting back from that date the number of weeks that you want to grow your seedlings will give you the approximate date to start your seeds. In my area the average last frost is around March 15 (yep, I’m down south). So if I were calculating when to start tomato seed, for example, I’d count back 6 weeks from March 15 (tomato transplants should be grown 5-7 weeks before transplanting). That would give me a target planting date of February 1 for starting seeds indoors.

Be careful, though, when that magical last frost date finally arrives.

Before you plop your tender transplants in the ground, remember that the last frost date is only an average. So in many years, the last frost in your area has actually occurred after the last frost date.

More about that when we discuss planting your seedlings.

What You’ll Need For Growing Seeds Indoors


Yes, I know – excruciatingly obvious!

But to be certain that you’ll have your seeds when you need them might take a bit of planning. You’ll want to decide what varieties you’re going to grow, of course. And then you’ll need to decide where you’ll get them.

If you can just mosey down to the corner seed store and buy the varieties you want, no problem. But if you’re going to order your seeds from garden seed catalogs, just be careful not to let time get away from you.

You don’t want to be reduced to nervously waiting for that package from the seed company when planting time has arrived!

By the way, if you’re planning to use seeds left over from a previous season, you might want to check their viability a few weeks before planting time. Those left over seeds will probably be fine – especially if you’ve stored them properly (refrigerated in a sealed container).

But better to check and be sure, and not risk getting behind in the growing season because your seeds didn’t germinate well.

Here’s a simple way to check the viability of most kinds of seeds: Simply fold 10 or 15 seeds within a damp paper towel. Put the folded paper towel in a plastic sandwich bag, and put it someplace where it will stay at room temperature. Check them in 4-5 days.

If most of the seeds have germinated (sprouted a root), then you’re in good shape. Otherwise, you’d best discard that lot, and order some fresh seeds.

Seed Starting Mix…

It’s best to use a sterile seed starting mix for starting seeds indoors.

Seed Starting Tray or Individual Containers…

Obviously you’ll need a container of some sort for starting the seed.

Whatever you decide to start your seed in, be sure that it is sterile. If you’re using flats or containers that are new, then there’s nothing to worry about. But if you’re reusing equipment, there’s a chance that there may be some lingering pathogens that will keep your seedlings from getting off to a good start.

To assure that doesn’t happen, you can just rinse the equipment with a mild bleach solution (9 parts water-1 part bleach).

A Source of Heat…

Each species of plant germinates best at a particular temperature, but most seeds will germinate well at temperatures in the 70’s F.

So for most plants, germination will be acceptable at room temperature.

But to get the very best germination and growth, use a seedling heat mat set to the optimum temperature for the plant you’re seeding. Remember that it’s the soil or seedling mix temperature — not the air temperature — that’s important. A heat mat will provide heat from the bottom, and ensure that the soil mix remains at the desired temperature.

How do you know what temperature is optimum?

The seed packet will probably tell you. And I’ll tell you too, for each crop discussed on this website.

How about light?

For most seeds, light isn’t necessary for germination. There are exceptions, so check the seed packet to be sure. For all plants, of course, light is necessary once the seedlings have emerged, and is obviously a consideration for starting seeds indoors. More about that on the growing seedlings page.

What About Fertilizer?

You don’t need fertilizer just yet.

Once your seeds have germinated, you will need to provide a source of fertilizer as you nurture your seedlings. But since seeds have their own supply of food, it’s not necessary to supply any fertilizer during the planting phase.

Planting Time!

OK, you’ve gathered together everything you need, and the last average frost date is just the right distance away. Today’s the day. It’s time to plant!

And really, this is the easiest step in the entire process.

You’ve already done most of the hard work: Deciding which crops and varieties to grow; determining what to use for a planting mix; choosing the seed flats or containers you’ll use; getting your indoor planting area all set up; figuring the proper date for planting — Whew!

Now it’s time for the fun of actually growing something!

Planting the seed is actually very simple and straightforward. You’ll just want to be sure to get these 3 things right:

Planting Depth…

You don’t need to whip out a ruler to be sure that you’re planting each seed to it’s recommended depth. But you do want to be reasonably precise.

A tiny seed that is supposed to be planted 1/4″ deep will struggle mightily to reach the surface if it’s planted an 1 1/4″ deep. It might make it to the surface and it might not, but even if it does, it’ll be off to a poor, stressful start.

On the other hand, a seed that is planted too shallow may not root in properly, and end up partially sprawled across the surface instead of standing upright.

If you’re not sure of the recommended planting depth, a general rule of thumb is to plant the seed at a depth of about 2 to 3 times the thickness of the seed.

Remember, though, that some seeds (mostly certain flower species) need light to germinate, and so will be sown directly on the surface, and not covered at all.

When covering the seed, be sure to lightly tamp down the soil over it. You want to make certain that there are no air pockets around the seed.


Seedlings are like Goldilocks: They like things just right. Not too wet, and not too dry.

How do you know what ‘just right’ is?

One analogy that’s often used is that of a wrung-out sponge. The dampness of a sponge that was waterlogged and then wrung-out is just about right.

If you could grab a handful of the growing mix and easily squeeze dripping water out of it, it’s too wet. But if you squeeze it into a ball and it doesn’t pretty much hold together in a clump when you release it, it’s too dry.

Uniformly damp is just right.

Be sure to thoroughly wet your growing mix before planting your seeds. In fact, the best way to get your mix ready is to pour some in a bucket, make sure all clumps are broken up, and then stir in some water. Stir until the mix is thoroughly and evenly moistened, and then transfer the mix to your containers.

Once you’ve planted your seeds, covering the tray or container with plastic wrap is a great way to hold the moisture level constant. Check under the plastic wrap every day to see if the mix is getting too dry. And be sure to remove the plastic as soon as seedlings begin to emerge.

When only the surface of the growing mix needs to be moistened, just remove the plastic covering, spray water lightly across the surface using a spray bottle, and then replace the plastic.

If all of the mix needs to be moistened, you can set the tray or container in a shallow basin of warm water (just a couple of inches deep), and allow the growing mix to wick up water.

A Few Additional Seed Starting Tips 

Here are a few additional tips that may help to make starting seeds indoors both easier and more successful:

  • Handling the Seeds
    Some seeds are really tiny, and quite difficult to handle. When planting small seeds, fold an index card in half lengthwise, and sprinkle in some of your seed. You can then use a toothpick to easily slide individual seeds out of the folded card one at a time. A moistened toothpick is also a great way to pick up a small seed. Most seed suppliers offer pelleted seed. Though pelleted seed costs more, in my opinion it’s well worth the extra cost. The pelleting process simply coats the seed with a clay shell, transforming a tiny, hard-to-handle seed into a BB sized, easy-to-handle pellet.
  • Sprinkle on Some Sphagnum Moss
    One of the great enemies of young seedlings is a fungal disease commonly called damping off disease. Sphagnum Moss has natural fungicidal properties that can help to protect your seedlings as they emerge. Simply sprinkle a very thin layer of milled Sphagnum on the surface after you’ve planted the seed and tamped down the soil mix. (If you’re planting a species that needs light to germinate, sprinkle the Sphagnum first, and drop the seed on top.)
  • Use Labels
    If you’re starting seeds indoors for more than one type of plant, or more than one variety of a plant, don’t forget to label your trays or containers. You don’t want to be guessing what’s what come transplanting time!
  • Consider Keeping a Log
    Keeping a log or journal of what you plant, when, how it does, etc. can be a great way of accumulating knowledge and avoiding the duplication of mistakes. Over the years your journal will become packed with valuable info for gardening specifically in YOUR garden, which is at least a little bit different from any other garden on earth — even gardens as close as your next door neighbor’s.

The Season is Underway!

Planting time signifies the beginning of a new season. And starting seeds indoors is a great way to get a jump on the season.

With your seeds properly planted, you’re off to a great start. The hope and anticipation of a successful growing season burns bright.

Let’s keep that great start going by properly caring for those tiny seedlings.

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