How to Start Seeds Indoors

Watching a seedling sprout forth from soil is one of the most satisfying parts of homesteading. Seeing that green pop up at the surface and reach toward the light is so... gratifying. Starting seeds indoors just gives me that boost of energy to know that spring is just on the horizon and we will be growing an abundant garden soon.

Starting seeds indoors is pretty simple once you get the hang of the basics. It allows folks, especially those of us with shorter growing seasons, to grow vegetables, flowers, and herbs that otherwise we wouldn't be able to grow because the season isn't long enough.

It opens up the opportunity to grow things like peppers, tomatoes, even onions, from seed. Even though it may be months before outdoor temperatures are adequate to support these plants, you can start them inside and get a jumpstart on the growing season.

Benefits of Starting Seeds Indoors

Lengthens the growing season

As I mentioned, it gives you a head start on the growing season, enabling you to grow varieties that need more growing time than you have season.

More Variety

There are more varieties available if you start your own from seed. Garden centers usually have a select few varieties available of each plant. When you start from seed, you can purchase seeds of many different varieties.

Saves Money

Starting from seed is much less expensive than buying starts from the local store. You can buy an entire packet of seeds cheaper than a single plant or 6 pack from most nurseries.

Healthier Plants Raised How You Want Them

Buying seedlings from the store can have its benefits, sure. But, oftentimes, especially from big box stores, the plants aren't particularly healthy and not as likely to thrive as a homegrown seedling. You also know exactly how that seedling was grown so you can grow it organically or however you see fit instead of not having the knowledge of what was sprayed on it before it made it to your garden.

When to Start Seeds Indoors

Different seeds require different lengths of growing time before they're transplanted outdoors. You don't want to start seeds too early, or too late, so knowing when to start seeds is important.

Each plant needs a set amount of time to reach maturity before it goes outside. Growing onions, for instance, takes quite a while before they're put outside. Tomatoes, need a couple of months of growth as well. Whereas lettuce, cabbage, and broccoli don't need as much growing time before they're put outside.

When you start a particular seed is going to depend on two things: how long it takes for it to grow before it can go outdoors and your particular growing zone. You can check the back of the seed packet to figure out how many weeks a seed needs to be sown indoors before it is transplanted (or if it's recommended to sow directly outside). You can check this website to find your last predicted frost date.

Seed Starting Supplies

• Seeds
• Soil or seed starting mix
• 10X20 seed trays, starter cells (or soil blocker), humidity dome
• Grow lights
• Tape, marker, and a sheet of paper for your garden journal
• Watering can

Seeds

Of course, to start seeds you need to actually have some. You can find a variety of vegetable seeds locally, or check out one of my favorite places to buy organic seeds, or of course if you've saved seeds you can use your own seeds.

Soil or seed starting mix

I used to make my own seed starting mix, plant in cells and pot up in a few weeks time. I found all of this process time-consuming and completely unnecessary.

While a lot of folks will tell you you absolutely have to have a sterile growing medium and that the seed has plenty of energy to sprout (it does). You don't. I know people that start in compost, people that start in garden soil, and people that use regular potting soil. They all work and there are benefits and drawbacks to each growing medium.

We no longer use cells, instead we make soil blocks using a soil blocker. No more fancy seed starting mix, either. I just use regular old potting soil. This makes it easier on us. We don't have to fertilize or transplant our seedlings near as often by using potting soil up front. It's also cheaper for us than buying bags of starter or buying the stuff to make our own only to transplant into soil later.

Trays, Cells, and Humidity Dome

One thing you can never have enough of as a gardener, despite the fact that I loathe plastic, is solid 10X20 trays. I buy heavy duty trays from greenhouse megastore. They're fairly inexpensive and much more sturdy than most of the stuff you find at the big box stores.

The humidity domes are sold separately, but necessary unless you want to use plastic wrap. These last longer, are a more heavy duty plastic and pretty sturdy. I love that they should last for quite a while.

They also have all manner of cells, daisy trays, and more. As I mentioned, we don't use cells anymore, we use soil blocks. But, you can find something suitable for you or make your own DIY seed starting container from stuff you have lying around. Remember, these seedlings are likely going to require larger containers to transplant into before they're put in the garden.

Regardless, you can buy the seed starter kits at the big box stores and get what you need all in one. Most are sold as a three-part set. So, you get cell packs, the tray, and a humidity dome.

Grow Lights

Light is essential for plant growth. All plants require light in order to photosynthesize, some more than others. In fact, there are certain seeds, mostly herbs and some flowers, that require light just to germinate.

You can use T8 or T12 fluorescent lights in a shop light fixture and accomplish what you want to accomplish. LED lights will accomplish that same task using less energy as long as they are all-spectrum.
Personally, we use T5 florescent bulbs as they are more efficient and what we've had the best luck with. But, you don't have to have super fancy grow light specific fixtures to grow seedlings. Just work with what you have, as long as it isn't just a sunny window as this will likely make your seedlings leggy trying to stretch toward the light.

Tape, marker, pen, and sheet of paper

I recommend labeling your trays with cell numbers instead of trying to put individual labels inside the trays. The labels are often too tall to put in place with a humidity dome on, which needs to be on until they start to sprout, and using other methods usually results in labels that get ruined by water before the seedlings are ready for transplant.

I use painters tape and label one side and the top of each tray. Then, label each cell row and column. Once you start planting your seeds, take out a sheet of paper and write the variety and which column and rows the seeds are in. Such as Cherokee purple row 1 columns 1-4. Then, place this paper in your garden journal so you can recall what's where in your seedling trays.

Watering Can

Some people spray their seedlings, I recommend bottom watering. If you have cells, you'll have to pull up a corner in order to water from the bottom, the cells have drainage holes in them in order to suck the water up into the soil. If you're using soil blocks, leave space between each block so you can water via the channels between each block.

Don't use a watering can from the top as this will flood out your trays and could create problems with rotting and disease in the seeds and plants. Another reason I prefer potting soil as it more readily absorbs the water evenly than starting mix. Also, it's worth noting that if your watering can has a diffuser on it, it needs removed to water seedling trays.

Use warmish water when you water so you don't shock your seedlings with a super cold rain, even if you are watering from the bottom!

Optional: Heat Mat

Personally, I don't use heat mats, but they do have their place. Heat mats are available that are the same size as a 10X20 tray and help warm up the soil temperature to make it more hospitable for warm-weather plants such as tomatoes and peppers to sprout up.

Our home is warm, I use a humidity dome, and the seedlings are setting near a south-facing window so the soil gets and stays pretty warm. A mat can help, though.

Optional: A shelf, indoor greenhouse, or table

There are tons of fancy seed starting kits online that have the shelves, the grow lights, and sometimes even greenhouse covers on them. They're convenient, and you pay for that convenience, royally.

You do have to have a place to put all of those trays, though. We usually have a minimum of 16 seedling trays started and sitting around before our last frost date. Originally, I had a folding table we put them on, then I ran out of room and started putting them on the kitchen counters, then I had no room to cook food.

So, we bought a shelf. It was far less expensive than those kits and fits 4 10X20 trays on each shelf as well as perfectly fits our chosen grow lights which we can hang from the above shelf since they're made of wire. It goes out in the garage and stores our supplies in the off-season.

How to start seeds indoors

Step 1

Fill a 10X20 tray with soil mix and use your watering can to moisten it well. If you're making soil blocks, add a little more water than if you're using cells.

Step 2

Put your cell tray inside another solid 10X20 tray, alternatively you can make soil blocks and place those inside the 10X20 tray.
If you're using cells, fill each one to the top with the moist soil mixture. Place tape on one side and the top of the tray and using a marker label each row and column with a number.

Step 3

Sow the seeds! For things like lettuce, snap dragons, and many herbs you'll simply sprinkle a few seeds on the surface. For larger seeds, a good rule of thumb is to plant the seed twice as deep as it is wide.

Cover each cell, or soil block indent, with a bit of soil unless it's a seed that requires light to germinate (check the seed packet to be sure). Be sure you're taking note of what cells each seed is in and writing it down on the paper for your garden journal.

Step 4

Cover the planted tray with a clear, plastic humidity dome. Place it on a heat mat if you're using, and under the grow lights. Remove the dome once you start to see seedlings sprout.

Caring for seedlings

They're sprouted and you have cells full of healthy seedlings. Now what? It's pretty simple, they only need light, water, and a bit of fertilization (this is especially true if you used seed starter).

Light

As mentioned, while many people have lots of luck with growing in a nice, sunny window, you really need a grow light. There are many different options available for just about any space from single bulbs to huge fixtures.

Seedlings are going to require 12-16 hours of light a day. Which is part of the reason using a window isn't ideal since no one is getting that much direct sunlight daily in the winter. Hooking your lights up to a timer can really help because you don't have to worry about turning them off and on daily.

For us, personally, we just turn them on in the morning as part of our morning routine and shut them off in the evening before we head to bed, they get that 12-16 hours every day, we just have to flip on two surge strips to make it happen.

Water

With the humidity dome on, you're not going to have to water very frequently as it will keep a lot of that water trapped inside. However, check on them in the mornings to make sure the surface level of the soil is nice and moist, but not drenched.

Once the seedlings begin sprouting, you can pull the dome off as you don't want those seedlings to get dampening off disease. Now, you'll have to keep it watered more frequently as the moisture will evaporate more quickly, especially with the lights on.

To water, check the surface of the soil to see if it's dried out. If it is, lift up the corner of your cells and fill up the tray about ¼ of the way up and place the corner back down. This will provide adequate water and won't cause issues with the seedlings.

Fertilizing

This isn't as essential if you're using soil or compost, but it still doesn't hurt. After your seedlings have two sets of true leaves and then every two to three weeks after, you can mix up some fish emulsion and water with that instead of just plain water. This smells funky, but it works wonders.

I always, always fertilize onions since they can be pretty heavy feeders and don't have a lot of surface area to photosynthesize. There are other fertilizers available, but we use and have the best luck with the stinky fish emulsion.

A note on thinning

Since we started using soil blocks, we typically don't start more than one seed in each block. But, in the off-chance we do, they need thinned (even in cells). You have two options for this. You can thin the weakest, smallest plant and put it in your compost pile or you can very gently remove it and transplant it into a new, shiny container all its own.

Transplanting

Seedlings will likely need transplanted into larger pots at least once and then out into the garden.

The seedlings will need properly hardened off before being transplanted and I have an entire article on how to pot up and transplant seedlings here.

Happy gardening!

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