How to Start Seeds Indoors

What is Seed-Starting?

Seed-starting refers to germinating seeds indoors in a controlled environment before transplanting them outside.

It's a popular technique for many gardeners because it allows you to get a head start on the growing season, especially for plants that take a long time to mature from seed.

For example, tomato seeds are often started indoors and then transplanted outside once the weather is warm.

Here are some of the benefits of seed-starting:

• Earlier harvests: By starting seeds indoors, you can harvest your vegetables and flowers weeks or even months earlier than you could if you planted them directly outdoors.
• Improved germination: Seedlings are more vulnerable to pests and diseases outdoors. Starting them indoors allows them to grow strong and healthy before they are exposed to these challenges.
• Larger selection of plants: Many plants, such as tomatoes and peppers, are difficult to grow from seed outdoors in cooler climates. Seed-starting allows you to grow a wider variety of plants in your garden.

Supplies You'll Need

• Seeds: purchased from a reputable seed company
• Containers: paper pots, recycled toilet paper rolls, or reusable cell trays
• Hydrogen Peroxide: used to sanitize reusable containers (look for 3% Food-grade Hydrogen Peroxide)
• Soil: use a good-quality seed-starting mix or potting soil (not garden soil)
• Earthworm Castings (optional): a soil amendment that helps plants grow bigger and stronger (yes, worm castings are worm poop!)
• Vermiculite (optional): vermiculite is a soil additive made from an expanded mineral used for soil aeration
• Garden Marker: look for an indelible marker that is made for gardening
• Plant Labels: popsicle sticks, wooden labels, plastic labels, etc.
• Light: grow lights work best, but a sunny window can work
• Heat Mat (optional): a seedling heat mat can speed up germination by keeping the seed-starting mix warm
• Plastic Dome: a humidity dome or any plastic cover that can trap heat and moisture around your seedlings to help them germinate
• Water: a plant mister works well for freshly sown seeds, but a watering bottle can also be used once seeds have sprouted
• Fish Emulsion or a Soil Enhancer (optional): an organic product that provides essential nutrients to your plants (I use MARPHYL Soil Enhancer)
• Fan: An oscillating fan provides air circulation and may help strengthen seedlings

Helpful Tool: The Staedtler garden marker works particularly well on popsicle sticks!

Reading the Seed Packets

It’s important to know how and when to plant your seeds, and the best way to figure that out is to read the seed packet.

Things to take note of on the seed packet are:

• when to start the seeds (i.e. 6 weeks before your last frost)
• where to start the seeds (indoors or outside)
• recommended planting depth for the seeds (large seeds can usually be planted deeper than small seeds)
• the germination rate (if listed)

If the packet shows a low germination rate, you may want to start more seeds than you think you need.

If you don’t know your last frost date, I have an article on how to find your frost dates and planting zones that you might find helpful.

Tips for Planting Small Seeds

Small seeds can be difficult to plant due to their size.

Try to just dust a small amount of seed-starting mix on top of them, instead of pushing the seeds down into the mixture.

Burying tiny seeds can prevent them from germinating.

Also, smaller seeds should be started in smaller containers and need to be watered gently to avoid washing them away.

How to Start Seeds (step-by-step)

This is the method that I use to start my seeds indoors.

It might look like a lot of steps, but once you get the hang of it, you won't even need to look at this list again.

Plant the Seeds

1. Use the tip of a pencil or wooden skewer to poke holes into the soil. Alternatively, you can buy a dibbler, but you don't really need one.
2. Sow seeds according to the package directions. You will usually want to sow 2-3 seeds per pot in case one of the seeds doesn't sprout.
3. Cover the seeds lightly with more seed-starting mix and then a layer of vermiculite.
4. Mist with water until damp (not soaking wet).
5. Label each container before you move to the next one.

Why Add Vermiculite?

Sprinkling a light layer of vermiculite over your seeds after sowing (but before watering) can help prevent a fungal disease called damping off, which rots the stems of seedlings.

Provide a Lot of Light

Growing seedlings need a lot of sun – 12 to 16 hours worth of it!

Place your containers in the sunniest windowsill, moving it as needed if it can't get enough light in one spot.

If you're using a grow light, it needs to be relatively close to the seedlings to prevent them from becoming “leggy” (overly tall with thin stalks).

The distance between your lights and your plants will depend on what kind of grow light you have. You can learn more about using grow lights here.

Water Your Seedlings

It's important that you don't let your seeds or seedlings dry out. Check them daily to see if they need to be watered.

Bottom watering is the best option for watering seedlings, but this doesn't always work well with recycled seed-starting containers.

In that case, I would use a watering bottle instead.

Watering Tip

Overwatering creates soggy soil, which is ideal for fungal growth. You may also end up with fungus gnats, as they also thrive in moist environments.

Next Steps

Once your seedlings look like they're getting too big for their containers, pot them up into a larger container.

If the weather outside is warm enough, you can being the hardening off process so they can eventually be planted outside.