How to Start Seeds Indoors in 8 Simple Steps

Soil to start seeds

Combine one part compost, one part vermiculite and two parts coconut coir for an easy seed-starting potting mix. It is also acceptable to purchase seed-starting potting soil from a garden center.

Whether you make your own potting soil mixture or purchase some, it is usually fully dry. Add water to hydrate it. This will cause the soil to inflate and make it easier to break apart. Once it becomes soft and pliable, break it up with your hands or a small garden shovel, making sure all of the mix is hydrated and fluffy.

• Tip: Make sure the soil is moist before planting seeds to prevent them from being displaced or sinking too deeply into the soil mix.

watering the soil mixture

Transfer the soil mixture

Fill potting trays or two-inch organic pods with the soil mixture. Fill to the top, but don’t compact the soil mix down too tightly. You want the seeds to have room to sprout without a lot of effort or energy spent finding their way.

Tip: Cardboard toilet paper rolls work wonderfully as a potting reservoir because they are organic, allow moisture to pass through, and are small enough to make a seed feel snug.

transferring soil mixture to potting tray

Plant the seeds

Excavate a hole in the center of the potting mix with the handle of your garden shovel or a small seed sowing tool. Be sure to read the specifications for each seed type to determine the depth.

You want your seeds deep enough to be covered and shallow enough to allow the shoot to find its way up and out of the dirt. Some seeds make it easy to determine which side of the seed is up and which is down.  If detectable, place the seed so the roots easily grow into the dirt and the sprout easily finds its way up.

planting seeds

Label your seeds

Use plant tags and a permanent marker and label your seeds. You may think you will remember which is which, but you may easily get them confused. It is crucial to know which sprouts are which to continue with the ideal light, water and temperature environment for a successful harvest.

adding plant tags to potting tray

Mist with water

After planting the seeds, you may lightly mist the soil mixture. Use a gentle spray of water to avoid displacing the seeds. You should also ensure an easy drainage path for the water to drain through the seed trays or pots.

misting seeds with water spray

Place on a heat mat

Seeds need warmth to grow—between 65 and 70 degrees F is ideal. Heating mats ensure the dirt is at an optimal temperature for growth. For this reason, plants should not be placed in the ground outdoors until the ground temperature is at a level that will allow the seeds to grow and flourish.

Once you have planted the seeds, place them on a heating mat until they sprout and start showing their first leaf, called cotyledons. Once you see these emerge, you can place the tray under light for 12 – 16 hours daily.

planted seeds being placed on heating mats

Introduce a grow light

Once the cotyledons have emerged, you may introduce grow lights. Seedlings need 12 to 16 hours of light daily. Place the grow lights about 4 inches away from the sprouts until they are ready to begin hardening for outdoor transplantation. Make sure the grow lights are not touching the leaves.

introducing grow lights to seedlings

Start fertilizing

Once the sprouts develop true leaves, start fertilizing until they are ready to be transplanted. Fertilize sprouts every two weeks with ocean water (rich in nutrients) or a balanced fertilizer to encourage good roots and healthy growth. If using a water-soluble fertilizer, it is very important to use it diluted to one-half the normal strength.

FAQ

When it comes to starting seeds, what is a blackout period?

A blackout period, mostly used when growing microgreens, is a time when seeds or microgreens are kept in complete darkness to encourage specific growth processes. The length of the blackout period (two to seven days) depends on the variety of microgreens and the desired outcome. The blackout period encourages the development of root systems and longer stems, making the microgreens more tender and flavorful.

What does it mean to sacrifice a seed?

Some seeds, like beans, must be scratched (scarified) and soaked for 24 hours before planting. This will allow moisture to enter the seed and activate germination. This is easily done by scratching the outer layer and placing it in a Ziploc bag with water before putting it in the soil mix.

Why do some seeds (especially flowers) require refrigeration before planting?

Many wildflowers or plants that usually spend the winter buried in the ground getting ready for the spring need to experience cold stratification before planting. To replicate this cold period, this may be done by placing the seeds into the refrigerator or placing the seed packet outside for at least a month.

seedlings in potting trays