How to Start Seeds Indoors (Spring Gardening)

Learn how to start your seeds indoors to get a jump start on your garden! Plus download my free printable seed starting log book!

Everything you need to know about: Starting Seeds Indoors

If you live in a cooler climate that prevents you from growing fruits and vegetables with a long growing period, you might consider starting seeds indoors!

By starting seeds indoors, you can get a jumpstart on your vegetable garden and grow vegetables that wouldn’t typically thrive in your gardening zone. Read below to learn how to start seeds indoors!

Step 2: Germination

Use sterilized equipment: this is important for success! You may think you can skip this step – but don’t! To sterilize gardening tools soak them in a 10% bleach solution (9 parts water: 1 part bleach) for 30 minutes, then rinse well. Note: if your tools are brand new, don’t worry about bleaching them.

Fill each seed starting container with seed starting mix. It is important to use seed starting mix rather than potting soil.

Seed starting mix contains the proper nutrients necessary for starting seeds, and is free of any bacteria that can potentially hard the young plants as they develop. You can alternatively use seed starting plug (pellets), simply plant the seed directly into the pellet and germinate as usual following the steps below.

Determine how deep to plant each seed into the pellets or containers (this information is on the seed packet). Each seed has different depth needs, and it is important to follow this pretty precisely.

You can mark an unsharpened pencil with measurements to use as a marker when creating holes for the seeds. If planting in rows, make sure to follow the seed packet guide for seed spacing.

Germinate the seeds by covering the trays/containers with plastic, and place them in a warm area, ideally 65-75 digress F. Bottom heat will provide you with the best results, so the top of a refrigerator is often recommended, but you can purchase a special germination tray that provides heat and airflow.

Humidity is key for proper germination, you want a warm moist environment for the seeds to germinate. Do not saturate the seedlings – the soil should be that of a moist kitchen sponge. DO NOT PLACE IN DIRECT SUNLIGHT.

Check daily for germination. The seeds have germinated once you see them peek their heads out of the soil. Once they have germinated, remove the plastic cover, and move to a well lit area.

Step 3: Growing Seedlings After Germination

Once the seeds have germinated, they will need direct sunlight to thrive. Place the trays in a bright, south facing window.

It can be difficult to provide enough sunlight indoors in the early spring, so a grow light is often used. Place the trays under the grow lights to provide continuous, steady light. As the plants grow, be sure to raise the lights. The fluorescent tubes should be 3-4” away from the plants at all times.

Plants should receive 14-16 hours of sunlight per day. Keep temperatures around 65 F. If the temperature goes too much higher than 65 F, plants can become spindly, and fail to thrive.

You can check soil temperature with an instant read thermometer. Plants will thrive with adequate humidity, and the use of a humidifier is helpful.

Keep plants moist, and do not overwater. Allow the plants to dry between waterings, but do not allow the plants to wilt. To water, the use of a mister is beneficial for the delicate young plants.

Fertilize the plants: After the plants have germinated, fertilize in two week increments. Be sure to dilute fertilizers properly as too much fertilizer can do more harm than good.

Use a spoon or spatula to gently cup the seedling out of the growing tray. Place into a small growing container (such as a small terra cotta pot or even a red solo cup).

Fill with seed starting soil and dig a small hole in the new container, place the plant into the soil and pat the soil down. Water gently, and place back under the lights.

If you need to handle the plant, handle it gently by the leaves as the stem can be crushed easily. Drainage is very important as is cleanliness. Make sure to poke holes in the bottom of the container and only use clean tools (hands included!).

Allow the plants to continue to grow until the last frost approaches. Before transplanting to the garden, be sure to harden off the plants for best results. (see below for more details)

When to Transplant Seedlings?

Transplanting seedlings outdoors is like sending your newly graduated children off to college! You’ve worked hard for weeks to raise your plants to be ready for the great outdoors, but before transplanting your young plants, be sure to harden them off first!

Step 6: Transplanting

Once your plants have grown to an easily handleable size, and have been hardened off, it’s finally time to plant them in your garden!! Be sure to only transplant to your garden once the last frost has passed.

How to transplant seedlings: Dig a hole about twice the size of the plant’s root mass (example: if the root system is the size of a softball, dig a hole the size of a volleyball). Gently remove the plant from its container, and place it into the new location, preserving as much of the seed starting soil as possible.

Place the plant in its new home, fertilize with a starter fertilizer, and cover with soil. Gently tamp down the soil, and water.

Transplanting is best on a cloudy day. If a cloudy day isn’t possibly, transplant in the afternoon after the peak of the sun has passed.

Now your plants are ready to thrive in their new home in the garden! Enjoy the fruits of your labor during throughout the summer!