10 Easy Steps for Successfully Starting Seeds Indoors

Curious about starting seeds indoors? Some plants such as tomatoes, peppers, and Shasta daisies require a longer growing season than we have here in the Chicagoland area (we’re hardiness Zone 5B). To ensure healthy growth, many gardeners prefer to start seeds for these plants indoors in the spring. Starting your own seeds is not only less expensive than purchasing transplants, it is also very rewarding to watch your seeds grow into healthy full-grown productive plants. Plus, it’s fun! Here are our 10 easy steps for successfully starting seeds indoors:

Step 1

Check out seeds from the Bensenville Community Public Library’s seed library!

Or purchase seeds from a reputable company. For more information on the Library’s Seed Library, visit benlib.org/seed-library.

Check the seed packet for your hardiness zone to ensure that the seedlings with thrive in your area when transplanted outdoors. Most seeds are started indoors 6-8 weeks before last frost date, which for our area is, on average, May 15th.

Step 2

Start with clean containers.

You can use recycled pots, such as empty, clean yogurt containers or disposable plastic cups. Although not necessary, commercial seed starting trays are a good choice and can be reused year after year. Mark each container with the name of what’s growing inside or it will be difficult to tell what is growing when the seeds begin to sprout. Place several small holes in the bottom of the container for drainage and ventilation.

Step 3

Fill each container with a quality seed staring mix.

A seed starting mix does not contain any actual soil, but it does provide an ideal condition for sprouting seeds. It provides a good balance of drainage versus water-holding capacity. Seed starting mixes also minimize problems with disease on susceptible seedlings.

If you can, avoid using garden soil or potting soil to start seeds. These don’t generally drain well and may contain plant disease spores. If you must use one of these, potting soil is your better bet. If possible, run some boiling water through your potting soil prior to use to kill any contaminants.

Step 4

Refer to each seed packet for planting instructions.

The seed packet contains valuable information — such as the proper planting depth, when to plant, or days to germinate. All the information you need for each plant should be on the packet. Need more info or lost your seed packet? A quick Google search (i.e. “marigold seed starting information”) will also get you the information you need.

Step 5

Cover those seeds!

Cover the top of the tray with the clear dome that came with your seed starting tray, or cover your pots with clear plastic wrap. This helps keep the potting soil moist. New seeds need to be kept warm; place seed trays or pots in a warm location, but out of direct sunlight.

For faster germination use a heating mat made specially for starting seeds under the tray or pots. Don’t have a heating mat? No problem, you can also sit the containers on top of a warm spot such as the top of the refrigerator. Check regularly for signs of growth. Once germination begins and seedlings start to sprout, remove the plastic wrap.

Step 6

Move your seedlings to a sunny location.

Seedlings need water, air, and light to thrive. Place your seedlings in a bright, sunny location — or some gardeners choose to place their seedlings under supplemental grow lights. Make sure to water consistently, but do not overwater! Seedling roots need both air and water. Try to keep the mix moist but not saturated with water — think of it as a damp sponge that contains both water and air. Warmer temperatures are no longer necessary to continue growth, moderate temperatures with a good light source will help to grow thicker, sturdier seedlings.

Step 7

Thin your seedlings.

You will want to keep one seedling per pot, so choose the healthiest seedling and snip the rest of the seedlings off at the soil line. Thinning seedlings reduces competition for water and nutrients and allows for better air circulation between plants.

Step 8

Fertilize weekly!

Once your seedlings have one or two sets of true leaves (the true leaves will look more like what the plant’s leaves look like when mature), begin fertilizing with a half-strength, preferably organic, fertilizer once a week.

Step 9

Transplant as needed.

If you used a seed starting tray or smaller starter pots, it may be time to transplant your seedlings to larger pots to continue their growth. Seedlings are delicate, so move each one carefully to its larger individual pot and continue to water evenly and fertilize weekly. Place newly transplanted seedlings out of direct sun for a few days to allow the seedlings to acclimate to their new environment.

Step 10

Harden off seedlings before placing outside.

Hardening off is the process by which you slowly, over the course of 1-2 weeks, acclimate your seedlings to the final environment in which they will live. Place plants outside each day during daylight hours in a shaded, protected place. Gradually increase this time outdoors for 1-2 weeks prior to transplanting outside.

Regardless of the type of seeds you're planting, keep these simple steps for how to grow seeds indoors and you will be rewarded with a plentiful garden each year. Happy planting!