Indoor Seed Starting: Tips & Tricks | The Growing Place (2024)

Have you been pouring over seed catalogs and itching to get something growing? Starting seeds indoors is a great way to get a head start on your vegetable garden. We have all the tips & tricks to get your seedlings off to a successful start!

WHAT YOU NEED TO KNOW BEFORE YOU GROW

Timing
Timing is everything when it comes to seed starting. So often gardeners start their seeds too early and end up having to make space for very large seedlings because temperatures are not warm enough to plant those tender vegetables out in the garden.

Frost Dates
Knowing the last and first frost date for your location is important information for any vegetable gardener, but it is particularly useful when growing seeds indoors. Seed packets will often advise the number of weeks before your average last frost date to start them indoors. If you don’t know your average last and first frost dates, you can search for it here.

Best for Indoors
Not all vegetables need to be started indoors. In fact, some vegetables such as corn, beets and carrots, are best sown directly in the garden as they do not transplant well due to their shallow or delicate root system. Plants that have a short maturation are often recommended for direct sowing as well.

Crops such as tomatoes, peppers and eggplant need more warm months than our northern Illinois climate can provide to produce fruit. These seeds are great for starting indoors as they will benefit from a head start to the growing season.

Cole crops such as cauliflower, broccoli, and cabbage as well as leafy greens can also benefit from a head start. These crops are adversely affected by warm weather so giving them a head start indoors allows them to mature to harvest before the summer heat hits.

The good news is, most seed packets will tell you if a particular seed variety is recommended for indoor seed starting or outdoor planting.

GETTING STARTED

You can grow seedlings in almost any container. Egg cartons, yogurt cups, toilet paper rolls or clam shell containers can be repurposed for seed starting as long as you add drainage holes to non-porous containers. You’ll want to use a soilless medium in your containers, such as TGP Potting Mix, as it provides the best conditions for your seeds to germinate.

Seed starting kits often include germination trays, peat pellets (a soilless medium) and humidity domes to help create ideal conditions for seed starting. Some kits even offer a self-watering mat and reservoir so you will never need to worry about overwatering your seedings.

Seedlings will need a light source 1-2 inches above their leaves for 14-16 hours every day. Placing seedlings next to a window can result in leggy, weak stems. Investing in a grow light for your seedlings will help them start out strong.

FERTILIZING & POTTING UP

The first set of leaves that emerge are called cotyledons. The next set of leaves to emerge are the true leaves emerge. This is alsow when you can begin to fertilize your seedlings at 1/4 of the recommended strength.

Once your seedlings have developed 3-4 sets of true leaves, thinning back weaker seedlings sown close together will allow more room for the best ones to grow. Rather than pulling these seedlings out of the soil and risk damaging the root system of your best plants, use a small pair of pruning scissors to snip back at the base of the plant.

Once your plants are several inches high you may want to consider potting up to a larger container. This will allow for better root development and allow more space and airflow between your plants.

HARDENING OFF

Your indoor seedlings will need to acclimate to the outdoors before being directly planted in the garden. Wind, fluctuating temperatures and direct sunlight can damage your seedlings that have not been hardened off. At least one week before transplanting to the garden, gradually increase the amount of time seedlings are left outdoors each day.

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