March 19, 2021 4 min read

How to Start Seeds Indoors

    With the sunshine making more appearances as of late, we find ourselves anticipating the warm summer days we spend outside, tending to our gardens, wondering, “What will we do with all of these tomatoes!” Spring is at our doorstep, but peak gardening days are still a little ways away. In the meantime, bring your gardening inside! Have you ever wondered how to start seeds indoors? Here’s a quick rundown on what you need to know.

Things You’ll Need to Grow Seeds Indoors

    The essentials you need:
Lightweight soil mixture that won’t retain too much water like our EB Stone Seed Starting Mix.
Fiber or plastic cell pots to hold your soil and seed.
A drainage tray to catch water from your cell pots.
Also maximize success by using a biodome or mini-greenhouse, this will retain the humidity and help keep the soil moist.
    If you are not in Portland, you may not necessarily need a growing light. However if you are in Rose City, we are known for our grey winter skies, and seedlings need a lot of light and comfortable temperatures (65°-75°) to grow. A lot of the produce we grow in our gardens are originally from places closer to the equator that receive much more sunlight throughout the year. For our demonstration we used the Sun Blaster Growlight Garden, which we carry here at Cornell Farms.

Common Mistakes When Growing Seeds Indoors

    1. Not enough light is number one. As we learned in grade school, plants require sunlight for photosynthesis, which is how they make their food. Without enough light, the plants will stretch, stems will not be strong, therefore create a weak plant. This is especially important for plants like tomatoes, cucumbers, peppers, etc.
    2. Watering habits are important for seedlings. Overwatering is the most common cause of seedling failure. The soil should always be damp, but not soaking. The roots of plants need air, more specifically oxygen. Overwatering your plant in essence drowns the plant as it cannot get enough oxygen from its roots. Also when watering seedlings, its best to water them from the bottom up, i.e. letting plastic cell pots soak up water but not sit in water longer than 15-20 minutes. Pouring water on top could disrupt the seed and the soil, causing the seedling to be exposed directly to light and air.
    3. The depth at which you plant your seeds is also important. Too deep and the seedling may never reach the surface after it germinates. Too shallow and a shift in the top soil could expose the seedling too early. Consult the seed packet for instruction on each particular variety, as it can vary widely even within the same species.
    4. When starting seeds indoors, it’s important to “harden off” the plants. They cannot go straight from growing indoors to being planted outside. This process of acclimating a plant is simple but crucial. When the time is appropriate (read seed packets), plants should be placed outside for increasing periods of time. This should take place over the course of about two weeks. The first day they should be outside for about an hour, and the last day they should be outside for the majority of the day. This allows the plant to adjust to, wind, varying weather, and direct sunlight.
    5. Lastly, when sowing your seeds, pay attention to how much space they require from other seeds. Plants that are too close to each other will stunt each others growth as they do not have enough room to expand and their roots will get tangled up.

Growing Tomatoes from Seed

    Once you have your supplies, start by placing some soil in a separate container. We used E.B. Stone Seed Starting Mix for our soil, but a mix of peat moss and perlite will do. Wet your soil mixture before hand to prevent any dry spots in the soil upon the initial seeding as well as not require heavy initial watering.
    Fill your cells or pots with the soil mixture and pack it down just enough so there aren’t any air pockets. Tomatoes are typically sown a quarter, to a half inch in depth but be sure to check the seed packet for specifics. Once the seeds covered in the soil, lightly water them, remembering that the soil is already hydrated. Use something that dispenses the water gently as to not disturb the newly planted seed. We used a mini watering can with a showering spout. Then put your seeds under your grow light or next to a southern-facing window with excellent sun exposure. From here, check your seeds daily, watering as necessary to keep the soil moist.
    Once your seedlings reach around three inches tall, or develop true leaves above the cotyledons (the first two leaves that shoot out once germinated) , it is time to move them into their own 4” pots. When re-potting, bury the seedlings up to their leaves (not covering the leaves). Continue to leave them in the same watering and light conditions as before. When your plants get around six to seven inches tall, start acclimating them outside, i.e. hardening off. Do not simply set them outside and forget about them. Be aware of the temperature, the wind, and weather. You don’t want the seedlings to be soaked from rain, scorched by the sun or beaten by the wind. The intention is to adjust the plant to these conditions, so gradual doses of these conditions are what we are looking for. After about two weeks of hardening off and nighttime temperatures are above 50°F, it’s time to plant! Put your tomato plants in your garden beds or large pots, put a cage around them to support the branches, and watch them grow! Tomatoes love fertilizer so we recommend using E.B. Stone Sure Start when you transplant and E.B. Stone Tomato & Vegetable Food every one to two weeks afterwards.
    Hopefully everything went according to plan and your seed starts grew exactly how you wanted! However if you make a mistake, give it another shot. Trial and error is inevitable in gardening, and as Thomas Edison said, “Our greatest weakness lies in giving up. The most certain way to succeed is always to try just one more time.” If you have any questions about how to start seeds indoors, feel free to email us at Outreach@cornellfarms.com