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Woman planting seeds indoors from seed packet and second image of seedlings coming up from cups of dirt inside

How to Successfully Start Seeds Indoors

If you’re ready to take your gardening to the next level, start your own seedlings indoors! It’s incredibly rewarding to nurture plants throughout their entire lifetime, starting when they’re tiny seeds. Plus, you can rest assured the plants you’re growing are totally organic, not treated with any chemicals.

Here in the Bay Area, we don’t get weeks and weeks of freezing cold temperatures like other parts of the country, but starting seeds indoors can still give you a head start on your garden.

Supplies Needed for Starting Seeds Indoors

How you treat your plants right from the start will show up as they mature, so it’s important to make sure you have all the materials needed to begin the process properly.

  • Seed starter soil is a particular type of soil that’s ideal for plants to start growing. The soil is sterile, which will ensure moss or mold doesn’t develop in the moist environment needed for starting seeds. We carry E.B. Stones Organics Seed starter mix, which is blended for starting all types of seeds.
  • Seedling trays that have a plastic cover over the cells are the best containers to start seeds. The clear cover helps to maintain the humidity your seeds need to grow while still allowing light to come in. If you reuse seedling trays each year, make sure to wash them well between uses.
  • High-quality seeds set the foundation for success in your garden. The 2021 selection of Botanical Interests Seeds is out now, so you can start planning for and dreaming of your tasty garden!
  • Grow lights help ensure your seedlings get adequate light so that they don’t get too leggy, which results in tall, spindly plants.
  • Seedling heat mats sit underneath the seedling trays and help to maintain the specific soil temperature some seeds need to germinate. Consistent soil temperature will encourage consistent germination.

When and How to Start Seedlings Inside

The seed package will say when to start each type of seed. Generally, it’s six to eight weeks before the last spring frost date.

Once you have the supplies, you’re ready to get started!

  1. Place your seedling tray near the brightest window in your house. Prepare the tray according to the directions on the package.
  2. Sow the seeds as directed on each seed packet. If you’re planting lettuce, spinach, arugula, or other plants that are great for staggered plantings, then sow additional seeds every 10 to 14 days. That way, you’ll have veggies available for a longer period of time rather than all at once. Plant a few seeds per pot. It’s also a good idea to plant more seeds than plants you desire since some might not make it.
  3. Water well, without drowning the seeds. Place the cover on the tray.
  4. Leave the seeds to sit for a few days, checking every day to make sure the soil is still moist. When you start to see some green (how exciting!), set the tray cover aside.
  5. Set up the light about four inches from the soil surface. Move the light as the seedlings grow to maintain a distance of two to four inches between the light and the plants. Leave the light on 14 to 16 hours each day.
  6. Continue watering, so the soil is moist but not soggy.
  7. Once the seedlings grow their second set of leaves (which are true leaves—the first ones aren’t actually leaves but rather are called cotyledons), use a water-soluble fertilizer.
  8. After a few weeks, you’ll need to “thin out” the weakest seedlings, allowing space for the strongest ones to grow. Using clean scissors, snip the weakest seedlings below the cotyledons.

Transitioning the Plants to Outside

To make sure you don’t shock your plants, you have to gradually introduce them to the great outdoors. Once the risk of frost has passed, place the tray outside in a shady spot for about two hours, then bring it back inside. Repeat this the next day.

Then, on the third day, place the tray in the sun for about two hours. Repeat this each day, adding an hour of time outdoors daily. Once the plants are spending eight hours of time in the sun every day, it’s time for them to move outdoors for good! You can then plant each seedling in your garden, spaced apart at the proper distance according to the seed packet.

Gardening itself is so rewarding since you get to benefit from all the hard work you put into tending to your plants. And starting your own seeds only amplifies this feeling! Pick up any supplies you need for starting seeds at one of our SummerWinds locations in California.