How to Start Garden Seeds Indoors – Basic Technique

February 2, 2015 Updated: February 2, 2015

I can’t tell you how excited I am to start garden seeds indoors while there’s still a blanket of snow on the ground. Watching seeds germinate and seedlings grow, and looking forward to summer crops and beautiful blooms while the weather is dreary, brings life to an otherwise gloomy winter.

Aside from helping me to shake off the winter blues, seed starting is actually very practical for the gardener who grows large quantities of veggies, fruit and flowers. It also allows one a wider and tastier choice of plants than what you might find at your local garden center in spring (especially if that garden center is a box store). I grow hundreds of pounds of food every year, and I like experimenting with flowers. If I had to buy the same amount of seedlings as I start from seed, I’d go broke. Even when I factor in the cost of the seeds, grow lights, pots, organic fertilizer, and starter medium, I come out way ahead. Plus, I have the added benefit of knowing the source of my organic food, which didn’t travel more than a few yards from garden to table.

Supplies needed for starting garden seeds indoors

  • Flats or starter pots
  • Starting medium (not potting soil or garden soil)
  • Heat mat
  • Grow light/s
  • Small amount of balanced organic fertilizer
  • Vegetable, flower, or fruit seeds

Depending on your preference and how agile your fingers are, you can start seeds in flats (trays), or starter pots. If you use pots, choose plastic, because they’re reusable (in spite of the picture below). Pots made from biodegradable materials dry out quickly, taking surface moisture away from the seeds and seedling. If you’re not completely on top of your watering game, you’ll have dried out, dead seedlings pretty fast.

When it comes to what goes in the flats or pots, you must use a seed starting mix , not garden soil or potting soil. Seed starting mix is sterile and loose – no bacteria or molds are present, and the light texture allows for excellent root growth. This gives your seedlings a much better survival rate in the pot and in the garden.

heat mat isn’t absolutely mandatory. But if you’re starting seeds in a basement or otherwse chilly room, it’s highly recommended. A heat mat keeps the trays or pots about ten degrees warmer than the surrounding air, which encourages seeds to germinate much faster. You can buy a basic heat mat or super duper heat mat with very fine digital controls if you like to geek out.

Grow lights are essential – ignore all of the online articles which tell you to “place your pots in a sunny room or windowsill” (unless you have a solarium).  I don’t believe those writers ever started more than 3 seeds. Seedlings of all kinds need an enormous amount of light as soon as they germinate. Give it to them and they’ll flourish. If they sit on a windowsill, they’ll keep turning towards the window to absorb as much light as they can. This makes the seedlings “leggy” – lots of stem and few leaves – and makes for very weak seedlings. I started seeds this way the first year I did it, and it worked, but it was only a few tomatoes and herbs. Any quantity of plants larger than what can actually sit on your windowsill, and you’ll need grow lights. The size of your grow light – or how many you’ll need – is determined by how many seedlings you’re starting.

small amount of organic fertilizer is all your seedlings need until they’re transplanted. Literally a pinch is all I give them after they germinate, which is plenty.

Seeds (duh). Choose plants that can tolerate transplanting. This includes most vegetables and flowers, but there are some, like carrots and sweet corn , which don’t fare well when transplanted (unless you’re very experienced). A packet of seeds which will produce dozens of plants, costs about the same or less as one plant from a garden center. And you can save any extra seeds in a mason jar in your fridge for next year. But before you choose your favorites, do a little research and learn how many weeks before your last frost date the seeds need to be started. For instance, tomatoes are started about 8 weeks before last frost, but onions need at least 12 weeks before their set out date (which is usually a month before last frost – which means I start onions in mid-January). A little planning goes a long way – but don’t let it overwhelm you, it’s quite easy. Click here to learn the last frost date for your area.

To sow the seeds, fill your tray or starter pots to the top, and with your fingers, lightly press down on the starting mix. The pressure will reduce the mix by as much as 1/3rd, so keep doing this until the pot is filled to about 1/4″ from the top. Watering will eventually compress the mix if you skip this, but the weight of the water will make the mix sink, possibly depriving your seedling of space to grow sufficient roots. Sow two seeds per pot, or one seed 1/2″ apart in starter trays. Make sure your pot or tray is labeled with the seed planted there.

Johnny’s Selected Seeds has an excellent chart of when to start seeds.

Unless the seed packet specifies otherwise, lightly cover the seeds with more starting mix, but just enough to cover the seed – don’t bury them. Water the seeds with a mist – they only need a little moisture to germinate, not a bath. Also, too much water may lead to a disease called “damping off”, a fungal growth which may kill your seedling. Cover the pots, tray or flat with a plastic dome or clear plastic until the seeds germinate. This keeps the starting mix from drying out. As soon as the seeds germinate, remove the plastic to avoid fungal infection.

When the seeds have germinated, give them plenty of light, a pinch of organic fertilizer to help them grow (just once), and sufficient water. If started in trays, repot the seedlings after they grow their second set of leaves, to an appropriate size pot.

This article was written by Todd Heft, head administrator for This article is republished with permission, original article here.