How to Start Seeds Indoors

Starting seeds indoors can help you get a jump-start on spring! Learn what you need and get tips for successful seed starting here.

Believe it or not, even the most experienced gardeners are often hesitant to start seeds indoors. The process does take some time and planning, but once you create a good seed-starting setup, you’ll be able to grow flowers and veggies not available at your local nursery!

Start Seeds IndoorsLeroy (hopscotch)
No need to spend a lot of money when starting seeds indoors – the best setups are simple!

Create a Seed-Starting Setup

Location

Choose a place for your seed-starting setup that is safe from kids and pets, but where you’ll be able to easily access them each day. Basements, spare rooms, or kitchens are often good places; make sure you’ll have ready access to water and protect surfaces that could be damaged by soil or moisture.

Containers

The possibilities for seed-starting containers seem endless. You can buy ready-made growing kits to start seeds indoors that include trays, soil, and covers to provide moisture (I really like the BioDome from Park Seed), but you don’t need to spend a lot. You can start seedlings in plastic trays, peat pots, even eggshells! It’s usually best to start seeds in smaller containers, like the divided trays you’ll find for sale, since it allows more control over watering and helps them to develop compact root systems as they start growing.

Soil

You can use the potting medium provided with some seed starting kits (follow the directions to hydrate the disks into usable soil), or purchase a sterile seed-starting mix from your local nursery. Don’t use old potting soil you have sitting around from previous years or dirt from your outdoor garden, as it may contain unwanted old seeds or pests.

Starting Seeds IndoorsGayle (cove2700)
A simple shop light propped on supports will provide the light you need to get started.

Light

You’ll be most successful if you have bright light available for most of the day (12 – 16 hours). This isn’t usually something you can get just from a sunny windowsill, especially since late winter and spring are apt to be cloudy more often than not. You’ll find it’s worth it to make the investment in some fluorescent growing lights that can be kept at an optimal distance from your growing seedlings.

Water

Seedlings need consistent moisture, since they haven’t yet developed root systems and leaf networks to help them store it in dry times. Watering from above can be damaging to newly-sprouted fragile stems, so the easiest way to give seedlings the water they need is with bottom watering. Set your containers into a tray holding a few inches of water, and add more when the tray dries out.

Temperature

Many seeds need ideal soil temperatures before they will germinate and begin to grow. Starting seeds indoors allows you to control the soil temperatures and get a head-start before the ground outdoors is ready, but if you’re working in a basement or garage, you might need to provide a little extra heat to help them along. Gardeners have developed a variety of tricks for this, including placing the plants on top of the fridge (really!) or using a heating pad underneath the water tray. You can also buy specially made heating elements for seed starting, if you prefer.

Starting Seeds Indoors Thinning
These seedlings all look healthy, but there are too many in one cell. It’s best to thin them to one or two plants so they can develop strong root systems.

Getting Started with Seeds

  • Your soil or potting medium should be damp, though not soaking wet. Fill your containers about three-quarters of the way, and press the soil flat and level (don’t compress the soil too much, though).
  • Empty the seeds from the packet into a small bowl. It’s much easier to control the seeds this way. Save your seed packets for future reference as the plants grow. (Try using a coupon organizer to keep your packets all in once place.)
  • Large seeds like zinnias or marigolds are easy to plant with your fingertips, but smaller seeds can be a little tricker. Use tweezers or even a small pipette to help you handle tiny seeds.
  • If you’re using a divided container with lots of small planting areas, plant just 2 – 4 seeds per section. If you’re planting in larger flats, make little furrows and try to space the seeds evenly, no more than an inch apart.
  • Follow the directions on your seed packets to determine how deep to sow the seeds. Some should be covered with a light layer of soil, while others will need to lay directly on the surface to germinate.
  • Once all the seeds are sown, cover with a layer of plastic wrap (or use the lids that come with some growing kits). This will keep the soil from drying out, and hold in heat as well. Remove the plastic wrap as plants begin to grow, and make sure they have adequate air circulation to avoid fungal growth, known as “damping off” (see “Troubleshooting” below).
  • Don’t forget to label! Many seedlings look alike, so grab a handful of popsicle sticks and a permanent marker and mark your rows by type. You may also wish to note the date, especially if you’re starting a variety of seeds at different times.
  • You’ll need to check your seedlings daily, since it’s vital that they don’t dry out. Add more water to your bottom tray as needed. You can also mist the seedlings with a spray bottle, but don’t overwater.
  • The first round leaves that appear from each seed are called cotyledons. Soon, the plant will form its first “true leaves”, which are likely to be different in shape. Once you see these leaves, it’s time to thin your plants to remove any weaker seedlings by using a small pair of scissors to snip them off at soil level.
  • When your outdoor soil and weather conditions are right (check the back of your seed packets for info), it’s time to “harden off” your plants by moving them outdoors and gradually exposing them to more sunlight. Within a week or two, you’ll be ready to transplant them into your garden.
Start Seeds IndoorsLeroy (hopscotch)
Watch the weather carefully. Bring seedlings back indoors if the temperature drops dramatically or hard rain is predicted.

Learning to start seeds indoors is just like anything else: you’ll have some successes and some failures, and you’ll learn a lot along the way. Start slow and be sure you can devote daily attention to your seedlings. Don’t be afraid to experiment, and keep a journal to document your ups and downs from year to year. Most gardeners find that once they really get going, the urge to start seeds indoors is pretty addictive – and very rewarding!

Looking for more details about starting seeds indoors? Check out this article for additional Seed Starting Basics.

Jill Staake
Jill lives in Tampa, Florida, and writes about gardening, butterflies, outdoor projects and birding. When she's not gardening, you'll find her reading, traveling and happily digging her toes into the sand on the beach.