How to Start Seeds Indoors to Jumpstart Your Spring Garden

Test Garden Tip: Look on the seed package label to find the number of weeks you're supposed to start seeds indoors before the average last frost date. It usually takes about six to eight weeks to give your seedlings a head start on spring, so count backward from your area's frost date to figure out when you should start your seeds indoors.

Container Options

Plastic seed trays ($16, The Home Depot) and seed-starter kits ($16, Etsy) are super easy for growing seeds indoors. But you can dig through your recycling bin, too. Just remember to punch a drainage hole in each container before planting. Cardboard egg cartons work well, but you can also repurpose items such as clean, cut-down milk jugs and yogurt cups. Or, you can make your own seed starter pots from newspaper.

How to Start Seeds Indoors

Even though the planting instructions on the packet might vary, you'll need the same supplies to start any seeds indoors. Here's what you'll need:

• Seed-starting pots with drainage holes (or DIY seed starting pots)
• Seed-starting mix ($7, Target)
• Labels for each pot ($3, The Home Depot)

1. Fill up the pots.

Fill pots with fresh, moistened seed-starting mix. Don't use garden soil, which is too heavy and may have insects or diseases in it. Leave about a half-inch of room to the top.

2. Sow seeds.

Follow the seed packet instructions for planting. Some will suggest making a shallow hole in the center of the potting mix to put the seeds in and others will say to add seed right on the surface. It's best to add 2-3 seeds to each pot, in case one doesn't sprout. Use the crease of the seed packet or place seeds in a creased piece of paper to help direct the seeds where you want them to go.

3. Add water.

Once you've sown the seeds, mist each container enough so that the potting mix is damp, but not drenched with water. The water will also help the potting mix settle around the seeds.

4. Label and cover.

Label each of your pots so you know what's growing in them. Loosely cover the pots with clear plastic wrap or zip-top bag, which helps maintain humidity and warmth.

5. Keep pots warm and watered.

Place your seed pots in a location that's warm and free of drafts, but not in direct sun. The top of a refrigerator works well because it's out of the way and it gives off just enough heat around it to help the seeds grow. The ideal temperature is about 75°F but no hotter than 90°F. Once the tiny seedlings emerge, remove the cover and move them into a sunny window. They need about 12 hours of light a day, so supplement with grow lights as necessary.

Caring for Seedlings Indoors

You started your seeds. Their first leaves are poking up in the pots. What do you do next?

1. Give them some air.

After seeds have sprouted, take off the plastic wrap or other covering so they can have room to grow.

2. Thin the seedlings.

As the seedlings make their presence known, they need their space. Keep the ones that look healthy and strong, and snip the rest so there's just a single plant per pot.

3. How to repot seedlings.

After they're about two inches tall and have a couple sets of leaves, your seedlings need an upgrade. Transplant them into larger containers, this time in regular potting mix instead of seed-starting mix.

4. Mist seedlings.

Don't let the seedlings dry out! Misting them is the best way to give them a drink. Don't put them under a faucet or hose, because the water pressure can wash them right out of their containers.

5. Harden off seedlings.

Before you can move your seedlings out into the garden (keeping your frost-free date in mind), you need to give them a few days to slowly get used to life on the outside. That's what's known as hardening off your plants. To do this, place the seedlings outside for a short time in a protected spot (about an hour or two). Each day, increase the length of time you leave them outside until they can remain outdoors all day.

Indoor Seed Starting Problems

Sometimes, you might notice your seedlings struggling. Here's a couple of common issues to watch out for and what you can do to avoid them:

What causes leggy seedlings?

Not enough light can result in spindly, stretched out seedlings (like the pea seedlings shown above) that are desperately trying to find more brightness.

Solution: Use a grow light or move your plants into a better lit spot.

Why do seedlings suddenly wilt?

Wilting seedlings might be a sign of damping off, which is caused by a fungus that sometimes appears because of overwatering or overcrowding. Or you may see tender young leaves wilting when soil gets too dry.

Solution: Make sure you use fresh seed-starting mix that has been sterilized to kill any fungi or bacteria. If potting mix feels dry to the touch, mist with water and check back later in the day to see if your seedlings have perked up.

Starting seeds indoors will let you have a lush, beautiful garden for a fraction of the price of picking up new plants at your local garden center. After the last frost of the season has passed, your seedlings should be ready to go out into the garden. If you're successful, you'll soon have healthy, towering plants that look nothing like the tiny seeds they came from.