Everything You Need to Know About Starting Seeds Indoors (2024)

While a trip to the garden center in early spring to pick out plants is hard to beat, it's even more rewarding to grow your very own seedlings! Whether you want to produce gorgeous flowers or grow a vegetable garden, learning how to start seeds indoors is a great way to save money. Although it requires some work, you’ll be able to plant the specific varieties you want—plus, it’s fun and satisfying to watch your plants grow from just a few seeds! Starting your seeds indoors also gives you a head start in places of the country where the growing season is short. For example, if you're growing tomatoes or peppers which are heat lovers, they can’t go in the ground until all danger of frost has passed in your region. By starting them indoors, your plants will have plenty of time to mature and harvest before the weather returns.

So, whether you want to plant gorgeous types of roses to spruce up your landscaping designs or you want to try your hand at growing a wide array of veggies, these tips on growing seeds indoors will be so useful! You'll find out the best time to start, what plants shouldn't be started inside, and how to transfer them into your garden when the time comes.

What's the best time to start seeds?

Starting seeds is a process, so you can’t wait until the last minute. It takes two to 12 weeks to grow a plant big enough to then plant in your garden. To determine when to start your seeds, you should first check the last expected frost date in your area. Unsure of when that is? You can find that information through your local university coop extension service (find yours here). The date is an estimate based on past years, but it'll give you a good idea of when to start your seeds so they'll be ready to plant at the perfect time.

Most plants should be started at about six to eight weeks before the last frost date. Or, you can check out a handy seed starting schedule to do the work for you.

Wait—are there seeds I shouldn't start indoors?

Some seeds shouldn't be moved after planting. There are several types of vegetables and flowers that will do better if seeded directly into your garden, rather than started early in pots. Many of these include root crops like radishes and beets, beans, carrots, corn, peas, and some types of squash such as zucchini.

What's the best container for planting seeds?

Practically any container with drain holes is fine for starting your seeds. You even can recycle containers like clean yogurt cups to use as pots. Just make sure they’re at least two to four inches deep with holes poked in the bottom. Peat pots or compartmented starter trays with a plastic cover will also work well—the lid makes them act like mini greenhouses! Then, fill pots or compartments about 3/4 full with a specially-formulated seed-starting mix—not potting mix, bagged top soil, or garden soil, which may contain diseases or weed seeds.

Okay, so what's the best way to plant the seeds?

Press the seeds into the surface of the soil, usually about 1 1/2 times as deep as the seed’s size. The seed package also will tell you how to deep to plant the specific variety (Hint: It’s usually not as deep as you’d think!).

Once planted, mist lightly, then cover with plastic wrap or the cover that came with your starter tray. Don’t forget to label everything so you know what’s coming up!

How much sun should I give my new seeds?

A south-facing window sill may be your first choice to place your pots, and it will work—but you run the risk of growing weak plants that stretch for the light. There may also be cold drafts at night, which your growing plants aren’t going to like. Besides, seedlings need 12 to 14 hours of light per day to grow strong and bushy, and northern climates don’t receive that much sun in early spring.

For the best results, invest in an inexpensive fluorescent or LED grow light on a stand or chain so it can be adjusted as the plants grow. Make sure to set it up in a room where you don’t sleep because it’s super bright! You'll also want to use a timer because plants need periods of darkness too. Initially, place the light two to four inches above the soil, then move it up accordingly as the plant gets bigger. Maintain that gap between the light and the plant to encourage healthy growth. Also, once the seedlings germinate, remove the plastic wrap or greenhouse cover.

How do I make sure my plants are healthy?

Soil-less mixes are best for starting plants to prevent disease, but they contain few nutrients. So, once the second set of leaves appear on your seedlings, water with a half-strength solution of liquid fertilizer about once a week. Let the plants dry out a bit in between waterings so you don’t develop damping-off, a common fungal disease that causes seedlings to collapse. Make sure to water from below too, by letting the pots soak in a tray for a few minutes.

When is it time to plant seedlings in the garden?

About a week or two before it’s safe for your seedlings to go into the garden, start the process of “hardening off.” This means you slowly acclimate your seedlings to outdoor conditions by placing the pots outside in a protected area from wind, and giving them longer doses of sunlight each day. Once you've done this, then you can plant and enjoy!