Planting from seed is a gratifying process, but certain seeds require a longer growing period than the length of summer in your region for a successful garden. Seed starting inside gives you a jump on the growing season so your plants have enough time to mature and flower or produce fruit before the first frost. Follow this guide to learn how to start seeds indoors.

Choosing the Right Seeds

Before you start buying seeds, you'll need a growing plan. If you plan on growing perennials, first, determine your garden growing zone and learn which plants will thrive in your region — most annuals can be grown in any zone. Next, consider your garden's conditions. How large is your space, and how much room will those seeds require when they grow into mature plants? How much sun does your garden receive throughout the growing season? Most vegetables and many ornamental flowering plants need at least six hours of full sun daily. You'll also want to review the recommended growing directions for the specific seeds you have in mind. Certain crops don't transplant well and do best when sown directly. Keep these points in mind as you decide which varieties to buy for seed starting to help ensure a thriving garden.

What You Need to Start Seeds

• Planting trays or pots: Plastic trays with cells you fill with soil and seed are the pro grower’s choice because they can hold a lot of seedlings and they work well in self-watering systems. They come in a range of 16, 36, or 72 cells. Fiber pots are a better option for larger or faster growing seeds. They’re made of wood fibers, are fully biodegradable, and go into the ground along with the seedlings, reducing transplant shock when they move into the garden.
• Soil-less mix: Ordinary garden soil or even potting mix are too heavy for starting seedlings. The ideal medium is not soil, but rather a material that’s light and well-drained, but capable of holding just enough moisture for the tender little plants. Gardeners have long used peat as the primary medium for seed starting, but there are concerns about the sustainability of peat bogs. Today, you can use coconut coir, a byproduct of processing the fruit’s shells, which has the same properties. Bricks of Organic Coconut Coir are inexpensive and easy to use.
• Plastic cover: One of the keys to germinating seeds is keeping the medium consistently damp so the emerging rootlets can begin soaking up moisture. A plastic cover traps in the humidity while you wait for the first sprouts to come up.
• Water tray: Maintaining those constant moisture levels is critical to success with starting seeds indoors. The Burpee 36 and 72 Cell Greenhouse Kits come with everything you need, including a handy reservoir tray you keep filled with water. The seedlings drink it up as needed, so you don’t have to check them every day.
• Heat mat: Most vegetable and annual flower seeds germinate more quickly indoors when they’re kept a little warmer than room temperature. The Burpee Seed Starting Heat Mat evenly warms the soil to the ideal temp, and it’s water resistant so it’s safe to use with seedling trays.
• Grow light: Seedlings such as tomatoes, peppers, and many others need direct light to grow vigorously. If you don’t have a sunny windowsill that is big enough to hold your trays, you can give your plants supplemental light from LED fixtures. Burpee offers several different sizes and styles that provide lots of light but stay cool so your plants don’t burn.
• Labels: Just about every experienced gardener can tell you about the time they forgot or didn’t bother to label their seedlings and had to wait for them to mature to know what they had planted and when to move them outdoors. Don’t let that happen to you—or let it happen again, if it already has. Mark your trays with tags like Burpee Plant Labels every time and you’ll never have to guess.

Deciding When to Start Seeds

Deciding when to start seeds indoors will depend on the seeds you select and your growing zone. Check the seed packets for "days to germinate" and how many weeks of growth each variety of seedlings needs before being transplanted to the garden. Then, count backward from your area's last frost date. You don't want to start too early, or your seedlings may grow weak and leggy.

How to Germinate Seeds

Seeds contain everything they need to sprout once they are in the soil and absorb moisture. Your role is to give the seeds ideal conditions so that they get off to a healthy start.

Begin by checking the seed packet to see how deep each variety needs to go. Some seeds require light for germination and should be sprinkled on the soil surface. Other seeds may need to be buried under 1/8 to 1 inch of soil, depending on their size. Carefully follow the packet directions for planting depth.

Moisten the seed-starting mix before planting so that you don’t wash out tiny seeds.

Experienced gardeners plant two seeds per cell or pot for insurance. If both seeds germinate, snip off the weaker one so the other can grow stronger.

Cover the tray or pots with plastic wrap or a lid to trap humidity and keep the planting mix consistently moist as they germinate. Once the first few seeds have germinated and you see leaves, remove the cover to allow air to circulate.

Bottom warmth of 75 to 85 degrees F helps seeds germinate. A heat mat gently warms the soil without overheating it. Set your tray on the heat mat and move it off when the majority of the seeds have sprouted.

When do you start seeds indoors? Find out your average first and last frost date from your county extension service. Use that date and the days to maturity indicated on the seed packet to determine when is the ideal time for each type of plant.

Burpee’s seed-starting kits and trays make it easy for you to learn how to germinate seeds. Enthusiastic home cooks and people with limited space will love the Culinary Herb Windowsill kit. It comes with cilantro and Single Italian parsley and a reusable eight-cell planting tray.

The 36-cell Superseed Starting Tray works well for starting vegetable, flower, and herb seeds. It’s made with food-grade silicone cells that cradle seedlings and gently pop out to reduce stress during transplanting. The deep channels in the watering tray draw excess away from the seedlings, helping protect their health. The tray is dishwasher-safe, so you can use it for many seasons to come.

Getting Seedlings Ready for the Garden

Transplanting to Roomier Containers

Before planting in the garden, some seedlings may need more room to develop strong root systems. Moving them to larger pots can provide the space they need to grow. Use the same growing mix as for seeds. Handle the  baby plants gently by their leaves—not the stems or roots and try to keep the tiny rootballs intact as you move them to their new pots. Create a small hole in the moistened mix, place the seedling, and gently press the mix around it. Water as usual, ensuring plenty of light and gentle air circulation.

Acclimating to Outdoor Conditions

Once seedlings have developed in larger pots, they need to be gradually adjusted to the outdoors—a process known as hardening off. Begin by placing them in a sheltered, shady spot for a few hours each day, gradually increasing their exposure to sunlight over the following days. Keep the soil consistently moist, as small pots will dry out quickly in outdoor conditions. After a week to 10 days, the plants should be ready to be transplanted into the garden. Be sure to watch the weather for any frost predictions and choose the right time to start the process.

To learn more about starting seeds, check out more of Burpee's guides to seed starting.

Learning How to Start Seeds Indoors
Plant seeds according to packet directions. Label each container with the plant name, variety and sowing date, then loosely cover the container to hold in humidity while allowing for air circulation. Bottom warmth (75 to 85 degrees Fahrenheit) helps seeds germinate. Set trays on a seedlings heat mat to generate consistent temperatures. Once the seeds have sprouted, you can remove the cover. Keep the soil moist but not soggy.

After the seeds germinate, they need light. A sunny south-facing window works best. If you don't get enough natural light, use a grow light for 16 hours a day. Position the lights 3 to 4 inches above the seedlings, and adjust upward as the plants grow.

Transplanting Your Seeds
Some seedlings may require transplanting into larger pots to give them room to grow and develop their root systems. Use the same growing mix as for seeds. Handle the baby plants gently by their leaves, not stems or roots, and try to keep the tiny rootballs intact as you move the plants to their new pots. Poke a hole in the moistened mix with your finger, place the seedling in the hole and gently pat the mixture around it. Water as before, and provide plenty of light and gentle air circulation.

Hardening Off Plants
Young plants require hardening off before you can transplant them into your outdoor garden. That means gradually adjusting them to the outdoors by setting them out in a sheltered, shady spot for a few hours each day, increase the time and light exposure. Keep them watered, as small pots will dry out quickly outdoors. After a week to 10 days, plants should be ready to be transplanted into the garden. Be sure to watch the weather for any frost predictions and choose the right time to start the process.

Starting seeds indoors allows you to enjoy a thriving garden no matter where you live and how long your spring and summer seasons last. It also expands your growing possibilities, as more varieties of seeds are available than young plants for sale.

To learn more about starting seeds, check out more of Burpee's guides to seed starting or