Starting Seeds Indoors

Growing a plant from seed to harvest is a rewarding challenge. Really! If you begin indoors, you can jumpstart the season while ensuring your seeds have the best possible growing conditions.

Follow these steps to start your seeds off right.

When to Start Seeds Indoors

One of the benefits of starting seeds indoors is that you can sneak in a longer season. This is fulfilling for eager gardeners but also ideal for certain plants that need an extended growing period to reach their full potential.

There is a sweet spot, however. If you begin too early, your seeds may outgrow their starter containers before you're able to transplant them. Most seeds can be sown indoors around 6 weeks before you plan to plant them outdoors. Check your seeds' packet, which should have information on when to plant based on frost dates. You'll also need to know your planting zone and watch your local weather forecasts to learn when the final frost of spring is in your area.

Keep in mind that not all seeds are suited to indoor growing, no matter when you start. Pumpkins, winter squash, cucumbers, corn, and root vegetables like beets, turnips, potatoes, and carrots are a few plants that prefer to stay where they're planted. Check the information that comes on the back of the packet or with the seed supplier you buy them from to know how your region matches up with your seeds’ needs.

What You Need to Start Seeds

• Seeds. It's what you're here for, so make sure you bring the seeds! Whether you're planting veggies, herbs, or flowers, seed starting offers you tons of planting options. Some suppliers offer a wide variety of seeds while others specialize in organics or heirlooms. Just make sure to buy a few more than you plan to grow. Not all of them will germinate (or sprout), so less is not more in this situation.
• Containers for growing seeds. You have plenty of options here. Whatever you choose to plant your seeds in, make sure your containers are at least 2 inches deep, and you'll want to clean them out thoroughly and poke drainage holes in the bottom (if they don't have drainage already).
• Seed starting trays are easy to find. It's best to choose one that's sturdy and preferably reusable.
• Try upcycled containers like yogurt cups, cottage cheese cups, egg cartons, or other plastic containers.
• Try biodegradable pots like peat pots or coconut coir pots. These can be planted along with the seedling when it's transplanting time.
• You can even try using eggshells or lemon rinds!
• Seed Starting Soil. Seeds need a soil that's light and fine so those baby roots can poke through. A good seed starting "soil" doesn't have much soil or dirt in it, if any at all. Instead, seed starting mixes contain lightweight ingredients like peat moss and perlite that allow for airflow and retain a uniform amount of moisture. Miracle-Gro® Seed Starting Potting Mix is a great option that's designed to nurture your seedlings.
• Labels. You know exactly what you planted…until you realize that seedlings all look the same. Save yourself a headache and use tape with permanent marker, colored labels, or small plant tags to remind you what you planted where.
• Cover. Using a plastic cover over newly planted seeds helps keep the moisture in the soil and humidity levels high. Most seed starting trays come with a cover, but you can also use plastic wrap, bags, or domes to cover containers. Just be sure your cover doesn't touch the soil and gives seedlings room to sprout. You'll also need to be able to access the soil to check moisture and water as needed.
• Light. While most seeds don't need light to germinate, some plants including lettuce, petunias, and begonias do need light to encourage them to sprout. Once any plant germinates, it needs plenty of light—-usually between 12 and 16 hours per day depending on the plant. Rooms with south-facing windows in your home are a great option, but even this may not be enough. Your seedlings may take on a leggy or spindly look as they're trying to reach the light. It's best to use LED lights, such as a shop light or grow lights designed for seed starting. Place your light above your seed containers to give your plants an even amount of light. You'll make your work easier if you find a light you can easily move up or down as your seedlings grow and use a timer to automatically switch the light off when it's bedtime.

How to Start Seeds Indoors

Once you've got your supplies, it's time to start planting. Follow these steps:

• Fill your prepared container with seed starting mix. It's best to add water to your mix to give it an even, consistent moisture before adding it to the container, but you can also water after you've filled your container.
• Add your seeds. Plant 3 seeds per container or tray cell since not all your seeds may germinate. Planting depth varies from plant to plant, so read your seed packet instructions carefully.
• Cover your plants with plastic wrap, bags, or domes and place them under a grow light.
• You'll want to keep an eye on the soil moisture. Use a mist spray bottle or gently water with a watering can if the soil starts drying out.
• Practice patience. Germination takes anywhere from a couple of days to a month depending on the plant variety. It's good to refer to your seed packet instructions to help gauge your expectations, and keep an eye out for little green shoots poking out from the soil.
• Once your plants germinate, remove the cover. You're looking for those two little leaves that every plant starts with (these aren't true leaves, but embryonic or seed leaves called cotyledons).
• Once your plants have at least one set of true leaves, it's time to prune. If multiple seeds sprout in one container or tray cell, use scissors to snip the less healthy or smaller plant(s) at the soil line. It's tough, but you'll be rewarded with a stronger, healthier plant.
• Care for your seedlings—they need warmth, light, water and daily attention—until they're ready to transplant. Keep the soil moist until plants develop at least one set of true leaves, then allow the soil to dry out in gradual increments as your seedlings continue to grow until the top ½-1 inch of soil dries out between waterings. Also, keep that light on and adjust the height if needed as the seedlings grow (your grow light's instructions should tell you how high above your plants your light should be).
• Refer to your seed packet instructions to know when it's time to transplant. Typically, this will be when your plant has a few true leaves on it or reaches between 4 and 6 inches tall.

Pro Tips and Techniques

Some seeds are perfectly happy inside their protective coat and aren’t keen to change it up. However, with a little prodding and careful encouragement, most will eventually join the seed-starting party. Whether they need to be scratched, chilled, or soaked, here are a few tips and techniques to get them stimulated. Check the seed packet to make sure it hasn't already been done for you.

Scarification.

Certain species are harder to germinate than others because their seed coats are resistant to water and oxygen, two of the essentials needed for sprouting. Give stubborn seeds—morning glory, lupines, milkweed—a boost by scratching them with a metal file or fine-grit sandpaper right before planting. This process, known as seed scarification, makes the seed's protective coating more porous. But now that it's been compromised, you'll want to plant it as soon as possible.

Stratification.

Seeds from plants that are native to temperate zones—regions that see mild winters—actually need a cold spell to germinate (strawberries, primrose, wild geraniums). You can simulate the season by chilling these seeds, or stratifying them. One common stratification method is to put protective peat moss in a plastic bag along with your seeds, and store them in the refrigerator at 39 to 41°F—make sure they don't freeze. Another way is to store the seeds in the freezer and pull them out to thaw a day before planting. How long you keep them chilled depends on the variety, but typically this is 4 to 5 weeks, or according to the directions on the seed packet label.

Soaking.

Another technique to speed up the germination process is seed soaking. This is popular for seeds like edible peas, sweet peas, parsley, beets, and chard, whose internal clocks rely on the moisture levels of spring to let them know it's time to grow. The process is simple: place your seeds in tepid water, generally for more than 4 hours but fewer than 24 (check the packet for instructions). Discard those that float to the top; they're usually considered bad for planting. Once their time is up, plant the seeds as soon as possible.

Sow Much Fun

So, your seedlings have sprouted, and you're a proud plant parent…now what? Next, you get to transplant them to their permanent homes. Follow this guide to transplanting seedlings to give your new plants the best chance at success.

While sowing seeds indoors requires a commitment, the process is worth it. You'll have more bonding time and greater control over your plants’ happiness. Most of all, though, it's fun to discover and grow plants that you might not find at your local nursery. So dream big, and go for it!

Are Miracle-Gro Indoor Potting Soils Sustainably Sourced?

We prioritize corporate integrity and responsible product sourcing across our global supply chain. Through our environmental partnerships, we help protect biodiversity and preserve vital resources. Scotts Miracle-Gro relies on community engagement to evaluate the positive and negative impacts of its operations and to maintain strong relationships. By carefully managing our raw material sources, we aim to reduce our environmental impact. We use widely accepted sustainability reporting standards to collect and analyze our environment data.