How to Grow Seeds Indoors

Starting seeds indoors doesn't have to be daunting—in fact, it's a rewarding, economical, and enjoyable way to bring vibrant life to your garden. Whether you're growing savory herbs, colorful flowers, or nutritious vegetables, beginning your seeds indoors offers numerous benefits, including cost savings, greater variety, and stronger plants.

Benefits of Starting Seeds Indoors

• Economical: Starting plants from seed is far less expensive than purchasing grown plants from nurseries.
• Greater Variety: Gain access to rare, heirloom, and specialty plants not typically available at local garden centers.
• Year-Round Gardening: Enjoy fresh herbs and beautiful blooms even in the depths of winter by starting your garden indoors.

• Starting seeds indoors can save money, provide greater variety, and be a lot of fun.
• Starting an herb garden indoors means you can cook with fresh herbs in the middle of winter.
• We’ll show you how to determine when to plant your indoor garden and when you can move the plants outside.
• Hardening off your plants that have been grown inside is necessary to a successful move to your outdoor garden.

Gardening indoors is not only fun, and certainly helps beat the winter blues, but it also can benefit your pocketbook. A package of seeds can provide many more plants than you could purchase for the same amount of money.  The biggest advantage is the access to so many more varieties. 

Let’s just look at the tomato as an example. When you go to your local garden center to buy a tomato plant for your garden, you may find only two or three varieties of regular tomatoes. They may also have a variety of cherry tomato, and maybe a yellow tomato. That’s it.

Now, check the tomato section of a great seed catalog like Park Seed. There are pages after pages of tomato varieties to tempt you. There are tomatoes that are the perfect size for growing in a pot and others that are going to grow to be the centerpiece of your garden. Some tomatoes are perfect for canning or freezing, or creating the perfect salsa.

Then they have heirloom tomatoes. Have you ever wondered what your great-grandparents grew before hybrids were developed? How about these varieties: Mortgage Lifter, Black Krim, Cherokee Purple, or Green Zebra tomatoes? Just the names make you want to try them. Every tomato you grow will taste so much better than what you buy in a grocery store.

Try Flower and Herb Seeds

Starting seeds doesn’t have to be limited to vegetable gardening. You can also start flowers. There is a huge variety of flowers available in seed. While many can be sown directly in the soil, why wait until the middle of summer before you see the actual flowers? By starting your seeds indoors, you will have flowers blooming in your garden much earlier.

Do you love the color purple? Do you want your garden to be a wonderland in shades of purple? Start seeds of purple and lavender petunias for the sunny areas and Impatiens to plant in the shade. Use your favorite colors to decide what to plant.

Another indoor garden option is an herb garden. The great thing about an herb garden is that you can use the herbs while they are happily growing on your windowsill. Then, when summer comes, move them outside and continue to enjoy them. Having fresh herbs all winter makes the food you prepare that much more flavorful. Seeing green plants growing lifts your spirit during the long winter months––and don’t forget to just rub the leaves. The scent of fresh basil or mint has to make you feel good. Herbs are definitely a multi-sensory feast!

What They Need

So now that you are convinced that indoor gardening is worth a try, how do you proceed? There are several things you will need to provide for your seeds to grow. They need a growing medium, they need water, and they need nutrients. They need light to grow, and they need a warm spot. They’re pretty needy, and you are their new caretaker.

Here are the steps for starting seeds:

1. Choose the container. Seeds can be started in many types of containers. If you prefer biodegradable options consider peat pots, expandable peat or coir pellets, or pots made from composted cow manure. If you prefer plastic pots there are options from 3 inch pots to multiple sizes of 6 packs. Our favorite way to start seeds is the Bio Dome. More on the Bio Dome to come.
2. Growing medium. Generally speaking, you will be more successful if you use a soilless mix to plant your seeds in. The tiny fragile roots sometimes have trouble getting through actual soil. You might be able to use the pellets that expand when you add water. Once they are expanded, you can plant one or two seeds in each.
3. Watering. Bottom-water your seedlings. Adding water on top of the seedlings encourages damping off. Pathogens attack your seedlings at the soil level, causing the stem to rot and kill the plant. You can help prevent this by bottom-watering. Cover your pots or place them in a plastic bag to keep the humidity stable until they germinate. As soon as they have germinated, remove the plastic to allow air circulation.
4. Light. You will need to provide 12-14 hours a day of light for your seedlings. More is better. You will have to use grow lights, either LED or wide spectrum fluorescent. Position the grow light several inches above your seedlings and raise it as the seedlings grow.
5. Heat. Some seeds like to be warm to germinate. Refer to the seed packet for which seeds need heat. The best and easiest way to provide the warmth they require is with a heat mat. Just place the mat under your tray of seed starts, and you’re set.  

Your System or Ours

Starting Seeds Indoors with Park Seed's Bio Dome Seed Starter Kit

The easiest, most effective way to ensure seed-starting success indoors is with Park Seed’s innovative Bio Dome Seed Starter Kit.

Why Bio Dome?

• Perfect Environment: Combines humidity control, consistent moisture, and ideal temperature.
• Bio Sponges: Promote deep, healthy root development with their unique, sterile design.
• Bottom-Watering Tray: Reduces overwatering and mold risk by delivering moisture directly to roots.

How the Bio Dome Components Work Together

The Bio Dome integrates three essential components:

• Clear Dome: Provides adjustable humidity, creating ideal germination conditions.
• Bio Sponges: Engineered sponges that absorb the optimal amount of moisture, preventing waterlogging while encouraging strong root growth.
• Planting Tray: Ensures consistent moisture distribution, enhancing germination rates.

Common Seed-Starting Mistakes and How to Fix Them

• Overwatering: Leads to mold growth and damping-off disease. Solution: Use bottom-watering systems like the Bio Dome to regulate moisture.
• Insufficient Light: Causes weak, leggy seedlings. Solution: Use supplemental grow lights and keep seedlings 2-4 inches beneath lights.
• Incorrect Timing: Planting too early or late can weaken plants. Solution: Consult the From Seed to Spoon app for precise scheduling.
• Temperature Extremes: Seedlings may fail to germinate or wilt from incorrect temperatures. Solution: Use seedling heat mats and monitor with a thermometer.

If you want to grow herbs to use throughout the winter, you can start them in the Bio Dome. Once they have a couple of sets of true leaves, transplant them into a pot.

Grow Your Own from Scratch

When deciding to start seeds indoors, it can be difficult to choose which plants to grow. Unless you have unlimited space with lots of light, you will have to be selective. Choose plants that you can’t get at your local garden center. A good choice would be a flower, vegetable, or herb that you have trouble finding in the spring—like Stevia or Fragrant Corkscrew Vine. Another consideration is if you need a certain color for your garden. Also, if you need a large amount of one kind of plant, you might want to start the seeds indoors. Plants that need a longer growing season are also a good choice for your indoor garden.

Start Them Off Indoors

Typical vegetables that are started indoors include tomatoes, peppers, broccoli, cauliflower, and cabbage. Also, you could start eggplant, squash, and cucumbers. Lettuce and spinach are both cool-weather plants. They like to grow in cool weather, but they don’t like to germinate in cool soil. So, start some of each indoors if you want an early harvest and plant the rest of your spinach and lettuce a little later directly in the garden.

Most of us can plant greens and corn directly in the garden but, if you live in the far north, you may have to start your seeds indoors to give the plants the time they need to mature.

So, how do you know when to start your seeds? The first thing you need to know is which planting zone you live in. This will give you the approximate date that you can plant outdoors in your area. Then read the back of your seed packet. It will tell you how many days they take to germinate and how long until you can harvest your vegetables. Now, count backward to determine when to plant.

The majority of plants will need about six weeks from planting to moving outdoors. There are seeds that will need to be planted as early as January or February, though, so check the package for sure.

Ideally, you will start your seeds indoors and not have to transplant them until they are ready to move into the garden. But life happens. Maybe the spring is colder than usual, or it seems to rain every other day and the garden is too wet. If your plants are outgrowing their root space, you may have to transplant them into larger containers before you can move them outdoors.

When to Move Them Out

You do want your plants to have at least two sets of true leaves before they’re moved outdoors. If everything is seeming right for moving the plants, they will need to be hardened off. Hardening off is the transition time given to plants to get used to being outdoors. In your house, the plants have never been in the wind, and the temperature has remained constant.

Suddenly, the temperature changes and there are cool nights and warm days. There is wind blowing them and rain will fall on them. Add to that, the sun is much more powerful than any light. So, your plants will need time to adjust. Move them outdoors into a sheltered area with filtered light, starting them out for just a couple of hours. Gradually increase the amount of time they are outside and expose them to more sunlight. Make sure they don’t dry out and, in a few days, they will be ready to be placed in their permanent home outdoors.

Above All, Enjoy the Process—They Grow Up So Soon

Have fun with this! You may have some failures, but you’ll learn from your mistakes and do better next time. Keep a gardening journal. Write down what seeds you started and when. Keep track of when you are able to plant outdoors. Keep track of what works and what you want to change next time. It really helps, and each year you will improve as a gardener and as a baby-plant parent.

FAQs for Indoor Seed Starting Beginners

Q: How deep should I plant my seeds?
A: Typically, plant seeds twice as deep as their width. Tiny seeds that require light to germinate should remain uncovered or just lightly pressed into the surface.

Q: When should I remove seedlings from the Bio Dome?
A: Once seedlings have their first true leaves and reach 1–2 inches in height, remove the dome to increase airflow.

Q: Why aren't my seeds germinating?
A: Common causes include overly wet or dry conditions, incorrect temperature, or insufficient lighting. Adjust these factors according to your seed packet instructions.

Q: How long does it take seeds to germinate indoors?
A: Typically, seeds germinate within 5–14 days, but this varies by species. Refer to your seed packet for specific timelines.

Using Bio Sponges in Non-Traditional Setups

• Greenstalk Towers and Vertical Gardens: Bio Sponges fit perfectly into vertical gardening systems, ensuring efficient root development in limited spaces.
• Growing Bags and Containers: Directly transplant Bio Sponges into containers or grow bags for seamless transition without root disturbance.
• Hydroponic Systems: Bio Sponges provide an ideal sterile medium for hydroponic setups, supporting rapid germination and vigorous growth in water-based environments.