Starting seeds indoors can feel daunting if you’ve never done it before, especially when pre-started seedlings are readily available at your local garden center. However, it’s relatively straightforward once you get the hang of it, and many find it rewarding to nurture plants throughout their entire growing cycle. 

If you’ve never started seeds before, here’s what you need to know about starting seeds indoors, plus some tips and tricks to increase your chances of success straight from gardening pros.

Gather Your Supplies

The first step in starting seeds indoors is to ensure you have the right supplies before you start. The last thing you want is to get halfway through the process only to realize you don’t have what you need.

Luckily, only a few things are required: seed starting mix, seeds, and a container. While you can buy seed starting trays and beginner kits with coir pods, you can also repurpose containers you already have at home. 

“You don’t need fancy equipment. Reuse a yogurt cup or an egg carton if you don’t have anything else,” says Valeria Nyman, chief product officer at Taim.io.

Seed starting mix, on the other hand, can’t be skipped. Regular soil is too heavy for delicate seeds, so investing in a good seed starting mix will make all the difference. 

Want more gardening tips? Sign up for our free gardening newsletter for our best-growing tips, troubleshooting hacks, and more!

Plant the Seeds

Next, it’s time to plant the seeds. Ideally, seeds should be started about six weeks before the last frost date in your area.

Fill the containers with your seed starting mix and plant the seeds according to the packet instructions. Then, mist the soil with water until moist but not soaking, and place the seeds in a warm, bright area. 

Provide the Right Conditions

Planting the seeds is just the first step. To prepare your seedlings for the garden, they need to be nurtured throughout the process. For seeds and seedlings sprouted indoors, this means providing the right amount of light, warmth, and water. 

Seeds require warm temperatures and consistent moisture to sprout, with ideal temperatures for germination ranging from 65 degrees Fahrenheit to 75 degrees Fahrenheit, says Carrie Spoonmore, co-creator of the From Seed to Spoon app.

Picture a warm, greenhouse-like environment. Once the seeds have sprouted, however, light becomes more important than maintaining warm temperatures.

“Use grow lights with a full spectrum (blue and red light) or in zones with sufficient winter sunlight; ensure your seedlings get at least 12 to 16 hours of light daily,” Spoonmore says.

At the same time, the soil should be kept evenly moist at all times. A spray bottle can be helpful when watering the seeds and delicate fresh seedlings. Once the seeds have sprouted, Spoonmore recommends switching to bottom watering to encourage strong root development.

Harden Off Before Transplanting

Your seeds have sprouted, and it’s officially warm enough to move the little seedlings outdoors. Except once you plant them, they all die immediately.

Does this sound familiar? If you’re getting stuck at the transplanting step, it’s probably because you aren’t hardening off your seedlings before moving them to the garden—a crucial and often overlooked step.

Hardening off is the process of acclimating delicate seedlings sprouted indoors to the relatively harsh outdoor conditions. It takes about a week, but it’s an essential part of indoor seed starting that can’t be skipped. 

“Transplanting seedlings too quickly to outdoor conditions can cause shock and stunted growth,” Spoonmore says. “Gradually introducing them to sunlight and outdoor temperatures ensures they thrive.”

Over five to seven days, slowly increase the seedling’s exposure to outdoor conditions, starting with a couple of hours of indirect light and increasing exposure each day. Once your seedlings can withstand a full day of direct sunlight in the location you plan to grow them, it is safe to transplant them to the garden bed. 

Seed-Starting Mistakes to Avoid

Naturally, you’ll make a few mistakes along the way, so if the fear of messing up is holding you back from trying, let this be your sign to take the leap and try anyway. 

“Seeds don’t come with a guarantee; they come with potential,” Nyman says. “Even if you mess up, you’re learning! Every seed is a leap of faith. Also, what is the cost of lettuce, a buck fifty a pack? It’s cheaper than therapy and way more fun!”

That said, watch out for a few common mistakes as you get started.

Starting Seeds Too Early

The excitement of spring approaching can make waiting hard if you’re itching to start your seeds. However, starting seeds too early is never a good idea. Seeds that are started too early will have to stay indoors for longer, which can negatively impact their development.

Also, larger seedlings are more challenging to keep alive indoors, making it more likely they’ll die before even making it to the garden bed. As hard as it can be, it’s always best to wait until the recommended time to start seeds indoors—typically about six weeks before the last frost date in your area.

Warmth for Seeds, Light for Seedlings

Starting seeds indoors can be split into two distinct phases: germination and the seedling stage. Germination requires warm temperatures and consistent moisture, whereas seedlings need lots of light and regular watering. 

“I’ve fried my fair share of seedlings by putting them too close to a heat source. Warmth is important for germination, but once they sprout, they’ll need light,” Nyman says.

Understanding the difference between these two phases can help you tweak growing conditions to give your seeds and seedlings the best chance of success. 

Improper Watering

Both overwatering and underwatering are common issues beginners can encounter when starting seeds indoors. It’s a delicate balance, but getting watering right is critical. Seeds need consistent moisture, but the soil should never be soaked. 

“Seeds want their soil just right, not too wet, not too dry,” Nyman says. “If it feels like a wrung-out sponge, you’re golden.”

This requires regular monitoring since seedlings absorb moisture quickly, especially when growing in small containers. Once your seeds have sprouted, you may need to water them daily to ensure they stay alive. A spray bottle or mister is a great way to water delicate seedlings without flooding the soil. 

Transplant Shock

Even if you do everything else right, failing to harden off your seedlings properly will lead to their eventual demise in the garden. Compared to indoor conditions, sunlight and temperatures outdoors are variable and require an adjustment period for all plants and seedlings. Taking the extra week to ensure your seedlings are acclimated to outdoor conditions will be worth it in the long run.