How to Successfully Start Seeds Indoors, According to a Pro

With spring right around the corner, it’s time to start getting excited about outdoor gardening. Whether you already know exactly what you want to grow in your garden, or you’re testing your green thumb for the first time, it can be easy to feel overwhelmed or get carried away. The best plan is an early one, especially when it comes to starting seeds indoors.

Many people start seeds indoors while the weather is still too cold and then replant them outside once the final frost has passed. If you’re looking to do this, there are several things you can do to ensure that your seeds sprout successfully and are ready for your garden once the temperatures warm up. We spoke with a few gardening experts to get the very best tips for you. Even pros might learn something new.

Do Your Research

“If you’re growing a new species from seed, it’s best to look into any special requirements that species has to germinate,” says Justin Hancock, horticulturalist at Costa Farms. There are some seeds that may prefer to be exposed to cold temperatures to sprout (milkweeds are like this). Others may germinate more quickly with lots of light or even scarification (i.e., weakening or opening the seed coat that protects the seed).

“If you’re buying seeds from a retailer, they’ll often come with instructions that provide their specific needs,” says Hancock. “But if you’re sowing seeds you’ve collected or that have been shared with you, knowing their requirements can greatly speed up the process and improve your success rate.” Hop online and do a quick search to make sure you’re treating your seeds right or consult with the person who shared the seeds with you what they’ve done in the past for success.

Use a Seed Starting Mix

“Garden soil is generally too compacted and too heavy for tiny seedlings, which require a fluffy, well-drained growing medium to develop strong roots,” says Lindsay Miller, an expert at Gardener’s Supply Company. “Garden soil can also host pathogens or other diseases that can easily kill little seedlings.”

Instead, opt for a seed starting mix. It’s important to check the ingredients of potting mixes if you’re not making your own. Look for things like vermiculite or perlite which help with drainage. If you want a sustainable alternative to peat, look for mixes that contain coco coir.

Provide Plenty of Light 

“Seedlings are hungry for light,” says Miller. “If you have a very bright south-facing window, you may have success with seedlings that don’t need to spend much time indoors and can be transplanted early in their growth, such as pumpkins, cucumbers, and morning glory.”

Take advantage of that strong natural light and try to sow as many seeds as you can in the space you have.

But if you aren’t blessed with bright, south-facing windows, don’t worry. You can still start your seeds indoors, but you’ll need to get some artificial grow lights. There are many to choose from, and they’ll ensure your seedlings get the light they need.

“Light is the fuel plants need to grow strong and healthy—if they don’t get enough, they’ll be weak and stretchy looking, and more susceptible to attack from pests and disease,” explains Hancock. “You don’t need a fancy setup—even a LED lamp a foot or so (depending on its strength) above the seedlings can provide the extra boost they love.”

Time Your Planting Right

It’s really easy to get excited when planning your garden for the spring and summer months, but if you don’t tamp down your excitement you could end up planting your seeds too early. You want to make sure they have enough time to sprout but not so long that they have to hang out in their starter pots when they are ready for bigger pots or to go inground.

“Seedlings left too long in their original starter pots will become rootbound and subsequently nutrient-stressed and quick to dry out,” says Miller.

Look at your seed packets when you acquire them to check when you should sow them. The packet will usually tell you the planting time based on your area’s last frost date. 

Provide Good Air Movement

“Most seeds like a warm, humid environment just before they sprout,” explains Hancock. Ensure airflow by placing a small fan near your seedlings that you can turn on during the day and off at night. It will help prevent disease, damp, or rot.