15 Strategies for Successfully Starting Seeds Indoors

1. Purchase seeds from a reputable source.

Don’t let all your hard work be in vein! Get seeds from a reputable seed company or a trusted seed swap or source. This will ensure that you will get good germination rates, receive seeds that were produced from healthy plants, and also grow exactly what you are expecting.

2. Get your timing right.

Timing is also very important. Starting seeds too early can lead to leggy plants, needing to repot seedlings multiple times, or not having enough space and/or lights to accommodate the small nursery that you have created. There are a variety of planting calculators online that will help you calculate the best time to start your seeds (like this Spring Seed Starting Calculator from Johnny’s Selected Seeds). If you have a greenhouse or cold frame, you can start your seeds a few weeks earlier since they will be protected.

3. Determine if you need extra heat.

Most of the time, a heat mat isn’t necessary if you are starting seeds inside of your house, but it can help speed up the germination process. If you are starting your seeds in a cold basement or garage, a heat mat can definitely be beneficial. Click here to get my Vegetable Quick Fact Sheet which lists the minimum, maximum, and optimal germination temperatures for all your favorite veggies.

4. Sturdy (and clean) seed starting trays and pots are a must.

Between watering, rotating, and eventually hardening off, you will move your seed trays around often. Make your life a lot easier by using high-quality and sturdy trays that won’t bend or break when carried (like these trays from Bootstrap Farmer). The last thing you want to do is drop all your starts! I prefer to use 50-cell seedling inserts that fit into 1020 trays with holes. You can also get trays without holes or this nice set that includes either two or ten of each of the inserts, trays, and humidity domes. It is also important to use clean trays and pots that do not have any old dirt residue that could potentially cause problems that you do not want.

5. Use a high-quality seed starting soil mix.

It is incredibly important to use a good seed starting mix when you are growing from seed. I always use an organic potting soil (specifically Espoma Organic Seed Starter Premium Potting Mix), but you can also make your own mix. Many mixes will use homemade compost, but I have never had good results bringing in soil or compost from outside as it is not sterile and most likely contains some unwanted pests. You can make your own seed starting mix using 6 parts peat moss and 1 part fine vermiculite. For a peat-free option, use 6 parts coco coir and 1 part fine vermiculite.

6. Moisten soil before filling the seed trays or pots.

Since the seed starting mix is usually very dry to start with, I find it much easier to moisten it in a large bowl or bucket first. This ensures that the soil is evenly moist and doesn’t get washed away when trying to water the tray. This method has always ensured that the soil is thoroughly moist but not too wet.

7. Label accordingly, and take notes.

Keeping good records of seed starting, transplant, fertilization, and expected harvest dates can be very helpful to come back to throughout the year. You can keep your notes in your own notebook or use my free garden planner and journal. Please, don’t make the same mistakes that I have made and find yourself searching through your phone’s camera roll to find a key date! Also, be sure to use ink or a labeling system that will not wear off when watering.

8. Plant seeds at a depth that is about twice their width.

Most seed packets should have detailed information as to the required depth for proper germination, but this general rule of thumb can be helpful for visualizing what ½ of an inch looks like. Usually, burying the seed too deep is worse than not covering it enough.

9. Maintain humidity and moisture, but don’t overwater.

This can sometimes be one of the bigger challenges of starting seeds indoors in the winter when your heat is most likely on blast and the humidity levels are low. Using humidity domes can be a huge help for germinating seeds and keeping the just sprouted seedlings from drying out. I prefer to use a spray bottle to water my seedlings for the first month or so. Once the seedlings grow several sets of true leaves and establish a nice root system, I switch to bottom watering. As the plants mature, I like to keep their leaves as dry as possible to prevent disease.

10. Pay attention to seed germination times.

Don’t give up on your plants too early. Some seeds like peppers and tomatoes should germinate within a week or so, and others like thyme can take 14-28 days. If it is chilly and outside of their optimal germination temperatures, it might take a bit longer than what the seed packet indicates. My handy vegetable guide lists the minimum, maximum, and optimal germination temperatures for all your favorite veggies.

11. Provide adequate light.

More than likely, you will need to use some sort of additional light source to grow healthy seedlings that aren’t leggy. There are so many different types of lights and options that I could dedicate an entire blog to the subject. In the meantime, Epic Gardening has a great article that goes over this subject in detail. I prefer to use LED lights that don’t cost a fortune. I use these LED grow lights that are about $40 each from Amazon. Last year, I got away with using only one grow light per seedling tray. However, this year, I am experimenting with using two hung above each tray.

12. Rotate seed trays or pots every few days.

There is usually some light differences caused by the angle of the light or additional sunlight coming in through your windows. Rotating your trays every other day ensures seedlings grow straight and evenly. If you notice an area on the tray that gets more light, it will most likely get dried out quicker, too (so keep an eye out).

13. Use a fan to increase airflow.

This is an easy method that will help prevent pests and diseases. Using a small fan for at least a couple hours a day also helps make your seedlings stronger and increases their chances of survival in the great outdoors.

14. Remember to fertilize your seedlings.

Most organic or DIY seed starting mixes don’t contain many nutrients (if any at all). Be sure to fertilize your seedlings shortly after they emerge, but be careful not to overfertilize. Dilute liquid fertilizers to half-strength for the first 1-2 feedings to avoid overfertilizing your seedlings which can actually stunt their growth and make them vulnerable to pests and disease. You can also use slow-release fertilizers such as Sustain 4-6-4 Organic Flower & Vegetable Fertilizer which is what I like to use on my seedlings and container plants.

15. Always harden off your seedlings before transplanting.

Last but certainly not least, be sure to acclimate your seedlings to the outdoors before sending them on their way. This process is called “hardening off”, and it usually takes at least a week (more than likely two) to accomplish successfully. For the first couple days, you don’t even want to put your plants in the direct sunlight. Put them in a shady area where they are sheltered but still exposed to the outdoor air for an hour or two. On the third day, start bringing them out into the sun for maybe an hour (but keep an eye on them). Gradually start to increase the amount of time they are in the sun very slowly. Eventually, they will be strong enough to withstand the sun all day, but you may still need to bring them indoors at night depending on the crop and outdoor temperatures. Don’t rush this process! You don’t want all of your hard work to go to waste. When your seedlings are ready to be transplanted, choose a cloudy day with rain in the forecast. That is my favorite time to transplant!

Please note: I have included links to products on this page for your convenience. Some of them are affiliate links (Amazon, Vego Garden, Subpod, and Botanical Interests). This means that, at zero cost to you, I will earn a small commission from purchases made through those links which helps me keep this site up and running. Thank you!

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