How To Start Seeds Indoors

We can all agree that vegetables, herbs, and fruits are becoming very expensive; instead of buying fresh produce, why not grow seedlings indoors yourself? Starting seeds indoors is inexpensive, and you can get many plants instead of paying for one plant.

Hence, you have many choices as a gardener to grow what you enjoy in your home garden. You can start newly planted seeds indoors and transplant seedlings outdoors when the time is right.

But how can you start your seeds indoors? Well, we are here to help you with this process, no matter if you want to start with vegetable seeds, herbs, or other flower plants.

The truth is the method used remains the same with some slight differences.

When To Start Seeds Indoors

seeding indoors

When starting seeds indoors, you still need to start them at the correct time. Why? When starting seeds too early, your plants grow out of the pots before you can transplant them.

Still, when you plant seeds too late, they will not reach maturity in time before the growing season ends. So, where do you start? You start right here!

Starting Seeds Indoors Comes Down to Your Selection

The important thing is to buy good quality seeds from a reputable dealer. We recommend looking at the seed packets we have available in the shop. You know you are getting plants true to the cultivar or variety name with a quality seed.

Neither will the seeds contain contaminants like weed seeds, soil particles, insect castings, or even plant pulp. Then research the varieties you want to grow in the existing growing condition.

So, check the color, growth habits, to size, and you may even find some resistant to diseases. Also, choose seeds that can grow in your area to ensure it reaches maturity before the frost, can survive the heat, or tolerate the current growing conditions.

Only purchase enough seed packets to use in that current season. You can store a seed packet from one year to another, but it can lessen the germination as it declines with age and not storing correctly.

The important thing is to store your excess seeds in a dry, cool place in paper bags or containers with low humidity. An excellent location is the crisper drawer of your refrigerator. Some seeds are found in a treated form with a fungicide coating to increase survival.

Others come in a pelleted form with a clay coating, as it becomes easier when you sow seeds with the layer. You also find legume seeds with nitrogen-fixing bacteria helping plants to draw nitrogen from the air to reach the roots.

Then you have hybrid seeds that are costly and also treated.

Read Seed Packet Instructions

seeds in a packet @flickr

With your seed packet, you get a lot of information:

  • First, look at the year of the production as you will find it printed or stamped on the package.

  • Look if the seeds you buy are packed for the current season.

  • Furthermore, you also find information on how far apart you need to space seedlings when starting seeds indoors.

  • Another notable thing is the depth of how to sow seeds and the days to germination.

  • You will find information on how to thin out your seedlings. You will also find the planting dates and if needed, plant before the last frost date.

The Importance of Germination When Starting Seeds Indoors

onion seeds germination

The germination process is how long the embryo will take to emerge, and it all starts with the imbibition or the absorption of water. Hence, there are four important environmental factors to consider.


seed germination in petri dish

Seeds germinate with water as the first step to germination. If seeds indoors do not receive, the water remains dormant. Still, too much water results in rot, while too little results in the embryos dying.

Hence, seeds need consistent moisture when you start them indoors or outside. You can mist seeds indoors with a hand-held spray bottle or a mist nozzle. You can also cover your planted seeds with vermiculite or a thin layer of peat moss.

Or invest in a seed starting mix if you do not want to create potting soil yourself. Then, keep the seeds indoors in high humidity by covering the seed trays with a plastic bag to remove them once they germinate.

So keep the soil moist but not soggy to improve the germination change.


seed germination under bright light

Depending on the seeds, most seeds need light to germinate, while others need darkness. We recommend looking at the seed packet for the information. For light, sow seeds on a soil surface and cover them lightly with delicate moss or vermiculite for darkness.

Air Circulation

seed germination

Live seeds respire, and they release carbon dioxide to consume oxygen. As the seedlings grow, more respiration occurs, and they need more oxygen. Your seed starting mix must drain well and have air circulation, or it might result in death ☠.


seed germination temperature

Temperature is also critical as it will determine how fast seeds grow. You may find that some seeds indoors need a specific temperature to germinate. A rule of thumb is to provide between 65°F and 75°F.

You can monitor the soil using a thermometer. If you need to increase the temperature, use moisture-proof heat mats or grow lights.


When seeds are started indoors, the material is as essential as water, temperature, and air circulation to light.



We recommend a sterile seed starting mix without any fertilizer in it. These are better than ordinary potting soil as it has no weed seeds or disease organisms. Another recommendation is to avoid heavy garden soil that holds water for other tiny seeds.

The potting media will be OK with an even texture. It helps maintain contact with the seeds. You can mix a soilless mix like vermiculite, perlite, sand, and peat. Another great soil medium is to:

  1. Four quarts of shredded sphagnum peat moss

  2. Four quarts of fine vermiculiteite

  3. One tablespoon of superphosphate

  4. Two tablespoons of ground limestone

When mixed, you can wet it well, leave it to drain, and only plant seeds in it in five to six days. Doing this allows the lime to blend with the other potting mix. You can grow most plants in it as the seedling growth is excellent.


seeds container

You can use any form of container to start most seed packets indoors. The important thing is it needs to drain well to prevent rot. It would be best if you also sanitized the pot beforehand. Alternatively, you can find peat pots, seed trays, to other seed-starting containers at your local garden center or here with us.

We recommend sanitizing whatever you plan to use except for the peat pots. Make a solution of nine parts water with one part chlorine bleach to rinse the containers.



From air to soil temperatures, soil moisture is essential when you sow indoors or outside. So, choose a warm location with bright light and ample air circulation.

Seeding Guide For Most Seeds

Whether you grow tomato seeds, annual flowers, or other seed varieties indoors, you can do it directly or transplanted. The majority of seeds you plant at a depth twice their diameter. While small seeds press into the potting soil and are barely covered.

You can start seeds earlier covered with a plastic bag, and once seedlings start, you can remove them and use grow lights. But this is an additional method, as you can still sow seeds indoors in a warm spot with enough light.

Here, we will discuss both techniques and what seeds grow well in these conditions.

Direct Seeding

direct seeding

Not all seeds respond well indoors for transplanting. For example, beans cannot benefit from transplanting. For instance, large plant seeds like pumpkin and corn and root crops like carrots to beets are best done directly in the ground.

You can grow the seeds indoors in a container or in a spot where you need not transplant them. Yet, following the seed packet’s directions for the recommended planting time and depth is best.

Still, small varieties like tomato seeds can be challenging, and it helps to prepare a bed and closely pay attention to the germination to the initial growth. Some seeds to grow directly are carrots, oak, sunflower, beet corn, green beans, and dill.



Following your planting schedule, some seeds can be germinated in a seed tray or container to transplant. Then, you can start indoors, and once seedlings grow true leaves, we recommend using a pencil or dibble tool to help probe the roots.

Then, lift it gently and use your tool to create another hole in the new container or a location. Set your seedlings at the same depth; they grew in the pot. Never grab the stems, as it will damage the roots.

The best time is to transplant your seed indoors into young seedlings according to your area’s average last frost date. Once transplanted, water the young plants well and check the soil moisture daily.

Then, feed your plants a soluble fertilizer after a week, allowing them to establish and become more root-bound. You can then feed them at two-week intervals.

Plant seeds to start indoors:

  • Brocollie

  • Brussel Sprouts

  • Cabbage

  • Cauliflower

  • Lettuce

  • Peppers

  • Tomato plants

  • Pansy

  • Alyssum

When To Transplant Seeds Outdoors

seeds germination

The best time to transplant young plants outdoors is after the final frost date; it all comes down to timing.


seeds germination outdoors

When you start seeds indoors as transplants, it is all about timing. First, you want your seedlings to be ready when the soil temperature rises, and it is warmer outdoors. Still, when started indoors too early, your plants might not be prepared for the outdoor world.

When you time things correctly, your warm-season plants like squash, tomatoes, and marigolds will be ready to plant outside in spring by the last frost date. During cool weather, crops like cabbage, pansies, and broccoli must be planted in the fall garden before the first frost.

The best is to sow your seeds indoors a few weeks or at least eight weeks before the transplant. For instance, if your average last frost date is April 15, you must plant your tomatoes indoors in late February to early March.

For the best info, refer to a planting date on a chart.

Thinning Seedlings

Thinning Seedlings

You will sow your seeds indoors and use two or more seeds as gardeners. But for precaution, you plant more seeds than what you desire. This is especially true with tiny seeds like carrots.

Regardless if they end up in a small space, you need to thin them out to provide them space to grow and not become root-bound. We recommend following the spacing information available on the packets.

Hardening Off

hardening off

When you grow your plants indoors from seed in high humidity and sheltered from the elements outside, they need to harden off. So, moving your plants into a shady location is best.

Then, gradually increase the sunlight over a couple of days. We recommend moving your seedlings outside for a few hours on a cloudy day. Then, repeat the process and length daily until they acclimate to full sun.

Then, you can transplant them into the landscape by doing it gradually.

Final Thought

As you can see, following a planting schedule and the planting dates, you can sow your seed inside. The important thing is to be seed-savvy and make a list of what you want to grow. So plant the best seeds indoors and prepare yourself for some losses.

Get a few seeds a couple of weeks earlier, as it will not be such a huge loss when you lose some of the seedlings. Also, if you store your seeds, keep the packet over the pot when throwing it back. It prevents seeds from being wasted.

So do some intelligent planning and keep checking in as we plan a feast of articles on planting and growing seeds.

Whether you want to buy, sell or simply reach out to other plant enthusiasts, Plantly is the right place to be!

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