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How to Start Seeds Indoors: A Complete Guide for Beginners

Introduction: What is Indoor Seed Starting and Why Should You Do It?

Indoor seed starting is a great way to get a jumpstart on the growing season. It allows you to start your garden from the comfort of your own home, and it's an easy and affordable way to get started with gardening. With indoor seed starting, you can control the environment for your plants and give them the best possible chance for success. You can also save money by buying seeds instead of plants, and you can choose from a wide variety of vegetables, flowers, herbs, and other plants that are suited to indoor and outdoor growing conditions. Whether you're new to gardening or an experienced gardener looking for something new to try, indoor seed starting is a great option.

Steps to Get Started with Indoor Seed Starting

To begin, it is important to know when to start your seeds indoors. Depending on what type of plant you are growing, this time frame will vary. You will also need to consider what kind of seed germination supplies are needed for successful planting and growth. Finally, there are specific steps that should be taken when starting vegetable seeds indoors in order to give them the best chance at success. With these tips in mind, you can get started on your indoor seed-starting journey!

Steps to Get Started with Indoor Seed Starting

Not all seeds are good for starting inside as some plants do not transplant well. Some seeds start so quickly, it's not feasible to start inside (e.g. pumpkin). Before starting, make a list of plants you will have, then identify which ones should be started inside. Cherry tomatoes are a great option to start inside so you can get more produce sooner. Keep in mind your region’s frost dates when you make your seed planning.

Before Planting the Seeds

Depending on the seed’s requirements, put the seeds into water and let them sit for a while (hard seeds like peas should be soaked in water for around 24 hours). And then pull the seeds out and plant 4 into each cup. Place wooden labels after putting the seed.

Check out our Seed Library to see which seeds require soaking before sowing.

What are the Best Soil and Containers for Growing Seeds Indoors?

To get the best results, you need to use the right soil and containers for your seedlings. The soil should be lightweight and provide adequate drainage, while the containers should be large enough to give the seedlings plenty of room to grow. Knowing which type of soil and container will best suit your needs can help ensure a successful indoor garden.

Do not plant and then transplant to bigger pots 2-3 times. Root mass is important. In order to avoid distressing the plant roots, start with a size for the roots of the final form of the plant.

In order to avoid moving the seedling from its initial pot during transplantation, you can choose biodegradable pots so you can directly sow it outside with the pot when the time comes. This is a good choice for slow-growing plants.

How big is the root going to be?

Rule of Thumb: Similar in size to the upper body of the plant.

Do not let the plant get too big before planting outside. Roots need to expand to feed the plant. For example, if you keep a pepper plant inside for too long and then transplant them outside, leaves might fall off.

How to put drainage holes in seedling pot
How to put drainage holes in seedling pot

Tip: If you plan to grow too many seedlings at the same time, one of the easiest solutions is to contain all of the seedlings in one big container and pour water once on the bottom. This way you can leave the seedlings making sure they will always have enough water.

This method requires you to create small drainage holes into the bottom edges all around the plastic pots, not just the bottom (soil would block the holes from the bottom and roots would not access the water.

Put the cups into a deep plastic container and fill the container with water as shown. Cups should not float on the water (that means there is too much air inside the soil).

Tip: Put the water into the soil inside the cups 1 day before planting the seeds, so that the water evens out inside the soil. Let the water sit in the soil and work the way down inside the cups.

The temperature at the root zone will be close to the temperature of the water. Keep it above 10-15 degrees Celsius at all times. Use a thermometer and look out for the water temperature.

Planting the Seeds

If you plant the seeds too deep, they would die before even reaching the light. If you plant it too shallow, the seed can’t access water and dirt.

Rule of Thumb: Widest point of the seed is the distance to plant in the dirt. If you are not sure of the depth, less is better.

Do not compact/compress the dirt as it traps the seed. Leave it loose.


You can plant multiple seeds and keep the strongest seedling coming out - or transplant others into separate cups carefully. Do not wait too long for transplantation but also give time for it to grow out of the surface.

Do plant it ahead of time so that if it does not germinate, plant it once more.

Don’t plant the seeds close if you are planting multiple seeds.

Tips on Watering, Lighting, and Temperature

It can be difficult to know how to properly light and water your seedlings. Here we will provide tips on setting up the right grow light setup for your seedlings, how to water them properly, and what temperature you should be growing them at.

Watering Tips

Starting seeds indoors is a great way to get a jump start on your garden and ensure the healthiest plants possible. However, there are common mistakes that can be made when starting seeds indoors that can lead to unhealthy plants and poor yields. One of the most common mistakes is over-watering your plants from the beginning of the life cycle. Over-watering can cause root rot, which will stunt your plant’s growth or even kill it before it has a chance to thrive in its new environment. To avoid this mistake, make sure you understand how much water each type of seed needs and then stick to a consistent watering schedule.

  1. Always keep the leaves dry to avoid diseases

  2. Excess water causes a lack of oxygen.

  3. Distilled or softened water is not recommended

  4. Too hot or too cold water is not recommended

  5. Break up any large clumps before watering the dirt.

Lighting Tips

Seeds generally do not need light before sprouting. As soon as the seeds pop out, they need light quickly within the first few hours, otherwise, they will become tall. Lack of sunlight causes tall but weak plants. Here are some other lighting tips:

  1. The color temperature of the light: Red lights are good for flowering and fruits. 4000 - 7000 Kelvin is ideal.

  2. South-facing windows give good and unobstructed light

  3. Use a light meter

  4. If you are using LED lights, use chains on all sides to increase-decrease the light distance from the plants. Keep the light close to the pot during initial germination and then pull up.

  5. If there are different heights of plants, keep the light slantwise.


Seeds won’t even start if the room temperature is too cold. In general, 30 degrees Celsius is ideal for sprouting vegetable plants.

Plant temperature is more important for the roots than the tops of plants.

Tip: Lighting also generates heat, and dark-colored plastic pots help to convert the light into heat around that area.

Lighting also helps to hold in humidity which young seedlings will appreciate.

Tip: You can also use an electric heater and temperature monitor, though gas heaters are not recommended as the gas may harm the plants.


If you have a long period inside with the plants you might need fertilizer though it’s not common. If the growth has slowed and the leaves turn yellow and weak, you can try small amounts of fertilizer.

Nitrogen is important at this stage. But do not encourage high Nitrogen growth in plants as it may impact the long-term health of plants. Don't give more Nitrogen it needs.

Hardening Off Before Transplantation

Before transplantation, prepare your plants for outdoor conditions.

You can slowly introduce the seedlings to the new environment, for a couple of hours every day. Since the humidity will be lower outside they might need more water than they needed inside. Slowly lower the water amount before taking them outside.

Stop any fertilizer use completely during the transition. A lack of fertilizer will not hurt the plant. Root starters might give an extra boost for root growth (Vitamin B1 - Chelated Iron, Manganese, and Zinc).

If the plant had a shock but there are new green leaves coming, it will be OK. Some plants are extremely sensitive to root disturbance. Some roots are not even visible so you might destroy them during transplantation. Make sure to transplant it into wet soil.

Tip: Whenever the last frost date is, add a couple of more weeks to avoid unexpected weather changes.

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