How To Start Seeds Indoors Without a Grow Light

Growing seeds indoors gives you a headstart on the growing season. Many growers believe that you need an expensive array of artificial grow lights to compensate for the lack of sunlight indoors. Fortunately, you do not need grow lights to start seeds indoors.

You can start seeds indoors without a grow light by keeping them in the brightest spot in your house and providing adequate warmth and moisture. Use viable seeds, pre-soak them, and sow them in a light and airy seed starting mix. Harden off the seedlings before moving them outside.

Seeds sprout without adequate light if you create favorable conditions for germination and provide the right growing medium and proper warmth and moisture. I will ewaxplain in this article how to create the right conditions for sprouting seeds and describe how to nurture seedlings and give them the best chance of surviving outdoors.wa

1. Choose the Right Seeds to Grow

Some plants have tender roots that get damaged when the seedlings are transplanted. The seeds of these plants, such as carrots and beets, should ideally be directly sowed in the ground

Wait till the last frost date in your area before directly sowing seeds. 

You should also buy seeds from reputable suppliers and check the germination rate on the package before buying. 

You may have leftover seeds from last season. Some of them may still be viable, but some will not germinate. The quickest and easiest way to determine if a seed is viable is using the paper towel method. Here’s what you do:

  1. Dampen a paper towel, filter paper, or newspaper.
  2. Scatter some seeds on the towel.
  3. Cover the seeds with another damp paper towel
  4. Place the towels with the seeds inside a clear, zip-close bag. 
  5. Seal the bag.
  6. Keep these seeds in a warm location away from direct sunlight. 
  7. You will observe if any seed germinates, which should be within 5-7 days.

Use tweezers to hold the seed body or a leaf and transplant the sprouted seed to a container where it will continue to grow. Poke a hole in the potting soil, gently place the seed inside, and cover it with soil. The first set of leaves, if there are any, should be above the ground.

2. Prepare the Seed Starting Mix

The ideal seed starting mix is light, airy, and fluffy, so the seed can push through the soil, and the roots can expand unhindered. The mix should hold on to moisture while promoting excellent drainage. Equally importantly, the seed starting mix should not compact when packed in a tiny seed starting module. 

You can buy seed starting mix from the store. Some of these mixes contain chemicals that manufacturers claim speed up germination. 

However, a seed contains inside it the energy and the food it needs to germinate. It does not make sense to pay more for ingredients that the seed doesn’t need.

Besides, making your seed starting mix at home is cost-effective if you are a prolific grower. 

Ideally, a seed starting mix should not contain soil. Your usual garden soil is too heavy for delicate roots to grow. Dense garden soil also tends to compact and may contain weed seeds and soil-borne pathogens that can cause damping off disease in the seedlings.

You only need the following three ingredients to make your own organic seed starting mix:

  • Perlite: Perlite promotes drainage and makes the mix light and airy.
  • Vermiculite: Vermiculite has excellent water-retention properties. It absorbs excess moisture from the mix and prevents root rot.
  • Sphagnum Peat Moss: There is sphagnum peat moss, and there is sphagnum moss that is used to line flower pots. Sphagnum peat moss is finer than sphagnum moss and can hold more moisture. Read the label on the bag carefully when buying. 

These ingredients are readily available in all garden stores or can be ordered online. 

The extraction of sphagnum peat moss from bogs releases carbon into the air, contributing to global warming. Coco coir is an environmentally-sustainable alternative to sphagnum peat moss.

Mix one part of each ingredient to make your seed starting mix.

You can also sow seeds in store-bought potting mix or potting soil that contains ingredients like topsoil or dirt, perlite, vermiculite, bark, manure, peat moss, humus, and fertilizers. However, seeds do not need most of these ingredients to germinate. Besides, potting mix does not drain as well as seed starting mix does. 

3. Pre-Soak Seeds To Speed Up Germination

Soaking the seeds of some vegetables and fruits in water before sowing speeds up the germination process. This is true for seeds with hard shells. This method is called pre-soaking

Seeds need moisture to germinate. The outer shell or the seed coat swells when it comes in contact with moisture and ruptures to free the embryo inside. This embryo develops into a plant. 

Seeds with hard coats take more time to germinate than those with soft coats. It takes longer for the moisture to permeate a thick shell. 

Pre-soaking seeds softens the thick coats and speeds up the sprouting process when you sow the seeds.

The thicker the seed coat, the more the seed benefits from pre-soaking. It is a good idea to pre-soak seeds of fava beans, peas, corn, beets, okra, cucumbers, squash, and nasturtiums. 

Soak the seeds in a bowl of warm water. Soak thick seeds like those of peas for about 8-10 hours. 

The seeds of snap beans are thinner. You should soak them for no longer than four hours. Else, they will rot. 

If you are not sure how long you should soak other seeds, go by this rule: Soak the seeds and check them after every few hours. When the seed coats plump up, remove them from the water and sow them.

Leaving the wet seeds lying around for too long will cause them to rot. 

4. Sow the Seeds

You can sow the seeds in seedling trays, peat pots, coco coir pots, egg cartons, or yogurt cups. Sow them about six weeks before the last frost date in your area. 

Here are the steps of sowing seeds indoors:

  1. Moisten the seed starting mix. Watering after you have sown the seeds may displace them. Pour the soil mix into a large container, pour water over it, and mix with your hands or a trowel. Peat-based seed starting mixes absorb water slowly, so you may have to add more water. Add water till the mix is uniformly moist and attains the consistency of damp sand.
  2. Fill the container where you will sow the seeds with the moist mix. 
  3. Poke a hole in the mix with your finger or a pencil. The seed packet will carry instructions on how deep to sow the seeds. If you don’t have this information, the general rule is to sow the seeds twice or thrice as deep as their width. You don’t have to bury those seeds that need light to germinate.
  4. Sprinkle the seeds in the hole. Place one seed per hole if they are large, such as those of cucumber, squash, or corn. If the seeds are tiny, such as those of basil or mustard, you can sow 2-4 seeds in each hole and thin out the seedlings later. Sprinkle those seeds that need light to germinate on the surface of the seed starting mix.
  5. Cover the hole with the seed starting mix. Gently tap down the mix in the hole to ensure it makes good contact with the seeds. Lightly press down the seeds you had sprinkled on the surface of the mix to help them settle in. 

5. Label the Seeds

Use popsicle sticks or plant markers to label the seeds. Recording the names of the seeds and dates when they were sown helps you schedule their transplanting outdoors. 

Many brassica seedlings look similar till the true leaves appear. Labeling helps you identify what seeds you have sown. 

Labeling also lets you keep track of the germination rates of the seeds. This information comes in handy when you sow new varieties and want to keep track of their performance.

Pop the labels into the soil at the edge of the seed starting tray or container.

6. Water the Seeds

Keep the seed starting mix moist after sowing, but do not overwater. Soggy conditions can attract fungus and cause damping off disease in the seedlings. 

Keep the following tips in mind when watering:

  • Water from the bottom to prevent overwatering. Place a tray beneath the container where you have sown the seeds, and add water gradually for 10-30 minutes. The seedlings will absorb the water through the drainage holes. Remove the bottom tray when the top of the seed starting mix feels damp.
  • Use a spray or squirt bottle. Do not use a hose to direct a jet of water at the soil. The force of the water can displace the seeds or damage the fragile roots of the seedlings. Use a spray or squirt bottle that dispenses a fine mist of water.
  • Create a humid microclimate for the seeds. Cover the seed tray with a transparent plastic sheet to trap moisture inside and moisten the soil. You can poke a few holes in the plastic sheet to let excess moisture and heat escape. You can also use a glass or plastic humidity dome fitted with vents or a plastic container with a lid.  
  • Check soil moisture every day. Do not let the seed starting mix dry out completely. Also, watch out for soggy conditions. Act immediately to dry out the soil; my article here has some tips for you on what to do when indoor plant soil stays wet: What to Do When Indoor Plant Soil Stays Wet
  • Use a specialized self-watering seed-sowing setup.

7. Keep the Seed Starting Mix Warm

Extreme heat dehydrates the soil and can prevent seeds from germinating. On the other hand, cold soil slows down germination or stops it in the case of seeds of warm-season crops. 

The ideal soil temperature for germinating warm- and cool-season crops is 75°F (24°C). This temperature is neither too warm nor too cold.

It can be challenging to keep the seed starting mix warm indoors during winter. Here are some ways in which you can keep the seed starting mix warm:

  • Keep the seeds on a south-facing window sill. Here they will receive plenty of sunlight for most of the day. Open the curtains during the day. However, move the seeds to a warmer location at night if cold air tends to enter the house through this window at night.
  • Cover the seed tray with clear plastic. The plastic will trap heat and keep the soil warm, especially if you have placed the seeds in a spot with plenty of sunlight.
  • Use a seedling heat mat. A seedling heat mat provides heat from below. The heat moves up the mix to warm the seeds. Keep the heat mat plugged on till the seeds germinate. Some heat mats are large enough to accommodate four standard-sized seed trays, while others have thermostats that let you control the temperature.
  • Cover the seed container with a humidity dome. Besides creating a humid microclimate for the seeds, a humidity dome keeps the heat inside. These domes can be made of glass or plastic. Some domes have vents; you can keep them closed to trap the heat.
  • Make an enclosed box and insulate it. You can line a wooden crate or a cardboard box with flat pieces of Styrofoam, aluminum foil, or a blanket to insulate it. Ensure that you make a cover for the box using Styrofoam, clear plastic, or aluminum to trap heat inside.
  • Generate heat inside an enclosed box. An insulated box merely traps heat inside; it does not generate warmth. You can create heat and speed up germination by placing a hot water bottle or disposable hand warmers inside the box. 
  • Water with warm water. Cold water from the tap will cool down the soil. So, let the water sit out for a while and warm up to room temperature before using it to water the soil. 
  • Place the seeds near a heating appliance. You can keep the seeds near a room heater, wood stove, or hot water heater. The heat radiating from these appliances will keep the seeds warm. Ensure that you keep the seed trays on a bench or a table near the appliance and not on top of it.
  • Keep the seed tray on top of the fridge. If you have an old refrigerator, keep the seed tray on top of it. Old refrigerators and freezers that are not very energy-efficient tend to emit quite a lot of heat on the top. 

You wouldn’t want the soil to overheat and dry out the seeds. Ensure that you monitor the temperature if you have kept the seed trays near a heating appliance. Remove the seed trays from the window sill if the sun is too harsh

However, the seeds of some cool-season crops may need a colder environment than what is inside your home. You have to keep these seeds in your basement or root cellar. Move the trays to a warmer and brighter location, such as a south-facing window, when the seedlings emerge.

8. Transplant the Seedlings

The small cells of a seed tray do not provide adequate space for the roots of seedlings to expand. You should transplant the seedlings to larger containers to help them grow. Seedlings become hardy enough to be transplanted after their first few sets of leaves appear.

Keep the following points in mind when transplanting seedlings:

  • Choose the most vigorous seedling to transplant if more than one seed has germinated in a single cell.
  • Remove the seedlings from their cells by gently holding their leaves, NOT the stem.
  • Plant the seedlings in a potting mix.
  • Keep the seedlings in a bright, sunny spot. 
  • Keep the soil moist but not soaking wet.
  • Rotate the container daily to ensure all sides of the seedling receive equal light.
  • Fertilize the seedlings with a diluted solution of all-purpose fertilizer or compost tea.

9. Harden off the Seedlings

If you want to plant the seedlings outside, start by hardening them off. Hardening off seedlings helps them acclimatize to the external environment before they eventually leave the sheltered confines of the indoors. 

Here’s how you should harden off tender seedlings:

  1. Move the seedlings to a sheltered spot in your yard or the porch where they receive diffused sunlight.
  2. Bring them indoors at night to protect them from the cold. 
  3. Follow this routine for about a week.
  4. Move the seedlings to a spot where they receive partial sun.
  5. Bring them indoors at night.
  6. Follow this routine for another week.
  7. Move the seedlings to a site where they receive full sun.
  8. Bring them indoors at night.
  9. Increase the time you keep the seedlings outdoors till they can remain outside all night.

Plant the seedlings in the ground after the last frost date in your area. 


Growing from seed is always more cost-effective than buying plug plants from the garden center. 

However, many growers are unaware that not all seeds need light to germinate, and many others sprout even when they do not receive bright, direct sunlight.

Knowing how to start seeds without a grow light and without using expensive store-bought seed starting mixes lets you grow as many crops as you want, prolong the growing season, and reap more harvests.

You can read this article to understand more about the effect of darkness on seedlings: How Long Should Seedlings Be Left in Darkness?

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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