How to Plant Seeds in a Basic Seed Tray

Planting seeds is a great way to start plants indoors for your garden. Using seed trays helps your plants grow easily and with minimal effort. By getting your seeds ready for the spring, you’ll have seedlings ready to go outside in no time!

Part 1

Part 1 of 3:

Creating a Grow Area

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1
Plan to start planting seeds between 6-12 weeks before the last frost date. Actual growing time for seeds will depend on what plants you’ve decided to grow. Planning around the last frost date for your area will help you determine when to start germinating the seeds.^{[1]XResearch source}
- Read the packaging on the seeds you are planting to see if additional steps, such as soaking or chilling, need to be taken before they are planted.
- Check the Old Farmer’s Almanac for growing dates specific for your region.
2
Purchase a cell tray with drainage holes for an easy option. Using a cell tray allows the seeds to grow without interfering with one another. Opt for cell trays that have drainage holes at the bottom if you can. They can be purchased at any gardening store.^{[2]XResearch source}
- If your cell trays do not have drainage holes at the bottom, use a knife to poke holes in the bottom of each cell.
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This biodegradable option has perfect sized cells for planting and you may already have one in your home. After you’ve used all the eggs in a carton, poke a few holes at the bottom of each cell so the soil has good drainage.^{[3]XResearch source}
4
Place the cell tray inside a large, flat plastic tray. The flat tray will make it easier to transport and water your seedlings. Since you’ll want your seeds to establish roots, you’ll be watering in the flat tray to promote downward growth. The plastic trays can be purchased at any gardening store.^{[4]XResearch source}
- A baking pan is an alternative that you may already have in your home.^{[5]XResearch source}
5
Fill each cell to the top with a seed starting mix. Seed starting mix is a sterile alternative to potting soil that will help promote germination for your seeds and can be purchased in stores or online. It’s okay if you overfill since the mix will set further once it is wet.^{[6]XResearch source}
- Potting soil can be used, but it may be more coarse and the seeds may not grow as well as they would in a fine seed mix.^{[7]XTrustworthy SourceMichigan State University ExtensionExtension program of Michigan State University focused on community outreach, education, and engagementGo to source}
Push your finger into the soil to your first knuckle and make sure it is damp. Excess water should drain through into the tray underneath your cells.^{[8]XResearch source}

Part 2

Part 2 of 3:

Sowing the Seeds

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1
Submerge old seeds for 15 minutes in water to see if they are still viable. If you have old seed packets you are hoping to plant, you’ll want to test if the seeds are still good to grow. Some seeds can last for years, but others will have a shorter shelf life. If any seeds float, then they will most likely not grow. If the seeds sink, they should still be good to plant.^{[9]XResearch source}
- Alternatively, you can run a germination test by wrapping at least 10 seeds in a damp paper towel. Keep the paper towel in a resealable plastic bag in a warm place for 10 days. Check the seeds to see if they’ve germinated or sprouted. If 5 or more sprout, the rest of the seeds should be viable.
2
Poke a ¹⁄₄ inch (6.4 mm) deep hole in each cell with your finger. The measurement doesn’t have to be precise, so half the length of a fingernail is a good estimate. Be gentle as you press so you don’t pack the soil firm.^{[10]XResearch source}
- Some seeds may need to be set shallower or deeper, so follow the instructions on the seed packages for each plant.
3
Plant at least 2 seeds in each hole. This helps make sure at least one of the seeds will germinate in each cell. If both of the seeds start to grow, you can always cut back or remove the weakest looking plant.^{[11]XResearch source}
- Plant 4 seeds if they are small. This gives more chances for them to grow.
- If you’re working with small seeds, pour the seeds into the crease of a folded piece of paper and use a pencil to push the seeds into the hole.
This makes sure the seed has complete contact with the starter mix. Be gentle as you press down. You do not want to push the seed in deeper; you just want to pack the soil closer.^{[12]XResearch source}
5
Label the seeds if you plant more than one kind. Make garden labels for your plants, listing what is growing in the cells as well as the date you planted them. Stick the labels at the end of each row.^{[13]XResearch source}
- Using toothpicks and masking tape is an easy alternative for garden labels that you can make at home.

Part 3

Part 3 of 3:

Caring for Your Seedlings

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1
Cover the tray with plastic wrap. Plastic wrap will help keep the moisture in the tray for longer and create a humid environment that promotes germination. Leave small openings on the sides of the tray so air can still circulate to your seeds.^{[14]XResearch source}
- You can also purchase a humidity dome from a gardening store for the same effect. If the dome has an air vent, keep it open for air flow.
2
Fill the flat tray with ¹⁄₂ inch (13 mm) of distilled water. The cells will soak up water from the tray so you do not have to water your seeds from the top. Check the levels of the water in the tray daily.^{[15]XResearch source}
- Fill the tray back to ¹⁄₂ inch (13 mm) of water when levels are below ¹⁄₈ inch (3.2 mm) deep.
- If you overfill the tray, the roots of your seedling may become waterlogged and develop rot.
3
Store the tray in a warm area. Sunlight is not essential for seeds to grow, but it will not hurt them either. Keep the tray in the warmest area of your home. The soil temperature should stay above 65 °F (18 °C) for most plants to successfully germinate.
- Soil temperature can be measured with a soil thermometer placed at the same depth as the seeds.
4
Move the tray to a sunlit area once seedlings sprout and uncover them. Once you see sprouts in your cells, move your tray to a windowsill or an area with about 6 hours of indirect sunlight. Remove the plastic wrap or humidity cover so your seedlings can get full exposure to the light.
- Turn your tray 180° every other day so your seedlings do not grow crooked.
- You can also keep seedlings under grow lamps so the plants will grow evenly.

Expert Q&A

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Can you germinate seeds in soil?
Maggie Moran
Home & Garden Specialist
Maggie Moran is a Professional Gardener in Pennsylvania.
Maggie Moran
Home & Garden Specialist
Expert Answer
If you are growing the plants in water, like a hydroponic garden, most seeds end up living in the soil. There are some that do thrive in sand as well.
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How long do seeds need to dry before planting?
Maggie Moran
Home & Garden Specialist
Maggie Moran is a Professional Gardener in Pennsylvania.
Maggie Moran
Home & Garden Specialist
Expert Answer
If you want to grow plants from fresh seeds, it’s a good idea to dry the seeds for 1-2 weeks if you are planning to store them. If you are planting them right away, this is not required.
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Can you start seeds in egg cartons?
Maggie Moran
Home & Garden Specialist
Maggie Moran is a Professional Gardener in Pennsylvania.
Maggie Moran
Home & Garden Specialist
Expert Answer
Yes, you absolutely can! Each egg cup makes a perfect single seed starting pot.
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