The Beginner’s No-Fail Guide to Starting Seeds Indoors (2024)

The Beginner’s No-Fail Guide to Starting Seeds Indoors

If you're new to seed starting, this foolproof beginner's guide to starting seeds indoors will take you step by step from seed to harvest, quickly and easily. You don't need any fancy gear or grow lights to get started, and you can even upcycle small containers to put your seeds in. All that's needed is a sunny window, a basic seed-starting mix, and something underneath your pots to catch drips.

Exactly as the title says — this is an easy, no-fail guide to indoor seed starting.

You don’t need to read any gardening books first. You don’t need any fancy equipment. You just need your seeds (these are the best garden seed catalogs that I order from every year) and a few basic supplies to get started.

Whether you have a dedicated vegetable bed in your backyard, or a cluster of containers on your patio, it all starts out the same way. You have to plant your seeds, and germinating seeds inside your home (where you have the most control) is the best way to do so, especially for seeds that are hard to start.

Starting seeds indoors is ideal if you want to get a head start on the season, or if the weather is still too hot or too cold to put anything in the ground.

Related: Find First and Last Frost Dates Accurately with This Custom Planting Calendar

This simple step-by-step tutorial will take you from seed to seedling with a minimum of fuss. Just the stuff you need to know, and none that you don’t. (But if you’re the really-need-to-know type, I’ve added footnotes at the end to explain why you’re doing what you’re doing.)

Disclosure: All products on this page are independently selected. If you buy from one of my links, I may earn a commission.

How to start seeds indoors: a step-by-step guide

Step 1: Gather your seed starting supplies.

Seeds

Seed starting pots or cell trays

Plant markers

Seed starting mix (homemade or store-bought)

Seed tray with humidity dome (often called a 1020 plant tray or propagation tray, or use any DIY drainage tray with plastic wrap)

Spray bottle or squirt bottle filled with water

If you’ve already made your recycled newspaper pots, you’re all set. If you’ll be using other seed starting pots or cell trays, make sure they’re clean.1

You can also repurpose household items into seed starting containers, like egg cartons, Dixie cups, and yogurt cups. Just wash them out and poke a few drainage holes in the bottom with a nail or an awl.

Step 2: Fill your pots or trays with seed starting mix.

Dump your seed starting mix into a large tub or bucket, pour in a generous amount of water, and stir it up with your hands or a trowel.

As the seed starting mix starts to absorb the moisture, add more water as needed. (This will take several minutes, as peat-based seed starting mixes are slow to absorb.) You want the mix to be uniformly damp, like wet sand.

Fill your seedling pots with this pre-moistened seed starting mix.2

Step 3: Sow your seeds.

Place two to four seeds on the surface of the seed starting mix, and gently press the seeds down so they’re nestled in nicely.

If your seeds are very small, like basil or mustard, you can leave them uncovered.3

If your seeds are larger (like beans or peas) or they require darkness to germinate (check the instructions on the seed packets), cover them with a layer of vermiculite or seed starting mix equal to their height, usually 1/4 inch to 1/2 inch.

Step 4: Label your newly planted seeds.

Label each pot. Trust me, you will never remember what you planted where, as most seedlings look the same at birth.

At this early stage, cheap plastic plant markers work very well and stay out of the way, so save your big and beautiful metal plant markers for the garden.

Step 5: Keep your seeds moist and warm.

Mist your seeds with water.4

Assemble your pots in a seed tray (or reuse a disposable aluminum roasting pan, a baking pan, even that plastic clamshell that your salad greens came in) and cover with a humidity dome (or just plain old plastic wrap).5

If your dome has vents, keep them open to help with air circulation during the sprouting period.

Now, you need to add heat. Since sunlight is not essential at this point, your seed trays can be placed wherever it’s warmest in your house, such as an attic, bathroom, laundry room, or kitchen.6

If your seedling pots stay covered in a warm nook, the low humidity will keep your seeds happy until they sprout. High humidity will make them sad. Only spritz the seeds with more water if the mix feels dry to the touch.7

Within a couple of days to a couple of weeks, the seeds will germinate. As your seedlings start to emerge, some of them will look like they’re wearing little seed hats.

Germination (the process of a seed sprouting) is highly variable, so don’t stress if it feels like it’s taking forever to happen. In most cases, seeds will germinate within three weeks (after that, try starting a new round of seeds).

Step 6: Give your new seedlings light.

At this stage, the newly germinated seedlings need light. Remove the humidity dome or plastic wrap, and move the seedlings to the sunniest spot in your house (preferably a south-facing window).

Continue to keep the mix moist, but not overly wet. Seedlings should be watered once a day or every other day, depending on how much sun and heat they get.

Remember that seedling roots are fairly close to the surface and they’re growing in a small amount of media, so they don’t need a deep soak the way larger plants do.

I like using spray bottles or squirt bottles, as the gentle streams of water won’t displace seeds or damage seedlings.

Step 7: Moving day! Transplant the strongest seedlings when they’re ready.

After your seedlings develop their first “true set” of leaves, they are ready to be transplanted.8

If more than one seed sprouted, choose the strongest one and pinch or snip off the others. You can even keep all of them, but be careful separating the roots if the seedlings are close together.

Transplant the seedling into a larger container filled with potting mix. Hold it by the cotyledons (the first leaves that appear) and try not to manhandle the tiny roots.

At this stage, you can lightly drench the potting mix using a diluted solution of compost tea or all-purpose fertilizer. Keep it simple, keep it organic, and don’t obsess too much over the nutrients.9

Give the seedling plenty of sunlight each day (at least 12 to 16 hours is optimal for most vegetable seedlings) to avoid the “leggy” look. (Learn how to fix leggy seedlings if this is happening to you.)10

Step 8: Harden off those seedlings.

To get your seedling prepped for a good life outside, you can start to harden off the seedling11 by moving it outside under diffused light for a few hours and bringing it back inside each night.

Over the next week, move it from diffused sun to partial sun to full sun, and for longer periods of time, until it’s finally kept outside all night.

Step 9: Transplant your seedlings outdoors.

After the hardening off period, you can transplant your seedling to its final destination, whether straight into your garden or into a larger container.

And then, in a couple of months, you can enjoy the fruits (and veggies) of your loving labor!

More Ways to Start Seeds Indoors

There's more than one way to start your seeds and make sure they sprout!

Germinate Seeds Quickly With Coffee Filters or Paper Towels

Whether you're trying to start tricky seeds with long germination times, or find out if your old seeds are still viable, the coffee filter (or baggie) method is a quick and simple way to start many seeds at once in a small space.

How to Start Seeds in Eggshells, Save Money, and Have Fun

Save those cracked eggshells, upcycle your egg carton, and bookmark this indoor gardening DIY for a rainy day. Starting seeds in eggshells is a fun and easy project that kids will delight in helping with!

How to Soak Seeds to Speed Up Germination Time

If you've had trouble with seeds not sprouting, soaking them in water before you sow them can greatly increase their chances of germinating. This method works well with legumes, beets, squash, and other thick-shelled seeds.

How Long Do Seeds Last? (+ Cheat Sheet on Seed Expiration Dates)

How old is too old? All seeds have a shelf life, but their longevity depends on the quality and condition when you bought or saved them, and how they've been stored since. Find out whether you should keep or toss your seed stash.

1 This seems obvious, but laziness gets the best of us. Clean pots are key and help keep damping off at bay (an untreatable fungal disease that causes seedlings to suddenly keel over and die at the soil line).

Discard or thoroughly wash any pots that previously housed diseased plants. Avoid using leftover soil from the nursery container you brought home, as it might harbor weed seeds and bad bacteria.

If you have a healthy garden, you can skip washing your pots and simply dump out the dirt from your pots before using again.

I’ve put countless seed trays and humidity domes to the test over the years, and found these trays and domes to be the thickest and strongest on the market — they don’t bend, flex, or crack as easily as other brands, and can be reused for many seasons. back

2 It’s easier to start with pre-moistened mix, as peat-based mixes are harder to wet down uniformly if they dry out in pots. Although peat has a very high water-holding capacity once it’s wet, it actually repels water when it’s dry. Go figure.

If you’re not using homemade seed starting mix, this is a reputable brand that I like. You do not need anything fancy; seeds just need a basic mix of perlite, vermiculite, and peat moss (or coco coir) to germinate and grow into healthy seedlings. back

3 For certain varieties of plants, light will often speed up germination (the process of a plant sprouting from a seed). back

4 The moisture will help the seeds shed their protective coating and eventually sprout. back

5 This creates a greenhouse effect to keep your seeds moist and warm, the key to germination. Most annual vegetables germinate best in temperatures of 75°F to 90°F. A few, such as radish, will germinate at lower temperatures.

Seeds will sometimes sprout in less than ideal temperatures, but the germination period will be longer. back

6 I like to put my seed trays next to my heating vent on the floor. Some gardening guides suggest placing your tray on top of a refrigerator, but most appliances these days are energy-efficient and do not give off much heat. back

7 Too much water will make the seeds rot. If your makeshift greenhouse is looking a bit too wet inside, remove the cover or plastic wrap for a few hours during the warmest part of the day to allow air circulation. Mold is no good for seeds, either. back

8 The true leaves are actually the second set of leaves that appear; the first leaves that initially unfurl are not leaves at all, but cotyledons. These leaf-life structures are part of the embryo of the seed, and supply food to the seedling until its true leaves begin the process of photosynthesis. back

9 I like to use home-brewed compost tea or liquid sea kelp. No fertilizer is fine, too, especially if you start with good soil. I have grown healthy vegetables with no fertilizer through a whole season, and could barely keep up with the harvests. back

10 It sounds sexy, but it makes your seedling tall and weak as it channels its energy into straining for sunlight. I also like to gently run my hands across the top of my seedling to simulate a breeze; this slows down initial growth and strengthens the stem. A few brushes a day is all it needs. back

11 Hardening off is the process in which you gradually acclimate the seedling to its future environment outdoors… getting it acquainted with the breeze, the birds, and the bees. back

Continue to Content

The Beginner’s No-Fail Guide to Starting Seeds Indoors

If you're new to seed starting, this foolproof beginner's guide to starting seeds indoors will take you step by step from seed to harvest, quickly and easily.

Prep Time

15 minutes

Active Time

15 minutes

Total Time

30 minutes

Difficulty

Easy

Materials

Seeds

Seed starting pots or cell trays

Plant markers

Seed starting mix (homemade or store-bought)

Seed tray with humidity dome (often called a 1020 plant tray or propagation tray, or use any DIY drainage tray with plastic wrap)

Spray bottle or squirt bottle filled with water

Tools

Large bucket or tub

Trowel

Instructions

Gather your seed starting supplies. Instead of seed starting pots, you can also use recycled newspaper pots, or repurpose household items into seed starting containers, like egg cartons, Dixie cups, and yogurt cups. Just wash them out and poke a few drainage holes in the bottom with a nail or an awl.

Label your newly planted seeds. Label each pot. At this early stage, cheap plastic plant markers work very well and stay out of the way, so save your big and beautiful metal plant markers for the garden.

Transplant your seedlings outdoors. After the hardening off period, you can transplant your seedling to its final destination, whether straight into your garden or into a larger
container.

Did you make this project?

Please leave a comment on the blog or share a photo on Instagram

What to know after your seeds germinate

This post updated from an article that originally appeared on March 19, 2011.

View the Web Stories on how to start seeds indoors.

What Size Is A Standard Seed Tray? (What Does 1020 Mean?) – greenupside

If you are looking for seed trays to germinate seeds for your garden, you have probably seen the phrase “standard size” or “1020”. Although this wording is common, the exact meaning can vary a bit.

So, what size is a standard seed tray? A standard size (1020) seed tray is slightly larger than 10 inches long by 20 inches wide. For example, a standard size seed tray might be 11 inches long by 21 inches wide, with a depth of 2 to 2.5 inches. Sometimes, seed trays have separate compartments (cells) for each seed or group of seeds. This makes it easier to separate the seedlings for transplanting later.

Of course, there are lots of different seed tray sizes available, so a standard 1020 seed tray is not your only option. For example, there are 1010 seed trays and seed trays that will hold round pots, instead of having square cells.

In this article, we’ll talk about standard size seed trays. We’ll also take a closer look at the dimensions available, along with some other common questions about seed trays.

Let’s get started.

(If you want a complete seed starting walkthrough with video and other resources, check out our seed starting course today!)

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What Size Is A Standard Seed Tray (What Does 1020 Mean)?

A standard size seed tray (also called a “1020” tray) is slightly larger than 10 inches by 20 inches (25 centimeters by 51 centimeters), with a depth of 2 to 2.5 inches (5.1 to 6.4 centimeters).

A standard seed tray has a length slightly more than 10 inches and a width slightly more than 20 inches.

The phrase “1020” refers to the tray length and width, which are approximately 10 inches and 20 inches. Often, a standard seed tray will measure a little bit longer in both length and width.

For example, these seed trays from Johnny’s Selected Seeds measure 11 inches (28 centimeters) long by 21 inches (53 centimeters) wide. This gives a little extra space at the edges of the tray, and allows a slightly larger size for individual cells (if present).

As you can see, the seed trays from Johnny’s Selected seeds mentioned above come as one large tray. The trays have no individual compartments (cells) to separate the seeds.

A seed tray without separate cells is perfect for growing microgreens.

This type of tray is a perfect option for growing microgreens. The reasons is that microgreens don’t need their own individual cells.

Instead, the seeds can all grow together on one big “field” of soil mix. (The point of microgreens is to harvest them by cutting off the tops, rather than being transplanted at a later date).

On the other hand, these 1020 seed trays from the Bootstrap Farmer have separate cells for individual plants. This makes it much easier to space out seeds properly.

It also makes it easier to transplant plant plugs without harming the roots of your plants. With each seedling in its own cell, the roots of separate plants will not get tangled up together.

When each seedling has its own cell, roots don’t get tangled and transplant is easier.

There are 50 separate cells in this seed tray (which is 5 cells long by 10 cells wide). The cell dimensions for this seed tray are 1.75 inches by 1.75 inches (4.45 centimeters by 4.45 centimeters), with a height of 2.25 inches (5.72 centimeters).

Each cell has a 0.25 inch (0.64 centimeter) drainage hole, which keeps the soil in the cell from holding too much water. The drainage hole also helps to remove the seedling and soil when it is time to transplant outdoors for spring planting.

You can even place the entire seed tray in a corresponding 1020 seed tray (without compartments). Then, you can water the seedlings from below by adding water to the bottom tray.

That way, you won’t have to worry about over watering any one cell and killing your seedlings before they have a chance to grow.

How Deep Should A Seed Tray Be?

A seed tray should be 2 to 3 inches deep, depending on what you are growing and when you intend to transplant.

The University of Maryland suggests seed trays should be at least 2 inches deep. On the other hand, the University of Iowa suggests using at least 3 inches of soil for starting seeds.

Seed trays should be at least 2 to 3 inches deep. Make sure to make holes for drainage if there are none.

However, according to Johnny’s Selected Seeds, you should avoid trays that are too deep. The reason? You want them to be able to drain well (if the soil stays too wet, seeds can rot, and seedling roots cannot get enough air.)

Your seed tray should be deep enough to hold enough soil for starting seeds, plus a little space on top for watering. Otherwise, the water can run right across the top of the soil and over the edges of the tray.

Seed tray depth also depends on the type of plant and when it will be transplanted.

Deeper trays leave more room for roots to grow deep. They also give you more time before you need to transplant, which can be helpful in cold climates.

Remember that larger seeds need to be buried deeper. You can learn more about how deep to plant seeds in my article here.

Seed planting depth depends on the type of seed.

Of course, you can also repot certain plants (like tomatoes) into larger containers after they outgrow their seed tray cells. This lets you keep them indoors until it is time to transplant outside.

You can use this page from the Old Farmer’s Almanac to find the last spring frost date in your area to get an idea of when to transplant outside.

Do 1020 Seed Trays Need Holes?

A 1020 seed tray should have holes to allow for proper drainage. Otherwise, the soil will stay too wet.

This can lead to seeds rotting before they germinate, damping off of seedlings, or root rot (which occurs when wet soil prevents roots from getting air).

Seedlings may suffer from damping off if they get too wet.
Image courtesy of:
INAKAvillage211 from:
https://commons.wikimedia.org/wiki/File:
Pinus_taeda_seedling_
damping_off_(cropped).jpg

What Other Seed Tray Sizes Are Available?

There are lots of other options if you decide to buy a seed tray with different dimensions or cell counts.

For example, you can find seed trays with as few as 4 or as many as 200 cells!

You can choose from lots of different types of seed trays, including ones that hold several larger circular pots.

Let’s explore a few of these seed tray sizes in more detail.

1010 Seed Tray

A 1010 seed tray has dimensions slightly larger than 10 inches by 10 inches (25.4 centimeters by 25.4 centimeters). These trays are square, and they are often compatible with 1020 trays.

That means you can fit two 1010 seed trays side by side on a 1020 seed tray.

A 1010 seed tray is slightly more than 10 inches long and 10 inches wide.

These 1010 seed trays from the Bootstrap Farmer also have drainage holes to prevent over watering or to allow watering from a reservoir below the tray.

The tray dimensions are 10.5 inches long by 10.5 inches wide by 2.5 inches deep (26.7 centimeters long by 26.7 centimeters wide by 6.4 centimeters deep).

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1020 Net Pot Tray

If you want to grow plants in separate round pots for either hydroponics or traditional soil gardening, then the 1020 Net Pot Tray is a good option.

A 1020 net pot tray will hold 32 2-inch round pots – a good option if you want to give your seedlings more room and time to grow indoors.

Instead of square cells, these trays have circular holes to hold individual round pots. These pots are larger than the standard square cells.

The larger pot size allows you to give seedlings more room and more time for growth indoors. This helps to offset late spring frosts or a short growing season, which are common in northern regions.

This 1020 Net Pot Tray from the Bootstrap Farmer fits 32 2-inch round pots. The tray is 4 pots long by 8 pots wide, with the cells spaced about 0.5 inches apart.

These net pot trays fit perfectly into a standard 1020 tray, which allows for watering from below (if using traditional soil gardening). It can also be used in a soilless growing setup (such as hydroponics, aquaponics, or aeroponics).

6 Cell (2×3) Plug Tray Inserts

These smaller 6 cell trays from Bootstrap Farmer are perfect if you want to keep different plants in separate trays, but grow them in the same place.

Each cell in the tray is 1.5 inches by 1.5 inches (3.8 centimeters by 3.8 centimeters) at the top, tapering down to 1 inch by 1 inch (2.5 centimeters by 2.5 centimeters) at the bottom. The height is 2.25 inches (5.7 centimeters).

The inserts are designed so that 12 of them will fit in a standard 1020 tray, allowing for watering from below.

What Are The Best Seed Trays?

In my opinion, some of the best seed trays are made by Proptek. Their seed trays are made from a durable black plastic that won’t decay or break down in sunlight.

This is helpful for dedicated gardeners who want to start seeds indoors year after year. It is also nice for budget-conscious gardeners who do not want to pay for new seed trays every year.

Proptek sells their sturdy 162-cell seed trays on their own website, but you will need to buy them in bulk if you go that route. You will need to ask about pricing, and they have a certain minimum order quantity.

On the other hand, you can also buy 162-cell Proptek seed trays (and other sizes) from retailers such as Greenhouse Megastore.

Humidity Domes For Seed Trays

A humidity dome is a plastic cover used to trap moisture in a small area so that seeds can germinate better. Humidity domes are sized to fit the corresponding seed tray dimensions.

For example, this 1020 humidity dome from the Bootstrap Farmer will fit over a standard 1020 seed tray.

Humidity domes are helpful because they make it easier to maintain high humidity levels in soil for germinating seeds. They can also keep seeds or seedlings warmer by producing a “greenhouse effect” if you have a grow light setup above your seed trays (which might be a good idea, since seedlings need light to grow).

For more information, check out my article on humidity domes.

One word of caution is necessary. Be careful about mixing and matching trays and humidity domes.

If you buy equipment from different companies, there can be slight differences in dimensions. Sometimes, these differences mean that a dome or insert will not quite fit a tray.

Another (Non-Tray) Indoor Growing Option

There is another option for growing indoors, which is a little bit different from the seed trays we have discussed so far. This alternative method is the grow bag.

A grow bag is made of durable fabric material, such as canvas. It is used to hold soil and plants.

A grow bag is made from a fabric material such as canvas or burlap.

A grow bag can be used to grow either one large plant or multiple smaller plants. Larger grow bags can even be used to hold dwarf fruit trees, or to get larger fruit trees started indoors.

Grow bags can be used indoors or outdoors, or even planted directly in the ground. Grow bags prevent plants from becoming “root-bound” as they do in standard plastic or clay containers.

They are reusable, and can last for years if given proper cleaning and care.

You might be able to use a shallow grow bag to start seeds indoors, as an alternative to a plastic seed tray.

For more information, check out my article on why to use grow bags.

How Many Seeds Should You Put In Each Cell In A Seed Tray? (How Many Seeds In A Seed Tray?)

For seeds with a high germination rate, you really only need one seed per cell in a seed tray. In a 162-cell tray, a 95% germination rate means you will only have about 8 empty cells (where the seeds failed to germinate).

Remember that older seeds will have a lower germination rate. Some seeds will only remain viable for a year!

If your seeds have a low germination rate, I would suggest planting two seeds per cell in a seed tray. That way, there is a very high chance that at least one seed in each cell will germinate.

This means that you won’t have many, if any, empty cells. However, in order to avoid competition between plants, it is a good idea to “thin” the seedlings by removing any extra ones.

If two seedlings start to grow in one cell, wait for a few days and observe them. Then, leave the stronger one to grow and pull out the weaker one.

If two seeds sprout in a cell, it is better to leave the strongest one and remove the others.

It seems cruel, and it can be difficult for gardeners to do this! However, if you don’t thin the seedlings, then the roots of the two seedlings will become intertwined.

This makes it difficult to separate them out for transplanting later. Even worse, the two seedlings will compete for resources (water and soil nutrients).

Ultimately, this will lead to two plants that are both smaller and weaker than one dominant plant would have been. So, make sure to thin your seedlings when the time comes!

What Happens If You Plant Seeds Too Close Together?

If you plant seeds too close together, you will see overcrowding & competition in your seed trays. The roots of separate plants will become tangled together, making it difficult to separate them out later.

This makes it much more likely that the roots of some plants will be damaged during transplant. In turn, this will cause more of your plants to wither and die when exposed to the harsher conditions outdoors when you try to harden them off in the spring.

You can avoid this problem if you use seed trays with separate cells (as long as you thin the seedlings when two or more grow in a cell.)

If your seed tray does not have separate cells, then you will need to make sure that you use proper spacing for the seeds. Check online or look at the seed packet to find the recommended seed spacing for the plants you are growing.

This table from the USDA (on page 2) gives some suggestions for cell sizes for starting seeds of various types, including:

Broccoli

Lettuce

Onions

Peppers

Tomatoes

The planting depth for seeds depends on the type of plant.

Conclusion

Now you know what size a standard seed tray is, and you also know what the cryptic phrase “1020” refers to. In addition, you know about some of the other options available for seed tray dimensions.

If you want to learn more about seed trays, how to water them, and how to make your own, check out my article here.

You can find answers to some common questions about seed trays here.

You can also learn about more ideas for making your own seed trays in my article here.

You can also try using soil blocks as an alternative to seed trays – you can learn more here.

I hope you found this article helpful – if so, please share it with someone who can use the information.

To find books, courses, seeds, gardening supplies, and more, check out The Shop at Greenupside!

Seedling Trays: Everything You Need To Know About Propagation Using Seedling Trays

A seedling tray is a container used to sow multiple seeds at once. After seed germination, seedlings grow in the seed tray until they are large enough for transplant. A single seed tray can hold anywhere from 6 seeds to over 1000 seeds.

Parts Of A Seed Tray

There are two basic parts to a seed tray, one of which is optional:

Tray

– this is the outer part that holds soil, individual containers (pots), or a cell flat. When used with a cell flat, the tray is used for watering from below.

Cell flat (plug flat)

– this is the optional inner part. You can put a cell flat inside of a tray to separate seeds from one another.

seedling trays can come in different forms;

Mesh seed tray

– a mesh seed tray allows water to drain out easily. A mesh seed tray is best for holding multiple individual containers (pots). A drawback is that the holes in a mesh seed tray are too large to hold soil without it falling through or washing away when watered.

Solid seed tray with drainage holes

– a solid seed tray with drainage holes allows for adequate drainage, but allows soil to stay moist enough for seed germination. A solid seed tray with drainage holes is best for planting multiple seeds together in one place. A drawback is that the seedlings do not have individual cells, so their roots can get tangled together as they grow.

Solid seed tray without drainage holes (leak proof seed tray)

– a solid seed tray without drainage holes does not allow for any drainage. A solid seed tray without drainage holes is best for holding a cell flat. Since it holds water, it can be used to catch excess water from watering seeds, or it can be used to water from below.

A cell flat (or plug flat) is a container that is divided into multiple cells. Some common cell counts for seed trays are:

50 cell seed tray

72 cell seed tray

128 cell seed tray

200 cell seed tray

288 cell seed tray

​​50 cell seed tray

These trays are a happy medium of saving you space in your seed starting area while still being able to plant a large number of seedlings like lettuce that will be directly transplanted. Because the 50 cell tray has a much larger soil volume than the 72 cell plug trays or 128 cell trays, you will have a bit more wiggle room when you need to transplant for optimal root growth. Plants grown in these trays will be less likely to become root-bound if unsettled weather delays your planting. This size also allows for canopy development of the seedling.

72 cell seed tray

The 72 cell seed tray are the most popular choice amongst market gardeners. They are a good balance between space for growing and seedlings per tray. Each cell is 1.5″ square and 2.25″ deep, making them an excellent option for a large variety of plants. These plastic trays are also a good choice for vine plants. However, you will want to transplant the vine plants earlier than you would with the 32 Cell trays to prevent root bound seedlings.

128 cell seed tray

These 128 Cell Trays are a great choice if you wish to start row crops or many baby greens. This configuration is ideal for starting many seeds but is not meant for crops that need more than a few weeks. Each cell is 1″ square and 2.25″ deep. You will be able to plant 78% more seedlings with one tray than the more common 72 cell seed starter trays. These 128 seed trays are compatible with the heavy-duty 1020 deep tray for bottom watering. You will want to up-pot your seedlings from this size seed tray into a larger pot or grow bag if you do not plan to transplant outdoors for an extended period to prevent seedlings from becoming root-bound.

200 cell seed tray

These 200 Cell Trays are excellent trays if you want to be economical about growing cole crops, lettuces, and other small-seeded crops. You will be able to grow 2.8 times as many plants with one tray as you would with a 72 cell tray. Each cell is 0.75″ square and 2.25″ deep.

If you are using 200 cell plastic trays to start seeds, you will need to transplant your seedlings at an earlier stage. Typically once they have one, at most two sets of true leaves. This plastic tray size is most frequently used by larger-scale farmers and those who intend to pot up their seedlings multiple times before moving outside.

Factors to consider before using seedling trays

Specification of seedling tray

The common seedling tray size is 540mm x 280mm with different cells. The less the number, the larger the cell. The numbers of cells are 50, 72, 105, 128, 200, etc. The selection of plug tray specifications should not only consider the size and shape of the seeds, but also the size of the young plant. Only by selecting the proper size can the seedlings achieve optimal growth.

Hole shape of seedling tray

There are two shapes of holes in seedling trays: round and square. The round hole has a smooth inner wall, without corners of the square hole, which is conductive to the winding of the root of the plant on the inner wall. The square hole is good for guiding the roots to extend downward, and the substrate capacity is about 30% more than the round one. The water is distributed evenly and the roots can grow better.

Thickness of seedling tray

The thickness of the common seed trays on the market is 0.6 to 1.2 mm. 0.6-0.8 thickness plug trays are mostly used for manual sowing or one-time use, for example, if selling the young plants with seed trays, the seedling company can choose 0.6-0.8mm thickness trays. 1.0~1.2 mm thickness trays are suitable for machine sewing and reuse after disinfection.

Depth of seedling tray

The depth of the seed tray on the market is 3-5 cm, the deeper the tray depth, the larger substrate quantity and the greater the substrate water retention, then the more conductive to roof growth. There are also special-purpose seedling trays with a depth up to 9-11 cm.

Suitable trays for vegetable and fruit seedlings

Generally, a 50 cell tray is fixed for fruit plant seedlings, such as cucumbers, melon, watermelons, pumpkins, etc. The 72 cells one seedling tray is mostly for vegetable propagation, such as eggplant, tomatoes, etc.

105 cells and 128 cells are mostly for leafy vegetable propagation, such as lettuce, cabbage, kale, spinach, cabbage, broccoli, etc.

Material of seedling tray

At present, the seed trays used for seedling cultivation mainly include plastic seed trays and polystyrene foam trays. The main materials of the plastic plug are polystyrene (PS), polyvinyl chloride (PVC) and polypropylene (PP). The polystyrene is resistant to high temperature, not easy to deform in summer, has good toughness, and does not break easily in harsh climates.

Benefits of using seedling trays

There are many advantages to using a nursery tray as opposed to other solutions, like growing in larger containers. It is incredibly simple to handle, sow, and plant seeds, and it also makes transplanting easier as seedlings grow. If you want to improve your chances of growing healthy plants and make sure they have enough room to grow and thrive as they should be anticipated to do when they become fully grown plants in only a few months or years from now, it’s crucial to utilize nursery trays. The benefit of employing a nursery tray is that seeds can be sown indoors under the safety and supervision of a grower. Here are some of its benefits:

Grow a variety of plants

Improve Germination success rate

Fertilize easily

Excellent water drainage

Effectively manage the temperature

Transferring plants to larger containers is simple.

Boosts productivity

Saving money

Mazero Agrifood ltd has a variety of quality seedling trays that are of high quality and cost effective. Contact us today on +254729777711 to order.