The Best Seed Starting Trays For Beginner Gardeners

02 Sep.,2024

 

The Best Seed Starting Trays For Beginner Gardeners

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Seed starting trays are one of the easiest ways to start vegetable, flower, and other plant seedlings indoors before the weather warms up. They come in a variety of sizes, with different features, and materials, but which ones are best?

Are some seed starting trays better then others and why? This is what I set out to find out this years growing season, in my quest to grow more of my own vegetables at home!

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Are Seed Starting Trays Absolutly Necessary?

In past years, I never really used seed starting trays and always went with a collection of mixed solo cups, old flower pots , yogurt containers, egg cartons, basically whatever I could find and put soil in! While all these containers do work, and can be a great way to garden on a budget, I never really found that much success with my mix and match approach.

The main problem with this approach is that it simply makes things harder to manage. The various containers all require different amounts of water to stay moist, they take up way more space, and you have to move each seedling individually should you want to move them out, under grow lights or into a new window sill.

In short, are seed starter trays necessary for the beginner gardener? No, not exactly, but they sure do make life a whole lot easier, and dramatically improve your chances of success!

Why would we recommend using seed starting trays?

Seed starter trays make life a whole lot easier by conveniently grouping seedlings into easy to manage trays.

  • It is much easier to provide adequate lighting when all the seedlings are grouped closely together instead of being spaced out in various size containers. The trays easily fit under grow lights, and can easily be moved around as a group.
  • As the seed tray cells are all a uniform size, it is much easier to water, and stay on top of the moistures requirements of the various seedlings. As the seed trays all contain proper drainage, they also help prevent over watering the seedlings.
  • It is much easier to plant similar types of plants in their own trays, for example herbs in one, lettuces in another, etc. This helps when needing to harden off or transplant certain seedlings before others.
  • Some seed trays even come with clear plastic covers or domes, which help regulate moisture, especially in the beginning phases of germination and growth.

Different Seed Starting Tray Materials and Designs

Most often seed starting trays are made of rigid plastic and are reusable, or are made of super thin recyclable plastic that is meant to be thrown away after using. Some are a combo of plastic drip tray with bio-degradable cells or peat pellets that can later be planted right into the garden.

There are a wide range of designs to choose from, and it can be overwhelming, especially for new gardeners.

Which you'll end up choosing depends on several factors and we'll go over some of the most common designs in this guide to help you decide what will work best for you.

Seed Tray Sizes

Most seed starter trays come in a 10" x 20" size, but differ in the amount of 'cells' or individual plants that can be planted in the tray.

The more cells a tray has, the shorter the time frame before the seedlings out grow the tray and need to be planted out or transplanted into larger containers.

Tray sizes range from 12 cell trays - 128 cell trays! In my experience, tray sizes between 24 cells and 48 cells work best and will safely keep your plants indoors for 4 to 8 weeks before needing to be transplanted.

  • Trays with a high number of cells (and thus a shorter growth time indoors) work especially well for lettuces such as spinach, kale, and head lettuces, which can be transplanted out into the garden sooner, either under hoop tunnels or in cold frames, then other plants.
  • Trays with a smaller number of cells (for example 24 - 36 cells per tray) are ideal for plants such as tomatoes, cucumbers, bell peppers, herbs, and squashes.

Root vegetables, should when possible always be planted directly in the garden and not transplanted.

If you see roots coming out of the cells or peat pellet inserts, it's time to transplant the seedlings into a larger container or into the garden.

Bio-degradable inserts vs plastic cell trays

Which style of seed starter tray you choose is ultimately up to you.

Bio-degradable cell inserts are great, and make transplanting easy as the entire 'cell' is simply transplanted directly into a larger container or into the garden, and the tray material bio-degrades. They do need to be replaced yearly though and have a tendency to develop mold easier then plastic cell trays do.

Plastic seed starter trays are mostly re-usable, especially the more rigid plastic celled trays. The seedlings can be slightly harder to remove from the trays at transplanting time though, and you may need to use a butter knife, or spoon handle to help loosens the sides of the individual cells.

Never pull on the seedling stems to try and remove the cell from the tray as you will most probably damage the plant!

Additional accessories for your seed trays

Consider these accessories when starting and growing seedlings indoors. They make life a whole lot easier, and increase your chances of success! If you have to pick just one of them, I will always recommend grow lights be the first upgrade to your indoor seedlings!

  • LED Grow Lights- specially designed lights to provide the proper amount of lights seedlings require to prevent growth issues.
  • Heat Mats- help by keeping soil temperatures consistently warm, speeding up and aiding in germination rates.
  • Base Trays- provide drainage for trays with drainage holes, and allow you to water your seedlings from below. Tis can help prevent disease and pest problems!
  • Clear Dome Lid- Help keep heat and moisture in the seed tray. Especially important when waiting for seeds to germinate. A great and cheap investment when heat mats are not possible.

The Best Seed Starting Trays For Beginner Gardeners

In our quest to discover which seed trays work best for our vegetable garden needs, we purchased and trialed three of the most commonly available styles of seed starting trays. Biodegradable cell inserts on a plastic base tray, peat pellet inserts with a base tray, and a rigid plastic celled tray with a base for watering.

Jiffy Professional Greenhouse 72-Cell Starter kit

Review:

A great seed starting tray for beginners, just add water and the peat pellets expand. No need for extra potting soil, or filling pots. Seeds sprout quickly and the clear heat dome helps retain moisture, reducing the need to water as often. Downside to this size tray is the short growing time before the seedlings need to be moved to larger pots or transplanted into the garden. Plan accordingly. Perfect for lettuces or plants that can be transplanted within a week or two of germination.

Pros:

  • Easy to plant peat pellets
  • Comes with clear lid to retain moisture
  • Comes with base tray for easy watering
  • No need to purchase potting soil

Cons:

  • Seedlings quickly outgrow the peat pellets
  • pellets need to be replaced after each use
Check Price On Amazon

32 Cell Peat Pot Strips

Review:

Large peat pots provide enough space for plants to grow for 6 to 8 weeks. Perfect for tomatoes, peppers, cucumber, or squash seedlings. Base tray allows for easy watering, though care must be taken not to overwater to prevent mold growth. We found cutting the strips apart before planting made transplanting easier, with less disturbance to the plants. A great, easy to use tray for most plants.

Pros:

  • Bio-degradable inserts make planting and transplanting easy
  • Larger cell size allows for seedlings to stay indoors longer nd develop healthy root systems
  • Comes with base tray for easy watering
  • Allows for longer growth time before transplanting

Cons:

  • Inserts need to be replaced yearly
  • Requires a solid watering tray (sold separately)
  • Requires potting soil to fill.
Check Price On Amazon

Re-Useable 72 Cell Plug Tray

Review:

The re-useable nature of this seed tray requires only adding new potting soil before each use. The deep 1.8 inch plugs allow for more root development despite the high cell count. We found the seedlings to easily grow for up to 4-6 weeks before requiring transplanting. Perfect for herbs, peppers, lettuces etc. Plugs are harder to remove at transplant time though and require loosening of the sides with a spoon or popsicle stick, increasing the chances of damaging roots.

Pros:

  • Entire plastic tray is reusable
  • Each cell has dedicated drainage hole
  • Deep 1.8" cells allow for more root development.

Cons:

  • requires base tray for drainage
  • seedlings are harder to remove then with bio-degradable inserts or pellets
Check Price On Amazon

Summary

Over all we found that all three styles of seed starting trays had their own pros and cons making them great for different things. With all trays we tried, we found planting 2-3 seeds per cell and then trimming back to just one seedling after sprouting to give the best results.

The small Jiffy peat plugs where great for starting lettuces, herbs, and brassicas that can be transplanted out sooner even in cool weather. Tomatoes and cucumbers struggled in these peat plugs due to the limited growing space for the roots and required transplanting into larger pots fairly quickly.

The larger 32 peat pots where wonderful for plants that require more time to establish before being planted out. Tomatoes, cucumbers, herbs, and squashes all did well in this tray for up to 8 weeks. The only downside was the need to separate and space out some of the plants once they grew so large they where shading the other seedlings.

The re-useable 72 cell tray with 2 inch plugs worked surprisingly well, even for our larger plants, such as tomatoes and peppers. The deeper cell plugs allowed the plants to stay in the trays longer then expected. Removing the plugs without damaging the roots was a bit of a challenge though and took some getting the hang of.

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My new favorite seed starting supplies

I finally bought reusable seed starting trays to replace the flimsy black plastic ones that crack apart after a single season. The new seed starting trays are silicon, can be sanitized in the dishwasher, and come with humidity domes and built in mini grow lights.

The cost is pretty affordable as well, coming out to about $0.50 cents per plant. I plan to use these for the next 10 years or more, which means they would come out to about $0.05 cents instead!

My current seed starting setup

I bought these colorful silicon seed starting trays this year - both for fun and function. They sit adorably in the window, making me smile every time I walk by. As a bonus - they are as practical as they are cute.

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Why use silicon seed starting trays

Silicon seed starting trays have recently started popping up and are gaining popularity over the standard paper-thin black plastic trays you find at nurseries. Those plastic trays crack after one use and can get a bit toasty on a seedling heat mat.

The silicon trays are flexible, making it easy to push on the bottom to pop the plant out for transplanting. They can also be placed in the dishwasher for easy sanitizing year after year.

Why these trays

After browsing through all of the silicon seed starting tray options on Amazon and nursery websites, I settled on these trays from Amazon. I think you get a lot for the price and the quality is high.

I bought the 8-pack of silicon trays that each come with a thick plastic bottom, and a tall 4" humidity dome with mini grow lights built in. It also comes with 80 plant tags and a couple mini plastic tools for punching holes in soil or scooping soil. Each tray has 9 cells for a total of 72 cells.

Product details

I took measurements of the seed starting trays in case you are trying to fit them on a windowsill, a standard tray size, or trying to determine what to use for your seed starting medium.

  • Silicon tray is exactly 5" x 5"
  • Cell interior is 1.5" x 1.5"
  • Silicon tray height: 2.25"
  • Plastic tray: 5.75" x 5.75" to edge of lip, and 4.75" x 4.75" across the bottom
  • Plastic tray height: 2.75"
  • Dome: 4" high
  • USB cable to power grow lights: 14" long

The 8-pack of silicon trays comes with 4 USB "double" cables to power the grow lights. Each cable splits into 2 cords and each of those cords is 14" long. I bought a $15 USB power strip to plug them in.

Everything you need for seed starting is listed at the bottom of this post, in one place.

Seed starting mixes

In my experience, the most important factor for successful seed starting is finding the right soil or growing medium. This can make germination easy or near impossible, depending on what you choose. The two easiest seed starting options are Horticubes and OrganiPlugs. Seed starting soil mixes are also a good option.

Seeds need to stay moist in order to germinate. It might seem like you can simply pick any soil and keep it watered, but too much water without drying out invites mold. Mold can stunt or kill the seedlings.

Seed starting soil mixes are formulated to hold moisture, often including perlite or peat, which is a good thing! But I've found soil to be too finicky for seed germination for my liking. It seems too easy to underwater, resulting in poor germination, but overwatering often leads to mold growth on the top. I know other people who have had more luck with soil mixes or soil blocking.

This year I'm trying out OrganiPlugs and they've worked out well so far. They are made of peat and coco coir and feel quite spongy. They stay moist and so far I haven't run into mold problems (and don't expect to).

OrganiPlugs are made to fit into standard seed starting trays. They fit almost perfectly in each cell of the silicon trays I bought - they have just a little bit of wiggle room.

I'm also using Horticubes for herbs this year. They don't fit in the silicon trays, instead they are meant to sit in a large tray then get transplanted shortly after germination.

(All of the products are also listed at the bottom of this post in one place).

Alternative seed starting options

I have a couple other options to suggest if for some reason you don't want to share in the joy of these cute, resusable trays!

Upcycle disposable containers

Empty yogurt, fruit cup, or applesauce containers make great seed starting pots - just be sure to drill a few holes in the bottom. Leftover take-out containers work well as a tray to collect the draining water.

When upcycling containers, you'll likely need to use a seed starting soil mix. If you do this, be sure to check the moisture levels several times a day so it doesn't dry out, or stay too wet.

OrganiPlug pre-filled tray

OrganiPlug offers a 50-cell tray pre-filled with their OrganiPlugs. It doesn't get much easier than that. However, the tray will likely only be usable for 1-2 years as the thin plastic will crack as you remove the plants for transplanting.

Oasis Horticubes

I actually use this seed starting method every year, including this year - Horticubes. They are the most reliable and easiest seed germinating medium. I really can't stress how easy these are to use.

These feel like foam but are made from biodegradable materials that will continuously break down over the course of the year. It's sterile medium so it won't transfer pests or diseases.

Horticubes hold water extremely well and don't mold. Seed germination is easy and all but guaranteed. I never run into problems when using Horticubes.

The downside is they are very small and offer no nutrients. That's fine for germination but they will need to be transplanted to larger containers as soon as their first set to true leaves shows up. If you don't transplant, they just stop growing (I know, because I've done it!)

I use these every year for starting herb seeds where I want a bunch of each type of plant. Once they sprout, I transplant them to a larger tray with soil that I continue to water. When they are ready to be transplanted outdoors, I break apart the roots if they've grown together and set them in their sunny spots!

One note worth mentioning is the sheets that arrive are fragile. They can easily break apart if you aren't careful or if shipping was rough.

Get Horticubes on Amazon or Harris Seeds for a similar price.

Other options

There are a few other options to consider - rockwool, foam plugs, and seed starting soil mixes. I don't think these options are as good as the ones listed above, however.

Rockwool is made from molten rock that is spun into threads to create the product. I used rockwool cubes a while back but stopped when I learned it might be harmful to the lungs.

It's too bad because they are a fantastic medium. They are relatively cheap ($0.10 per cube or less), hold water extremely well, and never mold. Seed germination in these is outstanding.

Some people still use them, and I don't feel like I've found enough credible evidence to confidently advise against using these. I personally don't use them because I prefer to err on the side of caution, and I've found other alternatives.

Foam plugs are another option. They actually work quite well - they hold water, don't mold, and are affordable. But I personally don't use them because they don't compost into the soil, leaving little spongy plugs around.

Seed starting soils are formulated specifically for seed starting. They often contain perlite, peat, and coco coir to hold water. As I mentioned earlier though, I always have trouble with either over watering and getting mold problems, or underwatering, resulting in poor germination.

If you've had luck with seed starting soils in the past, then I see no reason you wouldn't continue to have success. It's a good, affordable option!

Where to buy

Amazon is actually a great place for seed starting supplies. I find their prices are often much lower than online seed websites and even hardware stores. The links in this article are affiliate links, which means I get a small commission if you make a purchase (and a big thanks if you do!). In return, I only recommend products that I personally use and feel good recommending.

Everything you need for seed starting with my silicon tray setup:

Alternatives

Extras:

Seeds need warmth to germinate, so most people set them on a little heat mat. Once they germinate, remove them from the heat mat and leave them at room temperature.

The heat mats get slightly warmer than room temperature, and the inexpensive ones don't have controls other than being plugged in or not. Mine are all like this and were very inexpensive (small ones are around $15). This 10x20" heat mat will fit the 8 silicon trays (they might hang off the edges a little). I don't have this one in particular because I bought mine over 10 years ago. It has good reviews and looks exactly the same as what I use.

Alternatively, set your seeds on top of your fridge to germinate. It's just warm enough to lend a helping hand instead of a heat mat.

Where to buy seeds

I bought seeds from a dozen vendors last year. In part it was to evaluate vendors since so many people ask me for my favorite sources. But part of it was chasing unique varieties that only one or two vendors sold.

I share a dozen of the best places to buy seeds, from incredibly cheap sources for $2 or less, to fully organic but more expensive. I also have a good source that specializes in each specific climate, including the Pacific Northwest, West Coast, Southwest, Southeast, Midwest, and Northeast.

For information on how to start your seeds, Swanson Nursery has a good tutorial.

Store your seeds in a binder

4-pocket binder sheets fit seed packets perfectly. The smallest pack you can buy seems to be 25-30, which gives you 100-120 pockets. When storing them back-to-back (one faces front, one faces back), you get double the storage for 200-240 seed packets. I bought a 50-pack and it was way too many - oops.

I also bought a 1.5" thick binder which was definitely too small. I would definitely recommend a 3" ring binder, especially if you are storing large seeds like beans, peas, and corn.

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I've been gardening for almost 2 decades across the country in several different climates. I've been writing detailed guides to answer your questions, from where to buy seeds to how the heck does asparagus actually grow?

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