The Best Soil for Seedlings - Our 2021 Review
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The Best Soil for Healthy Seedlings

I’ve eagerly been testing seed starting mixes, potting soil, and many other gardening supplies this year to up my game even more. Last year, I didn’t have as much success germinating seeds as I hoped for. My herbs mostly did great, but the flowers – oh, the poor colorful blooms that never were!

So to make things more successful, deeper research, a better understanding of what seeds need, and searching and reviewing the very best soil for seedlings have brought us here. You’ll find my list is composed of various types of starter mixes, from coconut coir to all-purpose and everything in between. One of them is bound to do the trick for whatever you’re getting started on for your garden this year.

Backyard Boss Top 5 Soils for Seedlings in 2021

PRODUCT FEATURES
Miracle-Gro Seed Starting Potting Mix - The Best Soil for Healthy SeedlingsMiracle-Gro Seed Starting Potting Mix
  • Number of quarts: 8
  • Key ingredients: Soil mix with Miracle Gro plant food
  • Organic: No
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Jiffy Natural & Organic Starter Mix - The Best Soil for Healthy SeedlingsJiffy Natural & Organic Starter Mix
  • Number of quarts: 12
  • Key ingredients: Canadian Peat Moss
  • Organic: Yes
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 Birchseed Soils Sphagnum Peat Moss Soil Conditioner, Potting Soil, Soil Amendment & Media - The Best Soil for Healthy Seedlings Birchseed Soils Sphagnum Peat Moss Soil Conditioner, Potting Soil, Soil Amendment & Media
  • Number of quarts: 1
  • Key ingredients: Sphagnum Peat Moss
  • Organic: Yes
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Burpee Organic Coconut Coir Concentrated Seed Starting Mix - The Best Soil for Healthy SeedlingsBurpee Organic Coconut Coir Concentrated Seed Starting Mix
  • Number of quarts: 16
  • Key ingredients: Coconut coir
  • Organic: Yes
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Window Garden Expanding Organic Fiber Soil - The Best Soil for Healthy SeedlingsWindow Garden Expanding Organic Fiber Soil
  • Number of quarts: 10 or 12
  • Key ingredients: “Fiber soil
  • Organic: Yes
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Why You Can Trust Us

Gardening is in our blood here at Backyard Boss. I’ve been around plants all my life, with parents and grandparents working on farms their wholes lives, working as Soil Conservationists, and gardeners. I’ve been doing gardening myself since I was young, helping my dad grow tomatoes and fruit trees in the sandy soils of Florida. Now, I’m creating my own urban garden in Illinois where I need the best soil, seed starters, grow lights, planters, and so much more.

As I research, experiment, and learn for my own garden, I’m privileged to share all that work with you to make your journey easier and more successful from the start.

Best for Seed Starting

Miracle-Gro Seed Starting Potting Mix
    Miracle-Gro seed starting soil mix infused with plant food

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Why We Like It: Not only is Miracle-Gro one of the most well-known brands in the gardening business, but its products are some of the absolute best around. This seed starting mix is a prime example of their great products, providing your plants with soil that’s already infused with plant food for easier care and faster growth.

The mix is created with a soil blend designed specifically for germinating plants and encouraging root growth that’s quick and easy. The plant food infused into the soil makes it easier for you, too, as you don’t need to add additional compost or food as the plants begin popping up. It’s especially great for both growing plants from seeds and cuttings alike.

Who Should Buy It: Anyone who’s not totally garden savvy or has an awkward schedule (or travels) will find this seed starting mix a great option. Ideally, use it for flowers and inedible plants.

Best for Organic Seed Starting Mix

Jiffy Natural & Organic Starter Mix
    Organic potting soil mix for new seeds from Jiffy.

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Why We Like It: This easy-to-use soil is a fantastic organic option for folks looking to get their seeds started in organic soil that’s blended for the perfect pH balance for growth. It’s made with a uniform blend that’s balanced and consistent and encourages seedlings to pop up quickly (with or without fast-growing seeds). And since it’s organic, it’s safe for herbs, vegetables, and fruit you intend to eat.

The blend is made with professional gardening in mind with casual gardening ease of use. It requires specific drainage and proper planting techniques to encourage plant growth and safely grows edible plants.

Who Should Buy It: This seed-starting soil is ideal for anyone looking to do some organic gardening with a general potting mix. It will start the seeds quickly and ready them for transfer to the garden bed or container garden.

Best With Sphagnum Peat Moss

 Birchseed Soils Sphagnum Peat Moss Soil Conditioner, Potting Soil, Soil Amendment & Media
    Sphagnum peat moss mix for seedlings.

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Why We Like It: The unique preparation of this Sphagnum Peat Moss makes it a great choice for starting your seeds the right way. The quality media promotes aeration, retains moisture, and encourages fast growth from your seeds.

The 100% organic moss medium has exceptional soil structure for the needs of your seedlings, and blends well with perlite or other soilless mixes for seed starting, as needed. It’s ideal for carnivorous plants, too, for you Venus Fly Trap lovers.

The medium contains no harmful pathogens or weed seeds, so you won’t have to worry about the plants starting off and staying well.

Who Should Buy It: This seed-starting soil is a really great choice for anyone growing new carnivorous plants and plants that need some acid in that soil.

Best With Coconut Coir

Burpee Organic Coconut Coir Concentrated Seed Starting Mix
    Coconut coir plant starter mix for easy growing.

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Why We Like It: This product is 100% biodegradable and organic, which makes it a fantastic alternative mix to many options out there. It’s made from harvested coconut husks and works great for all plant types.

It comes in a compact brick that easily expands by adding water and waiting a little while. It’s perfect for starting your seeds, though you’ll likely need to add some composting material to fully sustain the seedlings.

Who Should Buy It: Anyone looking for a moderately easy plant starter mix will find this compact brick of coconut coir a great option. It works for tomatoes, peas, flowers, other fruit, and much more.

Best for Indoors

Window Garden Expanding Organic Fiber Soil
    Fiber soil blend for seedlings.

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Why We Like It: For a fast-growing organic option, the Window Garden seed starter fiber soil is pretty great. It comes in little discs that expand out when water is added and gives the perfect medium for starting wheatgrass, succulents, microgreens, cat grass, and many other house plants.

The natural fibers promote longer life by reducing root rot from overwatering. The fibers open up for proper aeration and drainage, keeping plants healthy for longer.

Who Should Buy It: Folks looking for an easy, non-soil grow base for their seedlings will find this one convenient and easy to use.

What’s in Seed Starting Mix?

There are a few basic components that can be mixed together in different portions to create the right mix for most plants.

  • Compost
  • Perlite or pumice
  • Vermiculite
  • Peat Moss or coconut coir
  • Garden lime (for use with peat moss only)

You can determine what ingredients you need by the type of seeds you’re planting.

Coconut coir or peat moss can be the base ingredient for just about any plant. Peat moss is slightly acidic, though, so you need to make sure there’s some garden lime in there to counter the acid – or use it without for plants that like acid (there are some!).

Perlite or pumice may be used as a soil amendment to help prevent compaction of the soil. These are the little white flecks and spots you notice in the potting soil mixes you purchase. They help the soil drain faster, which is pretty darn important for avoiding root rot.

Vermiculite is a mineral that occurs naturally and is often found in seed mixes because it helps the soil retain moisture so that you don’t need to water the plants as often.

How to Choose the Right Mix for Your Plants

pile of peat moss with herbs in started cups on top of pile
Image credits: Birch Seed Soils via Amazon

Take note: there’s a difference between potting soil and potting mix. Potting mix is always a soilless medium that’s sterile, meaning it’s safer for plants as it doesn’t contain pathogens like diseases and fungus.

Different blends in the mixes will meet the needs of different plans, so as you shop for the right one, consider the types and what they’re good for.

All-Purpose Mix

This type is formulated for indoor and outdoor use for houseplants, hanging baskets, ornamentals, herbs, and edibles. Ideally, if you’re going to grow edibles and herbs, choose an organic mix.

Indoor Potting Mix

before and after of seedling starter mixes
Image credits: Window Garden via Amazon

As the name implies, this blend is specifically formulated for indoor plants. Avoid mixes with compost and bark for best results, as these carry potential fungus and pests.

Coconut Coir

This is best for plants that need to be well aerated as they grow.

Peat Moss

Peat moss is exceptionally sterile, meaning it prevents the growth of bacteria and fungi. It’s also great for drainage, so any plants that are particularly prone to root rot will benefit from a peat moss blend.

Specialty Blends

If you’re planning to grow certain plants like orchids or succulents, you can look for some specialty blends that may cater to their unique needs better than other seed-starting blends.

The Right Ingredients for Your Seeds

bucket of seedling starter mix with trowel and adult hands
Image credits: Burpee via Amazon

Some seeds need different ingredients than others. For example, carnivorous plants like Venus Flytraps, need seed starting mixes with Sphagnum Peat Moss to help them grow healthy. Others are hardier and don’t require special planting mixes. So, be sure to check the recommendations for the seeds you’re planting and make sure the mix matches the needs.

Positive Reviews From Real Users

Though we do our absolute best to review and recommend only the best of the best, there may be something in those reviews that triggers a warning for you for the plants you’re growing. Take the time to scan the reviews from real-life users a bit to ensure there are no red flags for that packet of pumpkin seeds you’ve got waiting to pop into the mix.

How We Picked

The best soil for your seedlings isn’t necessarily the best for someone else’s, so we hunted down the top-rated, best-quality options we could find in a range of types to meet different needs. We looked for the best in each of the main types that folks would need and looked to the contents, the quality of the contents of the mix, the brand and how well-known and well-trusted they are, and, of course, the real-life customer reviews.

Getting Those Seeds Started Right

Whether you’re planting some Drosera capensis as a newbie carnivorous plant grower or getting tomatoes started for your summer salads, you’ll find the right seed starting mix will make all the difference. For most seeds you’ll start this year, the well-trusted brand of Miracle-Gro will do you right. Their Seed Starting Potting Mix in particular is great for your all-purpose plant growing, with many great benefits for your little seedlings, including plant food infused into the mix for super easy care.

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