Potting Soil vs Seed Starting Mix
If you’re new to gardening, or new to planting your own seeds instead of using purchased seedlings, you may be wondering what the difference is between potting soil and seed starting mix. Why does seed starting mix usually cost more? Is seed starting mix really necessary or worth it? And why can’t you just grab a handful of dirt out of your yard to plant your seeds in?
Potting soil and seed starting mix are two different types of soils that serve two different purposes. Discover the differences between potting soil and seed mix and how to use them correctly.
Whether you are growing a big garden or a small indoor plant, gardening becomes easier when you know the differences between potting soil and seed starting mix.
Here are the basic differences between potting soil and seed starting mix:
|Potting Soil||Seed Starter Mix|
|Main Purpose||to transplant plants or grow container plants||to help seeds germinate into seedlings|
|Typical Ingredients||field soil, compost, composted manure, sand, fertilizer, moisture retention granules, perlite, peat moss, vermiculite||coconut coir fiber, sphagnum moss, perlite, peat moss, vermiculite, diatomaceous earth|
|Texture||coarse and dense||fine and loose|
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Table of Contents
The Difference Between Potting Soil and Seed Starting Mix
The differences between potting soil and seed starting mix begin with their ingredients.
Seed starter mix has a fine and light texture and has the purpose of allowing seeds to germinate easily and healthily.
Potting soil is heavier, denser, and coarser, making it ideal for plants that are undergoing transplanting or container growing. (It’s important to note that potting soil is still far less dense than most yard dirt, though.) Both are important at different times of the plants’ growth stages. Do you have some leftover potting soil from last year? Learn how to tell if potting soil is still safe to use.
Many seed mixes are inert and do not contain nutrients. This is great for germinating seeds that don’t need added nutrients, and may even be harmed by them. Although exact recommendations vary, most experts recommend holding off on fertilizing seedlings until they’re 3″ tall or have a couple sets of true leaves whichever comes first (source). After that, dilute your fertilizer carefully according to the package instructions to avoid burning your delicate seedlings.
I personally use Foxfarms nutrients diluted according instructions for seedlings when I need to fertilize my young plants. The eggplant seedlings below are definitely large enough to need fertilizing:
The lack of nutrients is perfect for tiny seedlings, but harmful to growing plants that need added nutrients. That’s why you need to transplant into potting mix once the seedling is ready to make the move.
Both potting soil and seed starting mix tend to be technically soilless. Seed starting mix isn’t even always a mixture of ingredients – plain coconut coir can be used as an eco-friendly, completely renewable seed starting medium.
Is Seed Starter Mix Necessary?
Do you really need a seed starter mix for your seeds? The straight answer is no. However, seed starter mixes are highly recommended!
Some may think if the seed starter mix is only used for the first short stage of a plant’s life, it’s not necessary. This can be a costly mistake.
Seed starter mixes give the seeds optimal conditions to begin their journey in life and increase the chances of successful germination.
The primary benefit of seed starting mix (in my opinion) is that it reduces the likelihood of damping off. Because damping off is caused by fungi and fungi-like organisms, it’s more common in humid climates.
If damping off strikes your seedlings, it can ruin your entire planting season. Even if your seedlings survive, they won’t be as strong or vigorous as truly healthy seedlings. If a longer season crop, like squash or tomatoes, are affected, you may not have time to start a second batch of seedlings and have the plants fruit successfully before the weather becomes too cold in the fall.
What to look for (and avoid) in seed starting mix
I’m personally a believer in organic gardening, so I try to find organic potting soils and seed starting mixes whenever possible. If this is your personal preference, too, select an organic seed starting mix.
I used miracle grow. now what?
So I used miracle grow as my growing medium. After doing research I realized it's the worst. I am already into week three with my seedlings (2.5 inches tall) and am finding this out now. I'm thinking its too early to transfer them to proper soil, so my question is, what should I do? Are my plants fucked? There is so much info online that says not to use miracle grow, but nothing on what to do if you started using it already.
The package just says miracle grow potting mix: 0.21-0.11-0.16 On the back it says: Total Nitrogen:0.21% Available phosphate: 0.11%% Soluble potash: 0.16% Organic matter: 30% Maximum moisture: 70%
I know I should have done more research before hand to avoid this. I just found a bunch of old seeds a few weeks ago and germinated them on a whim, and then started researching after I had put them in soil.
I am using an old 150W HPS light I bought around 10 years ago. I had done one semi successful grow with it back then.
I am doing 12/12 from seed, which in retrospect I would not have done, but at the time I was just looking for the simplest method possible.