Seed starting in containers, whether indoors or outdoors, is a very popular and common gardening practice, but it also comes with a lot of questions. It is tempting for people to assume that topsoil should be used for seed starting. However, read on, as this may not be the case.
So, can topsoil be used to start seeds? No, it is not recommended to use topsoil for starting seeds in containers. Seeds need the right amount of oxygen and moisture for the best chance of germination, and topsoil does not provide the best growing medium that suits these needs.
It is an odd paradox that the best soil for seed starting actually contains no soil at all! I can definitely see how it can be confusing that topsoil should not be used to start seeds, even though plants and seeds grow outdoors in the soil in nature all the time.
What’s Wrong With Topsoil for Seed Starting?
In order to understand why topsoil does not make the best growing medium for seed starting, let’s first get an understanding of what qualities seeds need in order to germinate and grow in the best way possible.
Basic Soil Needs for Seed Starting
- Air. Once a seed germinates, the roots of the plant need oxygen in order to grow. This is a basic need of all plants and is especially important for a young plant trying to establish its roots.
- Water. Seeds need moisture in order to germinate. The growing medium should have good enough drainage so that once the seed sprouts, the roots are not drowning. It also needs to be able to hold water well – like a sponge – in order to provide enough moisture for those roots.
- Space for easy growth. Once a seed sprouts, the roots need a nice loose mixture to be able to easily grow. The roots need to be able to spread easily. Too much compaction would prohibit this root growth.
- Freedom from predators. Just like an infant baby, seedlings are not very strong and will do best if you provide them with the best environment possible. Having the growing medium be free of disease, insects and mold will give seedlings a better chance to grow healthy and strong.
Topsoil Misses the Cut
Even if topsoil from the garden is top notch, it can still cause issues when putting it into containers; especially, if starting seeds indoors.
- Topsoil is too heavy and compact. This causes issues with the first three needs for seed starting listed above. Heavy and compact soil does not drain well and water can choke out your plants. At the same time, it does not provide enough air flow to the roots and the roots cannot push through the heavy and compact soil easily enough to grow and flourish.
- Topsoil can contain diseases. Too many pathogens and disease organisms are out there that can harm seedlings at their early stage of life when they are not strong enough to fight off these issues.
- Topsoil can contain harmful insects. If topsoil is dug up out of a garden and brought inside to start seeds, it will undoubtedly have some insects in it as well. While this may upset a spouse, it can also be a killer for seedlings if those insects like to feed on roots or young leaves.
As you can see, while it may be tempting to use soil from the garden to start seeds in containers, it is best to find a soil-less mix for any seed starting needs. Continue reading to find out what type of mixes are recommended for seed starting.
What Is the Best Seed Starting Mix?
Well, if topsoil should not be used to start seeds, what is the best choice? As listed above, certain qualities are necessary for a seed starting mix to have in order to give plants the best chance for success.
Seed starting mixes generally consist of peat moss or coco coir, vermiculite and perlite. Peat moss or coco coir is a great choice for the base of the mix because it is an organic material that holds water well while providing many channels for air. Vermiculite and perlite are lightweight minerals that improve air circulation and drainage when used in a soil mix.
Seed starting mixes can be bought at the store. It can be confusing as to which product to buy because unfortunately, companies are not always very consistent with their labeling. Some products labeled as potting mix would work perfectly fine for seed starting, while others would not. Other names used are potting soil, container mix, and seed starting mix. In general, look for the terms seed starting or germinating and you should be good to go.
Keep in mind that seed starting mix does not need to contain fertilizer. After germination, a seedling gets all the nutrients it needs from the original seed from which it sprouted. Adding fertilizer, especially synthetic types, can actually do more harm than good to seedlings. They are too powerful and can burn your plants. For more information on fertilizer for containers, check out this article – Does Potting Soil Need Fertilizer?
For no one can lay any foundation other than the one already laid, which is Jesus Christ.1 Corinthians 3:11
Make your own mix!
To save money, I buy peat moss, vermiculite and perlite in bulk and make my own mix. If you search on the internet for homemade seed starting and potting mixes, you will undoubtedly find at least ten different recipes. I think they all probably work just fine, so do not get too hung up on the amounts of each item.
I use a bowl from the kitchen and combine four parts peat moss, one part vermiculite and one part perlite. Since I use the same mix as my potting mix, I also add one part of my homemade compost I make from shredded leaves and coffee grounds and one part of my homemade worm castings.
Remember, seedlings do not need this extra fertilizer, but because these amendments are organic, it will not hurt the plant in any way. They will start taking up the nutrients from the compost and worm castings when they need it.
When mixing these ingredients together, be sure to water it well before using it in any containers. If you grab a handful of the mix and squeeze, a few drops of water coming out is the correct amount of moisture.
If you want more details about making your own seed starting mix, check out our full article DIY Potting Soil and Seed Starting Mix to Save Money.
What is the Purpose of Topsoil?
You may be wondering that if topsoil cannot be used for seed starting, what are ways it can be put to good use? You are likely able to obtain it for free or buy it at the store very cheap. The following are a few ways topsoil can be put to good use.
- Use it to fill raised gardening beds. Other amendments should also be mixed with it, such as compost, but good topsoil does contain a good amount of good minerals and nutrients that plants will love.
- Use it to amend poor soil. Again, other amendments should also be mixed with it. While topsoil does contain some nutrients and minerals, it is quite heavy and can compact easily, so other organic material needs to be added for additional nutrients and better drainage.
- Use it in the lawn to fill in bare and low spots. Spread the topsoil and then apply grass seed.
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How is topsoil formed? Topsoil is formed slowly over time from the breakdown of minerals in rocks and decaying matter from dead plants. It is claimed to take one hundred years to form one inch of topsoil!
Can you use topsoil instead of potting soil? In general, this is not recommended because topsoil is too heavy and can compact easily in containers. Check out our article Can You Use Garden Soil for Potted Plants for more information.
What is the difference between garden soil and topsoil? While these terms are commonly interchanged and can mean the same thing, technically speaking, topsoil is the natural soil that would be removed from the top few inches of untouched ground, while garden soil is topsoil that has been amended with compost or other organic material.