Can I start seeds in regular garden soil?

Yes, but your results will vary – and there are much better ways to start seeds.

Today, you will learn how you can make your own quality garden or potting soil for seeds, seedlings and plants using regular soil. 

We will focus on understanding the importance of soil structure, drainage, nutrition and how the size of your chosen container or grow bag can make or break you.

Or, if you prefer, at least you will know what to look for when you buy your next bag of potting soil.

Soil can get expensive – very fast

We know that soil can get expensive. Especially when growing larger plants like tomatoes and peppers in containers or grow bags.

And, depending on your budget, you can look at it in 3 different ways:

1. Deluxe: Using specialty soils to start seeds and grow plants

In a perfect world, you will start your seeds in a seed starting mix, develop your seedlings in specialty potting soil mixes and then grow your plants in a specialty herb or vegetable garden soil.

But it can get expensive. And while it is great to grow and eat home grown herbs and garden vegetables, you also want to save some money in the process.

2. Budget: Start seeds in the garden soil that is available

This is the cheapest and often fastest way to get started. And it is better to start with regular garden soil than not start at all for yet another season.

There are several reasons why regular garden soil is not ideal including the risk of existing soil-borne pathogens and diseases, (too) high levels of fertilisers and the soil being too compact and heavy.

Still, I encourage you to get started with the soil and budget that is available to you. Check out this article to get started today: How to start growing vegetables at home (10 steps).

3. Our preferred way: Construct your own soil mixes

We use the word construct as it is really all about using 3 – 4 quite basic ingredients and mixing them to fit your purpose.

It is economical but will require a bit of effort on your part. But when you understand how to construct your soil, you are literally set for life.

A DIY experiment to understand potting and garden soil

1. Start by buying one small bag of top shelf high quality potting mix and one bag of regular garden or potting soil. 
2. Make sure you are comfortable with the cost of the regular garden or potting soil you choose. After all, this is the soil you will be working with in the future.
3. Next, open them side by side and look, smell and feel the difference of the soils. Focus on texture and feel.
4. Now, take 4 identical pots. Fill 2 pots with the quality potting soil mix and the other 2 pots with the regular garden or potting soil. 
5. Now, top water two of the pots and bottom water the other two pots. Observe the difference in how the soils drain and retain moisture. Make sure you also use your hands to feel the difference.

It sounds simplistic, but you will learn a lot from watching and feeling the soil – both before and after watering.

Next read the packaging to find out what the soils are made from. When you know, it will be so much easier to either mix your soil from scratch or improve the less expensive regular garden or potting soil to mimic the attributes of the more expensive potting mix.

How I mix my potting soil mixes

Reading the back of a soil bag can give anyone a headache. Many of the ingredients tend to be unknown to me.

I use regular potting soil as a base for starting seeds and regular garden soil as a base for my plants in containers and grow bags. And I use 3 amendments to change the structure, drainage and level of nutrition of my soils to fit the specific purpose at hand.

• perlite – improves aeration and drainage
• compost – adds organic matter, nutrition, and structure
• peat moss (wooden chips, coconut coir) – sterile (disease resistant), aerates the soil, retains moisture, and does not compact

Peat moss is somewhat controversial among gardeners as it literally takes thousands of years [1] to form and as such has to be considered a non-renewable resource. I buy in bulk but when my peat moss runs out, I will stop using peat moss for other sutainable and more environmetally friendly alternatives. 

Starting seeds: I start most seeds in the regular potting soil mixed with 5-30% perlite to make sure the soil drains well. I purchase perlite in 100 litre sacks from a local garden specialist. 

I use more Perlite for Mediterranean herbs like sage, rosemary, thyme, tarragon and oregano. Other herbs like for example common basil and Thai basil get less perlite. 

And then there are the exceptions like dill and parsley where I use a 5 component soil mix for starting seeds.

Growing seedlings and plants: We grow seedlings and plants in a mix of regular garden soil (30), aged compost (30), peat moss (30) and perlite (10). 

The aged compost adds nutrition and structure, Perlite helps with drainage and overall aeration whereas peat moss retains moisture, helps with aeration and adds structure to the soil.

Understanding why and how

If you have read our articles you know that we measure pH levels and mix our own potting soil mixes. And we do this because gardening is a passion, and we have spent a lot of time (and money) on tools, equipment, and educational programs.

But we also mix our own soils and make our own DIY grow bags because it saves us money. 

And we did not start gardening using pH level meters and full spectrum grow lights.

So our advice to you is to always try to understand why and how. Let’s use specialty soil mixes for Mediterranean herbs as our first example.

Save money mixing your specialty soil for Mediterranean herbs

If you only learn one thing about Mediterranean herbs, you should be aware that they do not tolerate wet soil. Rosemary, oregano, sage, thyme, and tarragon may tolerate poor soil – but not if it is wet. 

And when we look at the why, it is not hard to understand why Mediterranean herbs growing in hot Mediterranean landscapes prefer dry to soaking wet soil. 

Taking it one step further, it is plain to see that we would need soil that drains well. 

If we start with standard or regular garden soil, we could add Perlite and go easy on the compost and peat moss. So when we construct our soil it goes something like this:

• Tolerates poor soil: Increase garden soil from 30 to 60, and decrease compost from 30 to 10.
• Does not tolerate wet soil: Increase Perlite from 10 to 30. No peat moss as it is very effective in retaining moisture.

By understanding why and how we have made our own specialty garden soil for Mediterranean herbs that are less fertile and that drains really well. 

Now, let’s look at a vegetable that most home gardeners love to grow, tomatoes. 

Growing tomatoes successfully in cheap soil

We grow several different types of tomatoes every season.

Start cherry tomatoes from seeds in lean potting soil mixed with perlite. The potting soil mix drains well while holding enough moisture for the seeds to germinate.

Beefsteak tomatoes are also started from seed in a lean potting mix with added perlite. 

But as the beefsteak tomato is a larger plant and needs more soil, we add more perlite as the plant grows, develops and is transplanted into a larger container or grow bag. 

There are also many – often more expensive – soil-less potting mixes. 

We have, however, never had problems germinating tomato seeds in the less expensive soil-based potting soil mixes. And here is why. 

We cover pots, use a spray bottle to mist the soil and always make sure the potting soil mix drains really well. If there is a lot of condensation on the inside of the cover or plastic, we dry it off. 

And we are cautious if we water starter pots. We avoid top watering and ensure the pots are allowed to drain properly if bottom watering. Because overwatering is your biggest enemy when trying to germinate tomato seeds.

For our tomato seeds, we use regular potting soil mixed with 20% Perlite to make sure the soil drains well.

Soil less potting soil mixes are not necessarily “better”. But, yes, they are often more forgiving if you are prone to over watering as they drain well while still retaining sufficient levels of moisture. 

5 gardening tips or principles to live by 

I have learned a lot from my parents. They were gardeners when it was more normal than an exception to rely on the herbs and garden vegetables you grew in your garden. 

And we always had fresh vegetables. And I know they used one and the same soil for all things they grew. But they were masters at continuously improving the soil with compost, mulch, and aged manure from the local farmer.

From my parents, I took this desire to simplify and look for common denominators. To try to understand the how and why.

After all, there has to be a better way than to buy soil for tomatoes, soil for hot peppers, soil for Mediterranean herbs, soil for garden vegetables, etc.

Here are 5 tips or principles that I live by and serve me well. 

1. Seeds do not need fertilizer to germinate

You have most likely seen people germinate seeds on moist paper towels. 

This in itself tells you that there is no need for extra nutrition or fertilizer for seeds to germinate. Quite the contrary, fertilized soil may burn the new delicate roots as they sprout.

Think lean potting soil mixes that drain well.

2. Seeds need moist but not wet soil

Your seeds will rot and die if they are sat in wet soil. The same goes for the roots of your seedlings and plants. Watch out for leaves going brown or yellowing, as this is often a first sign of overwatering.

Our best tip is to mist your starter pots with a spray bottle and then cover them with plastic.

Top watering starter pots is difficult – it is so easy to overwater.

3. Look at your seeds before you plant

Do not treat all seeds the same way. Seeds can be grouped in different ways. Here are 6 ways to group seeds. 

Big seeds are generally speaking more sturdy than smaller seeds and need to be planted deeper. Check the seed packet or use my general rule 

1. Big seeds are planted ca 3 cm / 1 inch deep
2. Small seeds are planted ca 1 cm / ½ inch deep

Expensive seeds, rare seeds, or seeds that are difficult to germinate need to be treated more delicately than inexpensive, common, and easy-to-germinate seeds. 

For example, I never use heat mats when starting basil seeds. It is just not necessary. But I always use heat mats or other methods to control the temperature when I start hot peppers like habaneros or Bhut Jolokia ghost peppers. 

Harvested seeds and old seeds left over from last season are always pregerminated as it is challenging to know what germination rate to expect. 

4. Construct your soils (texture, drainage, nutrition)

You can save a lot of money by making or constructing your soil mixes. Buying in bulk will mean spending a bit more initially, but it will save you money in the long run.

Start with your base potting or garden soil, and then add perlite, vermiculite, and compost to get the texture, drainage, and level of nutrition you need. 

Also, remember that not all plants need fertile soil to grow. Oregano is an example of a plant that will accept lower soil quality as long as it drains well. 

6. Size of the container and why bigger is not always better 

Do not use big containers or grow bags for all plants by default. And here is why.

Larger containers need more soil. Growing smaller plants in containers with too much soil means that the top layers of the soil will dry out faster than the bottom layers of soil.

You will have a situation where the soil is dry at the top while wet at the bottom.

And when you water again, you will add moisture to the already wet soil at the bottom of the container.

This is when you risk drowning your roots, causing yellowing leaves, root rot, and a dead plant. 

Bonus tip: Are your pots or containers sitting in rainwater?

Placing pots and containers on a wooden deck can cause marks and water damage. To protect the surface, it is customary to place the pots on saucers or trays. 

Using saucers can also create a protective layer if you place your containers directly on the ground. 

But always remember to check for water sitting on the saucer. The saucer will collect water as it drains through the pot, and you could end up with pots sat in constant wet and yellow leaves.

Pay special attention to water levels in periods of rainfall. 

Summary and conclusion:

Quality soil is vital to being successful in growing herbs and garden vegetables. 

But quality soil does not have to be expensive. And when you understand what makes quality soil work, you can construct or mix your quality soil. 

I am sure there are commercial companies with research and development departments that create quality soils that are pretty much impossible to replicate. 

Still, from my experience, the soil you can create yourself will cost a lot less and will yield fantastic results.

Focus on soil structure, drainage, nutrition, and the size of your chosen container or grow bag. Get these 4 things right, and you are on your way to great things. 

Do not be afraid to experiment. Do something slightly different with one pot, observe the results, learn new things, and move on.

I grow a lot of habanero peppers. And last year, I had one pot that I watered less than my other plants. And this plant yielded more fruits and a hotter and tastier pepper than I was used to. 

In other words, never stop testing and learning. 

[1] https://site.extension.uga.edu/fultonag/2021/06/a-case-against-peat/