Testing a 5 component soil mix for herbs

When growing herbs from seeds, I use a 50/50 soil mix of cactus potting soil and regular potting soil. 

I have used this recipe or soil mix for a long time and it works well for all my herbs and vegetables that I start indoors.

But I also do like to test new things. And this article will follow my new project where I plant 8 popular herbs in my new 5 component soil mix.

Growing herbs from seeds is and should always be a labor of love. And I hope the findings over the next 8-12 weeks will give you tips and tricks to use in your own herb garden.

The article will be updated once a week until the seedlings are transplanted into larger pots. When seedlings are transplanted I may post the occasional update but the main focus lies in seeds to seedlings.

Quick Navigation
  1. Setting the parameters for my soil mix test
  2. The herbs we are growing
  3. Start (day 0): Planting the seeds
  4. Week 1 (day 1-7): Waiting for first or seed leaves to appear (cotyledons)
  5. Week 2 (Day 8-14): Will the other 4 pots Germinate and sprout First leaves
  6. Week 3 (Day 15-21): Transplanting, First leaves and true leaves
  7. Week 4 (Day 22-28): Last week before Roundup and conclusions
  8. Week 5 (Day 29-35): Time for summary and conclusions
  9. Summary and conclusion

Setting the parameters for my soil mix test

I have decided to use the following rules to allow anyone to replicate the experiment or use anything we learn.

1. Using the same type of pot

I plant seeds in pots that are a bit bigger than the starter pots I usually use. The pots are made of recyclable plastic and measure 10 centimeters (4 inches) in diameter and are 10 centimeters (4 inches) deep.

2. Using the same soil mix

I am using the same 5 component soil mix for all the herbs.

Peat moss is controversial among gardeners as it is a non-renewable resource and does leave a carbon footprint when harvested from peat bogs. I buy in bulk but when my current storage of peat moss runs out, I will stop using peat moss. Read this article for sustainable and environmentally friendly alternatives.

As this article refers to an actual experiment, the original recipe stays put. My current recipe replaces the 2 parts of peat moss white equal parts of perlite and vermiculite with similar results.

You can read about the exact soil mix recipe in the article about mixing your own soil. But the recipe is basically per below:

  • Standard garden or potting soil (2 parts)
  • Composted cow manure (2 parts)
  • Peat moss (2 parts)
  • Perlite (1 part)
  • Vermiculite (1 part as needed)
Components of the soil mix
Soil & cow manure (dark brown), peat moss (light brown), perlite (white) & vermiculite (grey)

For this experiment, I will be including 1 part vermiculite. 

Garden soil and composted cow manure make up the bulk of the growing medium or soil mix.

Peat moss helps with drainage and also holds moisture and nutrients to be released as the root system will need it.

Peat moss needs to soak to absorb water
Peat moss, dry and water-soaked form

Perlite has many qualities but I mainly use it as it is the master of aeration and helps loosen the soil.

We add Vermiculite as it absorbs water like a sponge and will help control moisture. 

3. Use vermiculite to cover seeds and soil

I will cover the seeds and the soil with a layer of vermiculite. 

Vermiculite will let through some light and help keep the seeds and soil moist and prevent dry outs.

Vermiculite showing when to water
Different colors on dry (left) and wet (right) vermiculite

4. Watering

All pots will be water from underneath using a water bath. 

I will water the pots when the vermiculite shows signs of drying out. It is quite easy to see as there is a change in color.

5. Temperature

I place all pots indoors in the same location with good access to natural sunlight.

The temperature rarely goes below 18 degrees Celsius (65 degrees Fahrenheit).

The herbs we are growing

We are growing the following 8 herbs from seeds. 

Start (day 0): Planting the seeds

I fill the pots with the 5 component soil mix and plant the seeds. 

Basil, oregano, sage and stevia are placed on top of soil and covered with vermiculite. 

Dill, parsley, and cilantro are covered with soil and then vermiculite. Cilantro is planted about 1 centimeter (⅓ inch) deep whereas dill and parsley are simply covered lightly with soil. 

When all seeds are planted pots are placed in a water bath to be watered from underneath. 

When the vermiculite on top absorbs water it starts to change color. Pots are now placed indoors in a spot with good access to natural sunlight and a stable temperature.

I check the pots daily for progress and level of moisture. I water the pots from underneath using a water bath when the vermiculite changes color (lighter in color).

If you look closely at the image you will see 10 pots but only 8 herbs listed. I have planted two pots of parsley and sage. We use a lot in our kitchen and needed to start more plants.

Week 1 (day 1-7): Waiting for first or seed leaves to appear (cotyledons)

4 herbs sprouting first leaves after 1 week
Week 1: Stevia (top left), dill (bottom left) & basil sprouting early first leaves

Now one week has passed since I planted the seeds. I have watered the pots as needed using the vermiculite covering the soil as an indicator to when I was getting close to a dry out.

Already after one week I am seeing first or seed leaves in 4 pots.

Reliable Basil

I was not surprised to see both types of basil (Basil Cinnamon and Basil Opal) germinate quickly.

If I was a betting man those would have been my top two choices.

I will not comment any further at this stage but simply note the the soil mix did deliver successful germination.

But I am surprised to see germination and first leaves already from Dill and Stevia.

Stevia from seeds is always a Challenge

Growing Stevia from seeds can be a roller coaster and the germination rate of the seeds is typically low.

And if you look at the image you will see that there are only 2 first leaves whereas the dill and basil shows a much higher germination rate. This is however expected.

But I am used to stevia needing a least a week before I see any signs of life. I did not expect to see germination and first leaves in 5 days. I have started a new pot using the same soil mix to see if the result can be repeated.

Dill delivering the surprise of the week

I am used to dill germination in 2-3 weeks. I do not find dill to be a difficult herb to grow but it does need its time to germinate and sprout those first leaves.

To see first leaves in 4 days is unusual judging from past experience. I have started a new pots using the exact same mix to see if it can be replicated.

Week 2 (Day 8-14): Will the other 4 pots Germinate and sprout First leaves

It has been an eventful week. And yes, my new pots with stevia and dill has performed just as well as the first set of pots. In both cases I see germination and first leaves within the first week.

There is more to show this week. I will go through the pots and herbs one by one staring with Basil.

True leaves week 2 on both set of basil (opal and cinnamon)
Both basil Opal and Cinnamon with true leaves (week 3)

Basil Cinnamon and Basil Opal

Both pots with basil have continued to grow and thrive. Both pots have seedlings with true leaves.

And as you can see from the image I am guilty of over-sowing (again).

But we make and use a lot of pesto so we do need our basil plants.

Basil Cinnamon is growing faster than basil Opal but this is also expected.

I will transplant the basil seedlings next week. The seedlings will continue to grow and the overcrowding issue will need to be solved.

True leaves on dill seedling (week 3)
Dill seedlings showing true leaves early week 3

Dill seedling with true leaves

The dill seeds germinated fast and the seedling has continued to grow and thrive.

We see true leaves and they have been forming since early this week.

And as reported the control-pot I planted with seeds have also germinated early.

I will transplant the dill seedling next week. This is tricky as dill doesn’t transplant well.

I usually plant dill in large containers or straight in the vegetable garden. But for this test I obviously made an exception. My plan is to transplant the seedlings whole into a larger container.

Cilantro seeds slow to germinate (as Always)

First leaves from coriander seeds
Cilantro is always slow to germinate

Cilantro is one of those herbs that always takes time to germinate.

It is not unusual to wait 2-3 weeks or even longer. And this holds true again.

Mid-week around day 10 I started to see the first leaves pushing through, and now I have 3 emerging seedlings in total.

Learn more here: comparing 3 different methods to germinate coriander seeds here.

It is a bit disappointing to only see 3 seeds germinating so far. I do hope to see more action during week 3.

Oregano seeds slow to germinate
I was expecting oregano to do better after 3 weeks

Oregano looking less than great

Usually oregano seeds germinate in about 10-15 days.

But I can only see one seedling after a full 3 weeks since planting.

It is surprising not to see more seeds germinating.

I have two working theories right now.

Did I add too much vermiculite on top of the soil? As we know oregano seeds want light to help them germinate.

Or maybe the soil mix is simply too rich and fertilized for the small and delicate oregano seed.

It will be interesting to see what happens next week.

Parsley showing promise but no true leaves

Parsley showing first leaves
Parsley showing early growth

I am used to parsley taking up to 4-6 weeks to germinate.

Here, this week I have seen a lot of activity and a surprisingly high germination rate.

I am still only seeing first leaves but the seedlings seem to thrive and develop nicely.

If oregano is the question mark of the week I have to say that parsley is the exclamation point.

Sage showing First leaves

Sage showing first leaves
Was hoping for more sage seeds to germinate after 2 weeks

Sage usually needs about 3 weeks or 21 days to germinate.

Still I am only seeing 1 seedling.

Sage, like oregano, wants sunlight to germinate.

Again, I have to wonder if I have added too much vermiculite blocking the sunlight and hurting the germination.

It is too early to say. But sage seems to follow the same pattern as oregano.

Stevia growing – slowly but surely

Stevia sprouting true leaves
True leaves on stevia seedlings

I only have 2 stevia seedlings after 2 weeks or 14 days. But I do see true leaves now.

I should be pleased with the result. Stevia seeds are hard to germinate.

I am used to stevia seeds needing anything from 7-21 days to germinate. This time around I saw first leaves after 5 days!

Still it would have been nice to see more seedlings developing.

We will have to see what week 3 brings to the table.

Week 3 (Day 15-21): Transplanting, First leaves and true leaves

The week that has passed has rather confirmed the earlier results than produced surprising new developments.

Basil Cinnamon (1) And Basil Opal (2) transplanted

I have transplanted both pots of basil this week into larger pots.

How seedlings have developed after 21 days
How all 8 seedlings have developed (click for larger photo)

Basil cinnamon (1) continued to outgrow Basil Opal (2) but both varieties developed nicely.

As I was dealing with overcrowding, transplanting the seedlings  turned out to be a delicate process.

As you can see in the photo I transplanted some seedlings individually and others in groups of 3-5. 

If you have read some of my other articles you know that I like to deal with overcrowding by thinning out plants as needed. 

I see it as a bonus harvest and enjoy the delicate leaves with tomato and mozzarella or to make another batch of pesto.

Dill (3) Seedlings developing nicely

The dill (3) seedlings have continued to grow and thrive.

Last week I wrote that the plan was to transplant the dill (3) seedling this past week. 

I have however decided to wait one more week. Dill (3) is difficult to transplant and I usually plant the seeds in situ in my garden beds.

The plan is to let the seedlings root in the pot for one more week. I will use the week to harden the seedlings and should be ready to transplant them into a larger container late next week.  

Cilantro (4) sprouting true leaves

I now have true leaves on 2 out of 3 cilantro (4) seedlings. 

It is still a bit disappointing only to see 3 seeds germinating, but I also know that the germination rate can vary.

Let’s see what next week brings.

Oregano (5) still lagging behind

There is still only one oregano (5) seedling. This is not a good result by any standards.

The seed that did germinate sprouted from the very edge of the pot where there was hardly any vermiculite.

Maybe the vermiculite is blocking too much light for the oregano (5) seeds to germinate successfully. 

It is only speculation but whatever the reason the result speaks for itself.

Parsley (6) Sprouting True Leaves

Parsley (6) continues to surprise and is sprouting true leaves on all seedlings – more or less.

I am also seeing a high germination rate suggesting that the seeds like the more nutrition rich growing environment. 

Parsley (6) is still the biggest surprise for me.

Sage (7) Sprouting true leaves

Sage (7) can be tricky to germinate. 

And I guess I am a bit disappointed to only see one seedling so far.

The sage (7) seedling is however developing nicely so that is a positive.

Stevia (8) Both seedlings growing and Thriving

There are 2 stevia (8) seedlings with true leaves coming through nicely. 

It is a good result as stevia seeds are hard to germinate. But not extraordinary. 

Hoping for one more seedling to come in “late”. But time will tell.

Week 4 (Day 22-28): Last week before Roundup and conclusions

Next week I will round up my findings of the first phase of this project.

I almost feel like I could write a summary this week but I want to hold out one more week. This first phase will have covered growing these 8 herbs from seed to seedling that is ready to be transplanted.

Next phase will focus on seedling to plant. I will however only write updates when I have something noteworthy to report.

Basil Cinnamon And Basil Opal Doing well

The transplanted seedlings are doing well and there is really nothing dramatic to report. 

I didn’t lose a single seedling while transplanting the basil plants.

This is however not unusual. I rarely have problems transplanting basil.

Basil cinnamon is still growing faster than Basil Opal. 

Dill Seedlings transplanted today

The dill seedlings are still growing nicely. And I am still pleasantly surprised of how fast the seeds germinated and how well the seedlings are developing.

Healthy dill seedlings
Dill seedlings growing nicely

I have hardened the plant this past week. I started placing the pot outside for a couple of hours. The last couple of days the pot has spent most of the day and night outside.

I transplanted the entire pot into a larger pot today and I do not foresee any problems. 

Dill can be tricky to transplant if you try to separate the individual seedlings.

Instead I simply transplant the whole pot and just make sure to gently rough up the roots to stimulate them spreading in their new growing environment. 

Three Cilantro Seedlings with True Leaves

3 strong coriander seedlings with true leaves
Three coriander seedlings

I now have true leaves on all 3 Cilantro seedlings. 

I am resigned to the fact that only 3 seeds will germinate. 

I have, however, found a new and better way to germinate cilantro seeds.

In a separate project, I concluded that crushing the seeds before planting is a superior way to germinate the seeds. 

Oregano – still disappointing

No more seeds have germinated.

Only one oregano seedling - disappointing
Only one oregano seedling

Oregano likes a light and moist growing environment. 

I have resigned to the fact that the vermiculite did not provide the correct level of moisture. 

Maybe it would have been different if I had covered the pot with plastic or a cheese cloth type fabric. 

And quite possibly is the vermiculite blocking too much sunlight. 

Still all speculations but the result does speak for itself.

Parsley still going strong

The parsley plant is growing nicely and seems to thrive in its growing environment. 

Healthy looking parsley seedlings
Parsley seedlings thriving

The seedlings are doing really well. 

And I am seeing the same result from other pots that I have planted to test the findings. 

It seems like the parsley seeds prefer the 5 component soil mix to my usual 50/50 soil mix of cactus potting soil and regular potting soil. 

I will start using this new 5 component soil mix going forward when I grow parsley from seeds.

Already here I am confident that I have learnt something new.

Sage seedling is doing well 

Only one strong sage seedling
Only one sage seedling

My one sage seedling is doing well. 

It is strange but this has happened to me many times before. 

I plant several seeds but end up with only one seedling.

This one seedling is usually quite strong.

Sure, sage seeds can be difficult to germinate. But still – why does only one seed germinate?

Both Stevia seedlings growing strong

Two strong stevia seedlings
Nice looking stevia seedlings

I now have 2 strong stevia seedlings. 

Both seedlings are developing nicely. And in particular the first seed to germianate that has develope a really nice and strong looking seedling.

I guess I should be pleased with the result.

Still it is nothing extraordinary.

I have seen similar and better results before using my regular 50/50 soil mix.

Week 5 (Day 29-35): Time for summary and conclusions

All pots have now been transplanted and all seedlings have taken to their new larger pots. I have kept the seedlings in pots as it will make it easier to follow them closely over the next couple of months. 

Basil Cinnamon And Basil Opal going strong

The basil plants are doing well and several of the transplanted seedlings have found new homes among friends and family.

Both basil cinnamon and basil opal have grown really well in the new soil mix. 

But to be honest basil is not a difficult seed to work with. I rarely have any problems as long as the soil is kept moist.

My conclusion is that there is no need to use my soil mix for basil.

Basil will grow just as well when I use a more traditional standard potting mix.

On a side note I have found that the basil cinnamon had a tendency to grow a bit leggy compared to basil opal and what I am used to. As I am going back to my original potting soil mix I have not started any test pots to see if it can be replicated.

Dill Seedlings developing nicely

Dill seedling after 5 weeks
Dill week 5

I transplanted the dill seedlings into a larger pot last week.

Dill can be tricky to transplant. But I have had no problems. 

I simply transplanted the whole content of the pot into the larger pot and made sure to place it in the center. 

I expected the dill seeds to germinate in the usual 2-3 weeks. I did not expect to see the first leaves in less than a week. 

I have planted test pots and been able to replicate the success.

Dill is one of the surprises and I will be using a richer soil (or even my 5 component mix) planting dill seeds in the future.

The dill plant is developing nicely and will have its place on the dinner table at our traditional crayfish party later on this month.

Three healthy Cilantro Seedlings

Coriander seedling after 5 weeks
Cilantro seedlings week 5

I ended up with three healthy cilantro seedlings. 

The seeds germinated at different times and there is a noticeable difference in size.

They are all however strong and healthy looking and I expect them to grow into nice and healthy plants.

Again the result was good – much like for basil – but nothing extraordinary.

Given the result I will be using my regular potting mix blend going forward. There is simply no obvious reason to work with custom soil mixes.

I will however be crushing the coriander seeds before planting. Cruising the seeds has improved both germination rate and time. 

Oregano – the only failure

Oregano seedling struggling after 5 weeks
Oregano still struggling

As you can see from the image I have one oregano seedling. 

No more seeds have germinated.

In retrospect I should have covered the pot with plastic film to provide a moist growing environment. 

The belief was that vermiculite would be able to store enough for the seeds to germinate. 

Evidently this was not the case.

I will be using my standard 50/50 potting soil mix going forward.

Parsley developing nicely

Parsley seedling after 5 weeks
Parsley after 5 weeks

The parsley plant is growing nicely and I see no sign of the plant slowing down.

I am used to parsley seeds needing 4-6 weeks to germinate. 

Here I saw the first leaves inside two weeks. 

I have planted test pots and I can replicate the success. 

I will continue using a richer soil like my 5 component mix when planting parsley seeds going forward. 

My one Sage seedling going strong

Sage seedling week 5
Sage seedling after 5 weeks

The verdict is in and I was only able to germinate one seed. 

The one seedling does looks strong and healthy.

But I cannot see anything extraordinary to justify using the 5 component mix.

I have had similar and better results using my standard 50/50 potting soil mix.

And using the 5 component mix does take more time and it is after all a bit more expensive to prepare.

Both Stevia seedlings growing strong

Stevia seedling after 5 weeks
Stevia seedling after 5 weeks

I am neither pleased nor disappointed with the result from the stevia seeds I planted. 

I have 2 strong stevia seedlings. 

Both stevia seedlings are developing nicely and I expect them to grow into strong plants.

But there is again nothing extraordinary with the result.

I will be using my regular potting soil mix when planting stevia seeds in the future.

Summary and conclusion

When planting seeds I use a 50/50 soil mix of cactus potting soil and regular potting soil. 

This is my regular potting soil mix that I use for all seeds.

When I transplant seedlings I use a richer 5 component soil mix.

This whole project was designed to see if germination rate and time would improve using my richer 5 component soil mix from day 1.

Now, for me to use the 5 component mix going forward I would need to see a real and measurable benefit.

After all, it is a lot easier and a bit cheaper to use my regular 50/50 standard soil mix.

Going over the results I have 2 winners, 1 loss and 5 draws.

1 loss – oregano never saw the light of day

I guess enough has already been said but my oregano seeds did not do well.

The conclusion is to use my standard 50/50 potting soil mix and make sure to cover the pot with plastic. 

Once again I am reminded that the oregano seeds need light and moisture to germinate.

5 draws – good but not good enough

Basil cinnamon, basil opal, cilantro, sage, and stevia all showed good results and developed healthy seedlings.

But whereas the results were good they were not extraordinary.

And I feel that I need extraordinary to justify a shift to using my 5 component mix when planting these seeds in the future.

2 winners – great results and a new direction going forward

Both dill and parsley germinated much faster than I expected.

And both have produced strong and healthy looking seedlings and plants.

I have planted test pots using the same soil mix and in both cases I could replicate the results.

I will use a richer soil like my 5 component mix when planting dill and parsley seeds in the future.

Mattias Magnusson: Hello, I'm Mattias, a passionate and experienced gardening enthusiast. I am the creator of MattMagnusson.com, your guide to year-round herb and veggie growing. Let's simplify green living, no matter your space or location.