Our Garden Soil Mix: What We Used, What We Learned, and What We’ll Do Differently
When we decided to expand our garden this year with raised beds and grow bags, one of the first (and biggest!) decisions we had to make was what to fill them with. Pre-bagged raised bed mix adds up fast, especially when you’re filling large spaces, so we opted to create our own DIY soil blend—a mix inspired by the well-known “Mel’s Mix” from Square Foot Gardening.
Spoiler alert: it worked… but not perfectly. Some things grew beautifully, and others gave us a run for our money. Now that we’re well into the season, we wanted to share exactly what we used, what worked well, what didn’t, and what we plan to change next year.
What We Used to Build Our Garden Mix
We followed a loose version of Mel Bartholomew’s “Mel’s Mix,” which calls for:
1/3 compost
1/3 peat moss
1/3 vermiculite
To make it more affordable, we substituted a portion of the compost with topsoil and added straw as bulk filler. Here’s a breakdown of the actual materials we used—everything pictured below, plus vermiculite:
Our Soil Mix Ingredients:
Premier Peat Moss – Adds lightness and water retention
Black Kow Composted Cow Manure – Nutrient-rich compost source
Just Natural Organic Mushroom Compost – Another compost source for variety
Timberline Top Soil – Used as budget-friendly filler
Straw Bale – Added bulk and aeration, inspired by hugelkultur principles
Coarse Vermiculite (not pictured) – Helps retain moisture and promote drainage
We mixed everything together by hand (well… shovels and buckets), layer by layer, right in the beds and bags. It was a workout, but also pretty satisfying!
What Went Well
Let’s start with the good stuff—because we were genuinely happy with a lot of the results.
Plants Grew (Really) Well
Even with a few mix issues, our garden took off. Tomatoes and peppers loved it, our kale and broccoli thrived early on, and flowers like sweet peas and zinnias bloomed beautifully. Overall, the mix created a solid growing environment.
Good Drainage and Moisture Retention
Thanks to the vermiculite and peat moss, the mix held moisture well without getting soggy. This was especially helpful in the heat of summer when our grow bags and raised beds were drying out quickly.
It Was Affordable
Mixing in topsoil and straw let us stretch the more expensive ingredients and cover all of our containers and beds without breaking the bank. That alone made the process feel more doable.
What We Didn’t Love
Now for the honest part—because while it worked, it definitely wasn’t perfect.
The Straw Made the Soil Sink
One of our biggest frustrations was how quickly the soil level dropped. Within just a few weeks of planting, we lost several inches in most beds. We’re pretty sure the straw was the main culprit—breaking down much faster than expected and compacting under watering and root growth.
This left some plants with exposed roots and forced us to go back and top off beds mid-season, which wasn’t ideal.
Topsoil = Too Dense in Some Spots
While the topsoil helped cut costs, it also made parts of the mix feel heavy and dense, especially at the bottom of deeper grow bags. In those areas, root development may have been limited, and we noticed the soil stayed wetter and cooler than it should’ve.
Peat Moss Isn’t Sustainable
Peat moss is a standard in many garden mixes—but as we’ve learned more, we’ve started to feel uneasy using it. Peat is harvested from fragile bog ecosystems, and it takes centuries to regenerate. It’s also a carbon sink, meaning harvesting it releases stored carbon into the atmosphere.
So, while it worked functionally, we want to look for a more environmentally responsible option going forward.
What We’re Thinking About Trying Next Year
This first season taught us so much. Now we’re already dreaming up what we’ll do differently in next year’s garden—and especially how we’ll build the next round of soil mix.
1. Replace Peat Moss with Leaf Mold
Next year, instead of using peat moss—or even coconut coir—we’re planning to start making and using leaf mold. It’s a super sustainable alternative made from decomposed fall leaves, and it adds moisture retention, organic matter, and beneficial microbes to the soil without relying on anything packaged or shipped.
We love that it’s:
Completely renewable
Locally sourced (just use what falls in your yard or neighborhood)
Free
Great for long-term soil health
While leaf mold takes a few months to break down, we’re planning to start piling leaves this fall so we’ll have plenty ready by spring. It feels like a much better fit for our goal of creating a garden that’s not just productive, but also gentle on the earth.
2. Use Less Topsoil, More Compost
We’ll scale back on the topsoil and invest more in compost—either bagged or homemade. Good compost does more for plant health, soil life, and drainage. We may also experiment with composted leaf mold or local bulk compost, if we can find a good source.
3. Try Worm Castings or Compost Tea
For an extra nutrient boost, we’re thinking of incorporating worm castings next season, or even making our own compost tea. It’s a great way to promote microbial life and support plants organically.
4. Use Organic Matter for Base Layers
Instead of straw, we may add twigs, cardboard, or dry leaves at the bottom of deep beds. These materials break down slower, contribute to long-term soil structure, and won’t cause such dramatic settling right away.
5. Add Mulch Around Plants
One thing we didn’t do this year—but wish we had—was mulch around our plants after planting. Next year, we plan to add an organic mulch layer (like wood chips, dried leaves, or straw) on top of the soil around each plant.
Why mulch? Because it:
Retains moisture, especially during hot spells
Suppresses weeds, reducing the need for constant maintenance
Regulates soil temperature, keeping roots happier
Prevents soil compaction and erosion from watering
Improves soil health as it breaks down over time
We think this small step will make a big difference in plant health and reduce how often we need to water, especially in the hotter months.
Final Thoughts
Creating our own garden soil mix was definitely an adventure—and one we’re glad we took. We saved money, learned a lot, and still managed to grow a thriving garden. But like anything in gardening, it’s all about observing, learning, and improving each year.
This season’s mix was a great start, but we’re excited to refine our approach next year. With a more sustainable base, better compost, fewer filler materials that break down too fast, and mulch to protect it all—we think our next round of beds and bags will be even better.
Whether you’re building your first raised bed or just tweaking your container garden setup, we hope this gives you some inspiration—and maybe a few lessons learned the easy way (from us!).
By Leah Ann Grace
