Raised Beds and Potting Soil. The Recipe is the Magic that makes for Beautiful Plants!
A good potting soil recipe and a good building building recipe are interchangeable. A good potting soil recipe is an absolute must. You can’t fool around and get a potting soil recipe wrong. I poor potting soil recipe will stall, if not completely kill the plants that you are attempting to grow in it.
Poor Soil is Poor Soil.
Plants growing in a raised bed are more forgiving, but still, poor soil is poor soil and plants always suffer in poor soil. Now, if you have soil in your yard that is well drained, meaning that when watered heavily the water drains right through the soil in just a few hours, you really don’t have to build raised beds.
Sand and Gravel Soils are a Blessing to have in Your Yard.
What’s so special about sand and gravel? Drainage baby! Drainage is the key to gardening success, especially when it comes to ornamental plants in a landscape. That’s why you see so many nurseries here in Madison and Perry, Ohio. We are right on the south shore or Lake Erie and a few million years ago the glaciers left us with some awesome soil for growing nursery stock. Not all of Perry and Madison have fantastic soil. These are really two very small communities and even then the soil near the lake is very different than the soil just a few miles south.
That’s why we have so many nurseries adjacent to one another. If the soil is good, you find nursery plants growing by the tens of thousands around here.
Amending Sand and Gravel Soils to make Your Plants thrive.
But First, Mike Comes Clean.
Before I babble off about amending sand and gravel soil I have to come clean and tell you that I don’t think I’ve ever done it myself. When Pam and I lived over on Middle Ridge here in Perry our soil was pure sand and gravel. Mostly gravel. Not even close to being nice and dark like good organic soil is. When I landscaped the house I bought some soil to raise the beds from a friend of mine who had a big pile of, you guessed it, more sand and gravel.
When I dug out the beds for my Backyard Nursery I rented a tractor and just made big piles of soil (sand and gravel) then later I took my little rototiller and groomed the top of the piles to make them rounded mounds instead of just big piles of sand and gravel. Then I landscaped them.
Stick with Me. This is Educational.
That’s right, I planted beautiful trees and shrubs, numerous Japanese maples, Junipers, you name it, in soil that most consider too poor to grow a thing. Same thing around the house. The soil I put in those beds was nothing but sand and gravel.
Mike’s Big Confession!
Not only did I plant all of that stuff in sand and gravel, but I never fertilized them! Not one time. I never fertilize the plants in my landscape. Except maybe roses. I just don’t believe in it. Take a Look at these Photos and Tell Me Whether or Not these Plants are Suffering in that Poor Soil.
When Growing Plants for any Purpose, Drainage is Everything.
If you are landscaping your house, or building a raised bed in the middle of the yard for a landscape planting, the soil doesn’t have to be perfect, but it should at least drain well. Good topsoil is great for raised beds, but not pots. Definitely don’t use topsoil in a container. More about that in a bit.
The Big Topsoil Rip Off!
When you buy topsoil it’s important that you buy good topsoil. Today there are too many soil dealers that are taking really heavy, sticky clay soil, running it through a soil shredder and selling as good topsoil. And it’s not good topsoil. It looks great in the pile, but the minute it gets wet it turns to soup, then mud then packs hard as concrete. Good topsoil doesn’t need to be shredded. Good topsoil when you squeeze it in your hand will not stick together like a softball. I made a really short movie about topsoil. Have a watch.
Man oh man did I get off track. Get me talking about dirt and I get all giddy like a school girl!
Back to Amending Soil.
If you have sand and gravel soil and would like to amend it, that’s easy to do. Just work in some kind or many kinds of organic matter and till the bed mixing the organic matter with the soil that you have. Leaf compost works great, just about any compost works great, peat moss is okay. Peat moss holds moisture so it’s okay in sand and gravel soils, but not in sticky soil. But peat moss contains no nutritional value whatsoever so most of the time I consider it a waste of money.
The Best Thing to Do for Your Soil?
Just plant in the soil that you have and then apply about two inches of good bark mulch after you are done planting. The bark mulch does a great job of controlling weeds and eventually breaks down and actually improves the soil. Around here we have shredded hardwood bark mulch readily available, some areas have pine bark mulch, out west they have fir and hemlock bark mulch.
What’s the Magic Word?
Bark! Trees are made up of two things. Bark and wood. Wood is good for building houses and roasting weenies and marshmallows. Bark is good for growing plants. Bark is not good for building houses that’s why they remove it from the logs before they cut them into boards. Wood is not good for growing plants. Not all good for growing plants!
What’s the Big Deception in the Mulch Business?
Grind up wood (pallets) dye it a pretty color, usually brown, red or black and sell it as mulch. As a mulch, to keep down weeds etc. this ground up pallet wood isn’t a terrible thing, but it’s not my thing. I like bark mulch. For growing plants, mixing in beds or in potting soil, you have to use bark mulch! You cannot use wood mulch for growing plants. No, no, no! Do not put wood mulch in your potting mix! Guess what? I made a movie about mulch, it’s informative. Take a peek.
Mike McGroarty’s Secret Potting Soil Recipe.
There are only two things that I know how to make that are worth talking about. Dirt Farmer Fudge and potting soil. My fudge is awesome, but my potting soil is better. My potting soil rocks!
My potting soil recipe is actually pretty simple. I start with a pile of bark mulch. You can use hardwood bark mulch, hemlock or fir bark mulch, pine bark mulch and probably even rice hulls, but I don’t have personal experience with rice hulls. Based on what you’ve learned so far on this page the magic to a good potting soil recipe is this. It must drain really well and it has to be light and fluffy. Here is a video I made to show you how I do it!
Plants Breath through Their Roots!
Plants absolutely, positively must be able to transfer oxygen through the soil to and from their root system. That won’t happen if they are planted in wet ground, or in a potting soil that does not drain well. That’s why the potting soil must be light and fluffy, it has to be porous enough that the oxygen can pass through the potting soil. I know it sounds crazy because if roots are exposed to air they die, but still the soil has to be able to breath. That’s easily accomplished if you use a potting soil that is that is 85 to 90 percent bark mulch.
Bark Mulch! Not Pretend Wood (ground up pallet) Mulch.
Not Wood Chips from a Tree Service!
I know, I know I know. It’s tempting to use those free wood chips from the tree companies. Can’t beat free! Except when growing plants in nursery containers. If you you let those wood chips rot for a really long time, three to five years, they might work. Might work! They’ll be good for something in the yard, but I don’t know that I’d ever put them in my potting soil mix unless they were completely rooted down to pure compost.
But keep in mind, pure compost is usually too fine and often too sticky to use as a potting mix. Compost adds nutrition to bark mulch for a potting mix, but I wouldn’t use more than 10 or 15 percent of compost in my potting mix. What I do is stock pile hardwood bark mulch so I always have some that is decomposing. The more decomposed bark mulch is, the more nutritious it is. But you have to be careful because the more decomposed it is the more likely it is to hold too much moisture for a potting mix.
Right now at the end of March I have a big pile of bark mulch that I’ve been collecting and adding to for about two years now. In about a week I’ll order in another 15 yards of fresh bark mulch and have it dumped right next to the pile of older material that I have. I’ll mix some of the fresh mulch with the mulch that I’ve had for a year or two. I want about 10% of the fresh mulch in the mix to make sure I’ve have good aeration in the mix.
Do Not Add Sand to Your Potting Soil Mix!
This is contrary to what others will tell you and it’s probably contrary to what I might have told you a couple of years ago. I’ve never used a lot of sand in my mix, but at one time I did add some sand to my potting soil. About two years ago I was talking to a very experienced, very knowledgeable grower that I’ve know for about 40 years and he told me that he no longer uses any sand in his potting soil. As he explained it, and it made perfect sense when I heard it, is that the sand works it’s way into the pours of the potting soil and pretty much eliminates the veins needed for the transfer of oxygen. The sand actually impedes drainage and the flow of oxygen to the roots of the plants.
Should You Add Small Stones to Your Potting Soil Mix?
You can. If your soil is not draining well enough you can add pea gravel or silica stone to your mix. The stones should be tiny, less than 1/4″ in size and they should be neutral to the soil. In other words, don’t add something that will break down and alter the ph of your potting soil. At this time my plan is to not use any stone in my potting mix unless I run into a drainage problem.
Testing Your Potting Soil for Drainage.
The easiest way to see how well your potting soil drains is to fill a nursery container with potting soil and lots of water and watch to see if the water runs out or stands on top of the potting soil. Don’t fill the container all the way to the top with potting soil, leave about an inch or so so you can see how fast the soil drains.
If you have plants potted up you can check them as well. Water them really well, wait about four hours, then go out and take a container, plant and all and turn it upside down and slip the pot off. How wet is the soil in the bottom of the container. It should be moist but not soggy, soaking wet. Check your plants right before you are to water again. In most cases you only need to water once a day so if you check right before you water it’s been about 24 hours since you last watered. The root zone of the plants should be cool and moist but not wet.
My Potting Soil Recipe in a Nutshell?
Bark mulch. Both really decomposed and fresh bark mulch. When I say fresh bark mulch I don’t mean that mulch that just came off the tree. Most of the bark mulch that you buy has been piled up in the saw mill for some time so by the time we buy it’s not really fresh. It’s just fresher than what I have in my existing pile.
Do Plants Really Do Well in Potting Mix of Just Bark Mulch?
They do, but they need supplemental fertilizers. A good potting mix contains some nutrition, but it won’t last long. We apply a slow release fertilizer as soon as we pot up our plants. I go into detail about this inside The Backyard Grower’s University.
Can You Use Topsoil in a Potting Mix?
No, no, no!!!! Container grown plants are always grown in a “soil less” potting mix. Topsoil will never drain good enough to be used in a potting mix. Putting potting soil in your potting mix is a huge mistake and your plants will hate you for it!
Okay, that’s it. Gotta run! I have a hot date with two donkeys. If you have questions or comments post them below and I’ll chat you up.