You can never have enough potting soil and a good potting soil recipe is an absolute must. You can’t fool around and get a potting soil recipe wrong because a 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
Sand and gravel are special because they drain quickly and drainage is the key to success, especially when it comes to ornamental plants in a landscape. 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.
The Big Topsoil Rip Off
When you buy topsoil it is important to 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 that is not good topsoil. It looks great in the pile, but the minute it gets wet it turns to soup, then mud and then packs hard as concrete. Good topsoil doesn’t need to be shredded. When you squeeze good topsoil in your hand it will not stick together like a softball.
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 to mix the organic matter with the existing soil. Leaf compost works great and just about any compost in general works well with the only exception being peat moss which is still okay. Peat moss holds moisture so it’s okay in sand and gravel soils, but not in sticky soil like clay. Another thing to understand is that peat moss contains no nutritional value whatsoever so in most situations I consider it a waste of money.
The best thing to do for your soil is 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 improves the soil.
The Magic Word
Bark can work magic. Trees are made up of two things: bark and wood. Wood is good for building houses and roasting marshmallows and bark is good for growing plants. Bark is not good for building houses that’s why it is removed from the logs before they are cut into boards, but wood is not 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. 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!
My 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, in fact 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 in this article, the magic to a good potting soil recipe is this; it must drain really well and it has to be light and fluffy.
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! And 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 you are growing plants in nursery containers. If you let those wood chips rot for a really long time, three to five years, they 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 rotted 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.
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 known 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 its 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. I do 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 then 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 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. Check to see ow wet the soil in the bottom of the container is. 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 will have 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, a combination of 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 a potting mix of just bark mulch? They do, but they also 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.
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!
Mike McGroarty is the owner of McGroarty Enterprises and the author of several books. You can visit his website at Freeplants.com and read his blog at Mikesbackyardnursery.com.
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