FARGO -- I'm sure my grandparents never heard of Miracle-Gro. To them, "miracle grow" meant their gardens survived the drought and grasshoppers of the 1930s and yielded enough food to store through winter. Besides large survival gardens, geraniums and other houseplants were a must in sunny south windows. And Grandma's green thumb didn't depend on home improvement mega-stores for packaged potting mixes, Miracle-Gro or otherwise.
Where did they get their potting soil? As a boy, I helped Mom haul galvanized washtubs full of "good, black dirt" from the shelterbelt where decades of fallen leaves had decomposed into a rich, black compost. Old gardening books promoted home-blended potting mixes of equal parts soil, sand and well-rotted manure. I like today's mixes better, because even the best outdoor soil eventually became hard-packed in a pot.
In our weekly visits, I've often mentioned the importance of a high-quality potting mix. Does it really matter what mix you use, or are they pretty much the same? Let's go shopping.
Notice that some brands are labeled potting mix and some are labeled potting soil. "Soil" has a broad definition, and the terms potting soil and potting mix are being used interchangeably. Few contain actual dirt-type soil. The better quality products I've found are labeled potting mixes. Apparently no state or federal regulations govern quality of potting products, although the label must list ingredients in decreasing order of volume.
Today's "soil-less" mixes contain one or more of the following. Sphagnum peat moss absorbs and holds water. Vermiculite is the golden, flake-like material that holds air, water and nutrients. Perlite is the white, crunchy bead-like component added for aeration. Forest products like ground bark increase moisture retention but can limit air. Larger bark particles increase aeration.
A good potting mix must strike a balance of being porous enough for drainage and root aeration while retaining the right amount of water and nutrients. The mix shouldn't become hard-compacted over time.
How do commonly available brands of potting mix compare? I purchased seven types from home improvement stores, mass merchandising marts, and locally owned garden centers.
The ultimate deciding factor for a good potting mix is whether it grows healthy plants long term. But I've found you can separate a good mix from a poor mix by doing some easy observations before you use it for plants. Fill a pot with mix and try watering it. Does water flow in easily, or is the mix difficult to wet? Once it's wet, squeeze a handful. Can you crumble it back apart nicely, or does it stay overly wet in a squishy mudball? Does a handful of mix feel spongy and wholesome, or does the wet mix leave your hands feeling slimy, sticky and dirty? Shed the garden gloves and you'll be surprised how much you can learn by hand-analyzing potting mixes.
Here's my analysis of the seven types, with five stars being a high-quality mix.
-Vigoro Potting Mix. Available at home improvement stores, the mix seems composed mainly of bark without enough peat and vermiculite to develop the balance between good drainage while retaining the moisture plants need. Two stars.
-Hyponex Potting Soil. Heavy in the bag, it looks like plain dirt with a little perlite added. Difficult to re-wet when dry, it's too heavy and sticky. Use the package for a doorstop instead of for plants. One star.
-Potting Soil by Greenworld. Available at mart-type stores, it looks like composted bark particles, which would be OK when blended with other appropriate ingredients, which it lacks. Poor bargain mix. One star.
-Premium Potting Mix Custom Blend (a garden center's recommended blend.) Ingredients are peat moss, vermiculite, perlite and bark particles in a nice ratio that accepts water readily, drains well yet retains just the right amount of moisture. I like the wholesome, spongy feel. If it works for greenhouse growers, it's a keeper. Five-plus stars.
ADVERTIsem*nT
-Miracle-Gro Potting Mix. My personal old-reliable because it's available at nearly every mass merchandiser and local garden center, and it grows nice plants. It's a well-researched blend of peat, perlite and processed forest products plus slow-release fertilizer. Five stars.
-Miracle Gro Moisture Control Potting Mix. Supposedly prevents over-and-under watering because it contains coir, which is ground coconut fiber that retains moisture well. This is an advantage for outdoor containers, but I feel it stays too wet for indoor houseplants. Four stars.
-Schultz Potting Mix. Often sold as a price-comparable competitor of Miracle Gro mix, it has more bark particles. It's good also, but not as widely available. Four stars.
Besides these all-purpose mixes, specialty mixes are formulated for African violets, orchids and cacti. My past experience has been positive with the products.
Don Kinzler, a lifelong gardener, worked as an NDSU Extension horticulturist and owned Kinzler's Greenhouse in Fargo. Tune in to his weekly radio segment from 11 to 11:30 a.m. Fridays on WDAY Radio 970. Readers can reach him at forumgrowingtogether@hotmail.com .
