Gardening Q & A: What’s the dirt on potting soil? It’s getting complicated. – Virginian-Pilot

Recently, on a rainy day, I found myself snooping around the hard goods section of a local garden center. I was astounded by the number of “potting mixes” that were available for sale. I counted 10 or so. And in one big-box retailer just down the street, I counted 18 different ones. Years ago, you’d be lucky to find two or three options.

I find this about as difficult as picking a salad dressing from a quarter aisle of them in the grocery store. Can you remember when all you had was about five choices? Life was simple then.

All of these options in choosing a potting mix is darn confusing. First of all, it’s the names. You’ll see potting mix, potting soil, potting media, potting substrate, etc. One national company has “garden soils” specifically for vegetables and herbs; flowers, trees and shrubs; roses – and an all-purpose for in-the-ground use. The same company has “potting mixes” for indoor potting, orchids, moisture control and seed starting. Additionally, they have an organic line – and then there’s the individual-mix components like sphagnum peat, vermiculite and perlite.

Are you getting dizzy?

Just what is in these mixes and soils, and what distinguishes one from another? Is the cactus, palm and citrus garden soil really different from the cactus, palm and citrus potting soil?

The confusion stems from the fact that there is no state or federal regulation of these products, much like there is no legal definition for topsoil. Producers can formulate these using a wide range of ingredients. The label details can vary greatly by product or state. On one respected company’s bags, different ingredients are listed for different states. Interestingly, those being sold in Virginia and North Carolina (where I took the photo), did not list either state on the label. So what exactly is in our bag?

Many of these products now include fertilizer. I did note that this is spelled out precisely on the back of the bag, as is required by law on fertilizer packaging. The analysis and nitrogen sources were given.

All I can say is pay less attention to the name on the bag and focus on the ingredients inside. Look around for a broken bag, and take a closer look, grab a handful and feel it. At Tidewater Community College, for 30 years we got by just fine using two base mixes for greenhouse crops. Sometimes less is more … better.

I’m out of space this week. This is a big topic. I’ll drill down on some basics related to this very important subject in the future.

term of the week

Monoecious – having both male and female reproductive structures on the same individual. The word means one-house. Last week, I mentioned that cycads are dioecious. Pines, on the other hand, are monoecious, as you can see from the large (female) and small (male) pollen-bearing cones, together on the same plant. Do you know what sex your plants are?


Q. I have what I believe to be a variety of a Japanese maple tree that flourishes from early spring to late summer. The problem is, when late summer arrives, the leaves shrivel and get a fungus, and they drop off like there is no tomorrow. What can I do to prolong the beauty of the tree and rid it of the fungus? – Vince Tretola, Chesapeake

A. Are you familiar with powdery mildew? Your photos look like it. Please see this article from Clemson ( that discusses the causes of and treatments for powdery mildew.

A number of spray materials may give you some control. These include Thiamyl, neem oil and horticultural oil. These are all nonrestricted use materials, but be sure to carefully follow label recommendations.

A homemade remedy, known as the “Cornell Formula,” may be worth a try. The recipe is: 1 tablespoon baking soda, 1 tablespoon horticultural oil, and 1 to 2 teaspoons horticultural soap or dish soap, all added to 1 gallon of water and sprayed.

Additionally, rake and dispose of leaf litter.

and one more thing …

Mark your calendar for this Wednesday. The June solstice marks the start of astronomical summer in the Northern Hemisphere. The sun reaches its northernmost point and the Earth’s axis tilts directly toward the sun. Sunrise in Norfolk will be at 5:46 a.m. and sunset at 8:27 p.m., according to, making Wednesday the day with the most hours of daylight this year.

Having a summer solstice party? Plan on staying up late; summer officially begins at 12:24 a.m. Eastern Daylight Time.

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