Real Mulch vs. Rocks — Does it Matter?

One of the most frequent questions I get from neighbors is, “Why do you use pine straw for mulch instead of the rocks our landscaper encouraged us to use?”

Pine Straw - mlm cThe first thing to understand is that the sandy soil here is almost worthless, and needs to be amended with good top soil, cow or chicken manure, or compost, then covered with a good thick layer of a biodegradable mulch that will continually nourish your plants and trees, retain moisture, keep roots cool, and prevent weed seeds from getting enough sunlight to germinate.

The second thing to understand is that your landscaper wants your money — as much of it as possible. Rocks are far more expensive than good biodegradable mulch, and aside from being temporarily low-maintenance, there is nothing good rocks can or will do for your plants. Why do I say temporarily low-maintenance? Because they are rarely, if ever, put down in a thick enough layer to keep down weeds for very long.

So many people have asked me about this, I have lost count.  Every single one of those asking moved here from much colder climates where roots grow deep into the ground. Rocks are great in Colorado and Arizona, but not here. Unfortunately,  landscapers pushing rocks got to them before they learned about Southern landscaping or gardening.

“But almost all my neighbors bought rocks…”

It’s true, you do see a lot of planting beds around here covered with rocks instead of mulch — pretty rocks, ugly rocks, river rocks, lava rocks, and so on. 

The short and sweet answer to their question is: “Because, in the Deep South, where roots are shallow, rocks will damage your plants”.

The ugly truth is, in the southeastern part of the United States, rocks are a horrible choice to use instead of a true mulch. There is a longer and more detailed answer, but first, you should know that the best mulch you can use is pine straw, often called pine needles. This is especially true for plants that prefer acidic soil, such as azaleas, hydrangeas, camellias, blueberry bushes, etc. The 2nd best is pine bark chips, often called “nuggets”.

Cypress Bark is Good, Too, But…

Cypress Bark - mlm c@Most people who have always lived and gardened in Florida use either pine straw or pine bark, but many use Cypress bark for its pretty reddish color.

Unfortunately, commercial producers of Cypress bark have come very close to eradicating those beautiful cypress trees. So, if you like the Cypress tress, please don’t buy cypress bark.

The Downside of Each:

It’s true that pine straw needs to be replenished at least once per year, sometimes twice per year. Mine is long past due. You can stretch it to last a year by doing what I call “fluffing” it periodically to expose the dark, rich, reddish-brown color, as the exposed side turns grey. I simply rake mine around a bit every so often. 

Bark chips will need to be replenished less often. On the other hand, bark chips have a tendency to wash out into your yard and onto your driveway during a hard rain. Also, and this is very important, if you have a frame house, DO NOT use wood chips or bark chips of any kind near the foundation of your home. You will be inviting termites.

The downside to rocks is that a) they will damage your expensive plants and trees and, b) they provide absolutely no nutrients to the soil.

If you insist on using rocks, at least use lava rocks. They are not as pretty, but they are porous, and, according to local master gardeners, not quite as bad for the plants.

If you like the Cypress tress, please don’t buy cypress bark.

Even though our community does not allow soliciting by local vendors, they come into the newer neighborhoods while the gates are up for construction crews, and sub-contractors. Within days of moving into our new home, a man rang our doorbell and proceeded to tell me how good his company was, and that he would remove “all that nasty pine straw and put in beautiful rocks”.  I quickly replied, “On, no you won’t!” His face gave away that he had never had quite that response before, and he went on to “educate” me on how bugs and other pests get into the pine straw. I couldn’t resist asking him, “Do you really believe bugs don’t get under the rocks? They are outdoors, after all…”   My husband came to the door and said, “Believe me, buddy, you don’t want this job!”

Think twice about buying palms from guys driving through your neighborhood, selling them off the back of a pick-up truck.

If you have recently relocated here, or to anywhere in the Deep South, please be aware:  This is a scam. Some of the rocks are pretty, especially the smooth river rocks. Others, not so much. I’m sure you have heard the old expression, “It’s hot enough to fry an egg on the sidewalk today!”  Well, that is how hot those rocks get; and here’s proof:

Dead Azaleas - mlm c@

The photo above shows three small dead azaleas in a nearby neighborhood, and a crepe myrtle that needs to have it’s sucker growth removed at ground level — but that’s another topic for another blog post. The first azaleas installed there died during their first summer. They were replaced with more azaleas, which also died. They were replaced again with another plant that seems not to be suffering as much as those azaleas. That’s six dead azaleas, plus landscaper charges for removal and installation three times: a lot of money and beauty wasted due to the heat coming off those rocks.

Shallow Roots vs. Rocks

Azaleas, palms, and all tropical plants have very, very shallow root systems. In warm climates such as this, and throughout the South, all plants, even those that do well in cold climates, have shallower roots than the same plants in other locales. Here, most of the roots are within the top 6 inches of soil, many within the top one or two inches, except maybe for the ancient Live Oaks we cherish around here.

The photo below shows the roots of a young elephant ear plant lying on top of the ground. I raked back the pine straw to plant some coleus, and there they were, just lying there. I knew they would be shallow, but I never expected this:

Elephant Ear - Shallow Roots

The next photo shows where I was digging to plant some Creeping Jenny underneath a palm in our front yard. These roots were within the top half-inch of soil. They seem tiny and insignificant, right? Wrong. The largest roots on a palm are about as big around as the pinky finger on an average-sized man.

Shallow Roots of Queen Palm

What’s Wrong With This Picture?

What's Wrong - mlm c@

Oh, so many things. First, of course, is the rocks. Notice the root ball. Not only is it above ground level, it it also covered with rocks. Then the delicate, fibrous trunk is lying on rocks that get scorchingly hot in summer, and so very cold in our few nights of freezing or near-freezing temps. I’m sure the owner of this palm thinks it looks very tropical. Well it does, but this is not the tropical south. Yes, you will see low, curving palms such as this on the golf courses here, but take note:  they are planted in sand bunkers, or mulched with pine straw; and their root balls are NOT above ground. This is central Florida: the land of rolling hills and orange groves; horse country. Installing this type of planting here is similar to someone taking an Aspen from the Rockies and planting it in the low country of Georgia or South Carolina.

If you have a frame house, DO NOT use wood chips or bark chips of any kind near the foundation of your home.

New to This Area?

If you are new this area, before having any landscaping done, look around your neighborhood. You will see that your neighbors who have always lived in the Deep South (no farther north than Louisiana, Alabama, Georgia,  Mississippi, and parts of South Carolina) and, therefore, understand Southern gardening, are using either pine straw or bark chips for garden mulch.  If you are new to this area, please go to the plant clinics or seek the advice of a local master gardener. You will rarely see rocks used in place of mulch in other Southern states, but if you are in another of the Southern states, please consult your local extension service, master gardeners, or botanical gardens  before paying big bucks for this very poor mulch substitute.

10 responses to “Real Mulch vs. Rocks — Does it Matter?

  1. Good info. We also heard rocks absorb more heat and damage roots. That from the county extension folks

    Liked by 1 person

  2. I’m not in the Deep South, but many of my neighbors have replaced their lawns with a rock mulch now because of the drought. I even have some rocks on the paths in my backyard. I can testify for sure that they don’t keep weed out. There are green weeds popping out all over those rocky front yards and along my lava rock paths.

    Liked by 1 person

    • You make a good point, Barbara. I’ve seen that done, too. It works for people who don’t want grass to mow, as long as the rocks are kept away from plants and at least 3 feet away from the trunks of palms and trees. The weeds can be kept down some if there is black landscape fabric (not plastic), and then if their is a thick enough layer of rocks. I, too, used tiny river rock on a path and had the same issue. The problem is that they are so expensive, people usually put just enough rocks to cover the ground. One of my neighbors who has used rocks instead of mulch told me that weed seeds are taking root in the “dust” from the rocks. When it comes to rocks, you just can’t win.


  3. Always a treasure trove of information, Maria, and as always, I’m fascinated with the garden tips for a part of the country I’ve never seen, except in pictures.


  4. I understand the top of rocks can be hot but underneath it is cooler i have about 10 young areca Palms that thrived in bed of river rock around my yd perimeter screening my pool. maybe i planted them deep enough as to here they re affected like the pic above??


    • If you cannot see the flare at the bottom of the trunk, your palms are planted too deeply, but if they truly are thriving, maybe not. Rocks do not add nutrients to the soil, and because rocks are heavy, they compact the soil, causing more problems. Thanks so much for visiting, and for your comment.


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