Is It Safe To Put Red Mulch Under A Home Grown Veggie Garden In Southern California?

Maria is a master gardener and master of public health. She & her husband, known online as The Gardener & The Cook, live in coastal Alabama.

A thick layer of pine straw mulch will keep soil cooler and will keep weed seeds from germinating.

Maria Logan Montgomery

When we lived in central Florida, one of the most frequent questions I got from neighbors is, "Why do you use pine straw for mulch instead of the rocks our landscaper encouraged us to use?"

The First Thing to Understand

The first thing to understand is that, in the south, roots remain shallow, and the sandy soil in Florida and along the coastal plains of other states is almost worthless. For successful gardening it 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 do these four things:

continually nourish your plants and trees;
retain moisture;
keep roots cool;
prevent weed seeds from getting enough sunlight to germinate.

The Second Thing to Understand

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 although they are temporarily low-maintenance, there is nothing good rocks can or will do for your plants.

Why do I say temporarily low-maintenance? Because the rocks are rarely, if ever, put down in a thick enough layer to keep down weeds for very long. Soil, dust, and decomposing leaves will filter down among the rocks, providing the ideal place for weed seeds to germinate. So, using rocks will not prevent weeds.

Rocks Are Fine in Cold, Harsh Climates

So many people asked me about this, I lost count. Every single one of those who asked had moved there 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 throughout Florida covered with rocks instead of mulch – pretty rocks, ugly rocks, lava rocks, river rocks, and so on.

The Worst and Best Mulch to Use

The ugly truth is, in the southeastern part of the United States, rocks are a horrible choice to use instead of a true, biodegradable 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 Second Best is Pine Bark Chips, Often Called "Nuggets"

Pine bark nuggets often float out of place in a hard rain.

Maria Logan Montgomery

The Downside of Pine Straw and Nuggets

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 tend to wash out into your yard and onto your driveway during a hard rain.

Also, and this is very important, DO NOT use wood chips or bark chips of any kind near the foundation of your home. You will be inviting termites.

Cypress Bark is Good, Too, But...

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 trees, please don't buy cypress bark.

Cypress bark mulch is loved by some for its color.

Maria Logan Montgomery

Imitation Cypress Nuggets

Recognizing the desire for the reddish color, some commercial companies began dying pine chips (not pine bark) in a color that looks like cypress bark. Master gardeners recommend against this product because we don't know what the dye will do to the soil and to plants and trees.

If you like the cypress trees, please don't buy cypress bark.

— Maria, Master Gardener

The Downside of Rocks

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

Those Sneaky Guys Who Call Themselves Landscapers

Even though the community where we once lived did not (and still does not) allow soliciting by local vendors, they still go 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..." I then told him that any master gardener would tell him pine straw is the best mulch there is. He sighed, and went away.

It's Hot Enough to Fry an Egg on the Sidewalk

If you have recently relocated to anywhere in the Deep South, please be aware: The pushing of rocks 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:

Azaleas simply have too shallow a root system to be planted in rocks.

Maria Logan Montgomery

Six Dead Azaleas

The photo above shows three small dead azaleas in a neighborhood near our former home, and a crepe myrtle that needs to have its sucker growth removed at ground level – but the myrtle is another topic for another day.

Not knowing that crepe myrtles don't like shrubs to be planted under them, the homeowners had the first three azaleas installed there. They died during their first summer.

They were replaced with three more azaleas, which also died. Those were replaced again with another shrub that seemed not to be suffering as much as those azaleas. All of the azaleas were the Encore brand that can take more sun, but that's six dead azaleas, plus landscaper charges for removal and installation three times: a lot of money and beauty wasted due to the intense heat coming off those rocks.

DO NOT use wood chips or bark chips/nuggets of any kind near the foundation of your home. To do so is to invite termites.

— Maria, Master Gardener

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, except for large trees with huge root systems, most roots are within the top six inches of soil, and are many within the top one or two inches.

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 them to be on top of the soil.

Shallow roots of this young elephant ear are running across the surface of the soil. They would have been damaged by rocks.

Maria Logan Montgomery

What's Wrong With This Picture?

This palm died a few months after I took this photo. No surprise there.

Maria Logan Montgomery

Oh, So Many Things Are Wrong With That Picture

First, of course, is the rocks, but notice the root ball. Not only is it above ground level, exposed to hot sun, it is also covered with rocks. Additionally, the first 8 to 10 feet of the delicate, fibrous stem of the palm is lying on rocks that get ridiculously hot in summer, and so very cold on the few nights of freezing or near-freezing temps. (That's right: palms have stems, not trunks, but that, too, is another topic for another article.) I'm sure the owner of this palm thinks it looks very tropical – well it does, but that palm is not the tropics.

This photo was taken in central Florida: the land of rolling hills and orange groves – horse country. Installing this type of planting there is similar to someone taking an Aspen from the Rockies and planting it in the low country of Georgia or South Carolina.

"But Low-Lying Palms Like That Are on the Golf Courses…"

Yes, you will see a few low, curving palms on the golf courses there, but take note: they are planted in sand bunkers, or mulched with pine straw, their root balls are NOT above ground, and the stems are not lying on rocks.

New to the South?

If you are new the southeastern United States, look around your neighborhood before having any landscaping done. You will see that your neighbors who have always lived in the Deep South (no farther north than Louisiana, Alabama, Georgia, Mississippi, and the Carolinas) 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 before spending money on landscaping. You will rarely see rocks used in place of mulch in southern states other than Florida, 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.

Enjoy Your Garden, But Don't Waste Your Money

If you love gardening as much as I do, I know you'll want to do what's best for your plants. Following local guidelines for your area will ensure that your plants perform at their best for you. Happy gardening!

This content is accurate and true to the best of the author's knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

MariaMontgomery (author) from Coastal Alabama, USA on August 20, 2021:

Thanks so much. I'm glad you enjoyed this article, and found it helpful. I'm so sorry you lost your myrtle. Maybe try another one when you can. The ones with the spreading canopies offer nice shade.

The ground cover idea is nice. There are several ground covers I like, but I don't have any right now. Gotta work on that.

I've heard people say they don't like the looks of pine needles. I actually love them. Growing up in the Birmingham area, we always had lots of pine trees, and all I had to do was rake them into place around my azaleas, etc. In Florida, and here I've had to buy them. About 18 months ago we had 7 pines installed, 4 in the front yard & 3 in back. They've already almost doubled their height, so we will get some needles this fall, but not enough. We'll be buying them for a few more years yet.

Shauna L Bowling from Central Florida on August 20, 2021:

Maria, this article is packed with information any gardener who wants to succeed should heed, especially those of us who live in the South.

I've known pine straw is the preferred mulch, but I don't have pine trees in my yard and I really don't like the looks of pine needles. In my smaller beds, I simply rake fallen oak leaves into them or let the ground cover I have planted fill in the bald areas. In larger beds, I use eucalyptus mulch. What are your thoughts on that?

I wasn't aware of the hazards of using rocks in place of mulch, but what you say about them getting fry-an-egg-hot makes perfect sense. I used to have marble rock around a crepe myrtle that seemed to decline as each year went by. Now I know why. I ended up having to remove it from where I had it because our city has converted us from septic to sewer. The line running from the main line to the road runs right through the area where I had the myrtle planted. I ended up giving the tree away. Hopefully the new owners are taking better care of it.

Great article. I really enjoyed the photos and lessons learned!