Tree base stone or mulch?

[kaktree]

Looking for a bit of advice. We have gotten some conflicting advice.
One arborist suggested that we create a 2 inch layer of mulch in about a 2 foot diameter and then cover it with a layer of 2-3 inch diamter river stones.

Another tree service told us that this would kill the tree due to keeping them too warm in the fall.

We live in Duluth MN (Zone 3).

The bases of all the trees are currently covered and they look good. Do you think we need to take all the stones off?

Appreciate advice

 

[S Mc]

I'm not a fan of stone as a top dressing around trees. I have no idea why the one arborist suggested stone over mulch unless he/she was trying to blend or match a landscaping feature in your yard.

The primary purpose of mulch (there are a host of benefits) is to provide an ongoing source of bionutrients to the soil food web within the ground as it breaks down. You will have to replenish this resource periodically. Covering it with stone is going to make that difficult.

I would not go so far as to say the stones will kill the trees. Although they can heat up soil, the soil is buffered by the mulch, they can cause damage by reflecting light.

They do not benefit the trees in any way. There are some who say minerals will be added back into the soil as the stone breaks down. Well, that is possible....on a very finite degree, over a very long period of time depending on the type of stone used. For that to be beneficial you would need to know what the stone components are and if these minerals are necessary in your existing soil and will they benefit the species of tree you planted.

Organic mulch gives back to the soil, which gives back to the tree. It provides many benefits immediately. One of the benefits of a mulch ring is to catch the debris that falls from the tree. This is then allowed to breakdown, looking natural as it goes about its normal cycle. With the rock, you will be cleaning this material off as it becomes unsightly.

You don't mention what kind of species these trees are. If they are a species which is a host to aphids or other honeydew producing insects, you will likely find your stones covered by a black substance, called sooty mold, that is using the honeydew that the insects secrete as a substrate. This may then cause you to call in a pesticide applicator who will then recommend that you "treat" the trees to suppress the insect problem. Then comes a spiral of combating the insects the natural predators may have been able to control, but can't now because they have all been killed with the aphids.

Ok, now I'm just getting on a rant here...short answer: No, the stones won't kill your trees. But yes, I would remove them and stick to organic mulch.

Sylvia

 

[A10egress]

+1

I ringed my trees on the front lawn in stone and while it looks nice, its a bear to keep clean in the fall with the leaves.

On my street ( damn i hate suburban life) its kinda like "keeping up with the Jones" and the stone / belguim block looked better for my front lawn than the mulch did.

The plus is, its kind of a once and done buying experience opposed to buying mulch every spring. It is , however a little more maintenance and offers no organic material payback.

 

[pdqdl]

covering mulch with river stones sounds like insanity.

As a professional landscaper, as well as an arborist, I can assure you that the river stone will begin to fill with organic material, eventually forming a concretion of earth, organic detritus, and the river rock. It will be impossible to refresh the mulch layer beneath.

Depending on the density of the shade under your tree, it may begin to grow weeds, too. When you pull them, it will continue to mix mulch with rock, and that lovely rock circle begins to look pretty poor.

When it comes time to refresh the appearance of a river rock layer, the only practical method is to scrape it all out, and replace with new. The cost of this service is MUCH higher in labor and materials than for mulch alone. Unless you are willing to pay considerably higher long term maintenance expenses for a good looking landscape, skip the rocks.

Rocks work well in locations where they can be laid over a heavy plastic barrier to prevent weeds. Even then, it usually comes at a higher long term expense to keep it looking good than either mulch or grass.

Use plain old mulch, plant some shade tolerant landscaping under the tree, and plan on pulling a few weeds. Some of the very best landscape plants (both for colorful flowers and interesting appearance) are shade tolerant. Spend your maintenance dollars on boosting the landscape with nice perennials mixed with annual color, and NO ONE will wonder why you didn't just throw some colorful rocks on it.

More reasons to prefer mulch: Mulch is easier to clean in the fall leaf drop, and doesn't migrate out into the lawn with as many problems as rock. Rock gets kicked out into the lawn, and you must pick each little stone up by hand and throw it back.

 

[ct greenman]

the mulch is great stone not good retain heat and detour water from getting to the roots. I would ditch the rocks.

 

[A10egress]

I placed weed preventer fabric down, then ringed the tree with some large Belgian block, then filled with river stone. I have found that every other year, i need to pull the stones, clean it free of weeds and organic material then replace the cleaned up stones. Sure, its a lot of work too, but i guess its all in the look you're going for. My trees are growing just fine with this arrangement.

 

[oscar_e_leon]

I wonder if this reply will be read! I oversee our Church garden and a few years ago we renovated our gardens, which included a hedge of 55 Little Gem Dwarf Magnolia trees along the front perimeter of our property. Unfortunately, the vast majority of them were planted too deep. We only found this out after the job was done and we had a professional arborist evaluate our site. The root flare was anywhere from 2-6 inches too deep, some as deep as 8 in. I had to excavate the dirt to reveal the root flares around all the trees. Now we have "wells" around most of the trees. I gradually have been removing some of the dirt around each base to try and level out the depth differences in the surrounding soil. I have also had to keep removing debris/mulch from filling back up in the wells so as to keep the root flare exposed.

We've had a couple arborists over the years suggest covering these wells with small river stones (about a couple inches in diameter) to keep debris out, and also to make it look kind of decent. After reading the above posts, I'm not so sure how good of an idea it is, though I see very little other option. I've already covered about 8 tree wells with these stones ("pond pebbles", to be exact), with an average diameter of about 1.75 ft (the trees vary in size but average around 8.5 ft tall and 4.5 ft wide). We were advised not to fill the wells with mulch as this would keep too much moisture around the root flare and above the root flare, and eventually the mulch would decompose into dirt, and we're back to where we started.

Does anyone have any thoughts and/or suggestions on this?

 

[ATH]

Couple of mentions of weed barrier above... That is my main concern with rocks is that people will put that inder the rocks. It is not good for the trees...limits O2 and CO2 exchange between soil and air, limits water penetration and prevents composting organic matter from benefitting the soil below.

Without weed mat my only concern would be if you are using limestone that it will raise the pH...but that will take a long time.