Do I have to remove mulch before adding rock?

[Loren Ver]

Hello,

DH and I have an art garden that is getting an upgrade and we are moving from mulch which is difficult to maintain to river rock.  The area is rather large and currently covered in mulch.  We are debating back and forth on if we need to remove the mulch (which does have a weed barrier underneath) before adding another weed barrier and river rock.

We will be the ones doing all the work, so this will be days of shoveling, so if we don't have to shovel twice I am all for that.  But if the old mulch is just going to make life in the long run harder, then better to shovel now than be sad later. 

Right now the plans is spread it out and level it the best we can then cover it in tons of rocks.  My guess is the tons of rocks will mitigate any issues :).

Specifics:
Mulch up to 3" deep in some spots and spongy when you walk on it.
It is about 14 yards of material - so a lot of moving.  My poor arms.

Thanks for any input!

Loren
 

[neo von retorch]

How deep are you making these rocks?

I would think that mulch which is wood is going to be nutrient rich soil sooner rather than later, so a layer of that on top of your weed barrier seems like a recipe for growing lots of things that pop up through the rocks. Our neighbors put their own river rocks down about a month ago, and they already have a lot of green peaking through them... we paid someone to do it; they dug it out, put down new weed barrier, and then put down a couple inches of medium river rocks. So far nothing coming up, but we'll have to see how it lasts over the years.

[Loren Ver]

We'd be putting a new layer of weed barrier over the old mulch to control weeds.  We generally apply herbicide to areas before putting down weed barrier to kill off the stuff that might still be trying to grow up through the barrier. 

River Rock 2-3 Inches
------------ (Weed Barrier)
Old Mulch
------------ (Weed Barrier)
Ground

Our main concern is if that organic layer sandwiched in the middle will cause problems down the road.

[lthenderson]

I would probably opt to remove the mulch layer and old weed barrier and start with a new barrier on native soil. My concern with adding a second layer of weed barrier on top of the much and first layer of weed barrier is that the sponginess of the organic layer could cause the new layer of weed barrier to be punctured by the weight of the rocks and thus compromise it. I would also be concern with mold being formed between the two weed barrier layers and affect what ever might be planted in those beds. Finally, if you ever go to plant something there, dealing with the rock and two layers of weed barrier would be a nightmare and perhaps hamper the plantings from actually obtaining the proper moisture and nutrients.

We have river rock landscaping in several beds around our house over a single layer of weed barrier and it has worked well though we did closer to five inches of rock. I use a leaf blower a couple times a year, late fall and early spring, to blow all the leaves and accumulated debris out of the beds to prevent any organics from building up as long as possible and potentially give future weed seeds places to root.

[Paper Chaser]

Mulch needs to go to do it right. Signed- guy that did the same thing and put down 36 tons of river rock

[Loren Ver]

Looks like we are going to need a dumpster.

[yachi]

I'll put this here for whoever to think about.  I'm in Pennsylvania, where it's getting things to *not* grow that's the trick.  Leaves, sticks, pollen, and other parts of long-dead plants decompose on top and around river rock.  How long this takes depends on your climate,  of prevalence of trees, and how on top of maintenance you are.  If you have lots of trees, 2 or 3 seasons of not racking or blowing out your rock garden is enough to provide plenty organic material for things to grow between your rocks.  I suppose it also depends on how deep your rocks are, as some organic material will filter down through the rock as it decomposes.

[neo von retorch]

I'm in Pennsylvania, where it's getting things to *not* grow that's the trick.

Same. Rocks and mulch and all the tricks are all basically to fight nature 🤣

[Dicey]

Tagging on to this convo: A few years ago, we dug out the front lawn, put down a high-quality weed barrier, then dumped a full belly dump truck of good-sized slate chips on top of it. We did this because we have Redwood Trees, which are not grass-friendly, and we live in a drought-prone region. We got a great deal by buying a double truckload (the rock from the second hauler went to the side and part of the backyard), and shoveling it ourselves. The rock layer is at least six inches thick. Guess what? We still get weeds popping up from the rocks. At least they're easy to pull, provided you get them before they send their roots down through the rock and the weed screen.

Our neighbors were thrilled when the semi pulled up at 6am in a Friday morning in December. It was a fun weekend.

My point is that there is no such thing as effortless landscaping. Anything you do requires ongoing maintenance, just hopefully less of it.