hi tj,

yes landscape fabric is 99% of the time put under it

Gravel is about the same density as soil because of the air pockets in between. Maybe a little heavier but not much. So, the pressure on the top of the soil under, say, 4" of rock is about the same as the pressure 4" down in a bed with no rocks on top. In other words, not a big deal.

Soil does tend to get dry and hard under plastic and gravel because 1) water isn't infiltrating so it dries out and 2) there isn't much input of air or organic matter either, so there isn't much biological activity in the soil, few worm holes or other activity keeping it porous.

Thank you tox. I know you said plastic but what about landscape fabric? This fabric in particular that I have seems to really let air through. It is almost see through. As far as water, i have a drip hooked up at the bottom

I read a lot of split opinions on landscape fabric and whether or not it is bad for soil

i would normally try to use cardboard to replace fabric and act as a weed barrier But a significant issue im running with cardboard is that it actually wicks moisture up away from the soil when im watering.

I live in San Diego so moisture is a huge issue here

The fabric is probably better than plastic because it will breathe and let water drain through. It will help somewhat to keep the gravel from sinking into the soil. Just don't be too confident that it will keep them separated forever, or that there will be no weeds growing out of the gravel. For one thing, wind will deposit some soil (dust) and bits of organic matter over time, which will become soil at the bottom of the rock layer, and then weeds can sprout and not have to grow up through the fabric. So it's a good idea to keep the gravel surface clean. Blow or rake leaves off of it, for example.

Do NOT put landscape fabric under rock mulch. It's horrible because it traps dust, then weeds sprout in the dust and put roots through the fabric and when you pull weeds they pull the fabric out of place too. You can't use a scuffle hoe on it because it snags and damages the fabric.

Plain gravel can be raked, weeds pulled and scuffle hoes used on the surface easily.

Rock mulch does not compact dirt any more than dirt does - it's the parking and walking and driving on it that does the compacting.

In addition to lazy's comments, the pores in landscape fabric will clog (usually around year 3) and any breathing it does will cease, and without air, water and nutrients the soil below basically dies as it becomes lifeless.

tj

There are certain topics where It's more useful to find a brick wall and bang your head against it. As soon as the words fabric or plastic entered this discussion, it was over.

I'm not going to debate most of these points and the OP has to make their own decision. Just wanted to say, whether gravel is rakeable depends upon the size. Pea gravel will act quite differently from 1" gravel and 1-1/2" lava rock and 2-4" rounded river rock. It will get weeds in it eventually no matter what you do. I have a gravel side driveway and I try to keep it cleaned off of fall leaves and pull weeds when they appear so they don't go to seed. It's stayed relatively weed free. I never paved it because I like the fact that it lets rainwater infiltrate rather than run off into the street and then the creek.

Whether rock, stone, pea gravel, etc. would compact soil will depend on how deep the material is piled on the soil. With most installations that would be about 3 to 4 inches and would not be enough added weight to compact soil very much, at least where I have put that type of mulch down it has not.

Whether to use landscape fabric under any mulch is a choice each gardener needs to make. Landscape fabric can help suppress unwanted plant growth ("weeds") for a time, but many of these unwanted plants will root in the fabric over time. Also over time dust and organic material will accumulate in that rock mulch and allow unwanted plants to grow and will require (as I have found) periodic cleaning to prevent that growth (like every 3 to 5 years). Of course, one could spray plant poisons that might help control this unwanted growth.

i wanted to extend on this question a bit more after i got these great answers so thakn you to everyone! so as long as the weight of the rock isnt too much, the soil should be just fine.

what about when there are thick concrete blocks or stacks of bricks directly over the soil? i assume this would compact it seriously and make it inhospitable?

i often see tree and shrub roots make their way under heavy pavements, brick and concrete wall blocks. for example, in my backyard, there was a 5 foot raised bed installed with concrete blocks stacked on top of each other. right next to that, no more than a few inches away, the trunk of a citrus tree with roots that are all under the raised bed. shouldnt the weight of the 5 foot concrete blocks and the weight of the 5 foot soil be making the soil beneath the 5 foot mark too compacted for the roots to colonize? this was done by the previous owners and we really like the citrus tree and would like to save it if there is an issue of the concrete blocks "smusing" the roots and the soil around it

additionally my neighbors yard and my own are separated by a large retainer wall. they have a lemon tree hiked up right next to the retained wall on their side that had been planted AFTER the construction of the wall. its roots are shooting over to my yard and going through any soil that has compaction exerted by the retainer wall