Rocks vs mulch: which is better

[James B]

Question about what’s the better overall material for most subtropical palms. Stones have the advantage of heating up especially in sun the area around the base of the palm. Mulch can keep moisture in better. For our climate with hot dry summers and cool wet winters what is the better option for year round growth and health? The palms I’d be asking about are Archontophoenix, Roystonea, Chambeyronia, Chasalidocarpus, Wodyetia. Would make up the bulk of palms in this scenario. 

[JubaeaMan138]

If I had the cheddar to do all my planters in rock I would do rock 100 percent I usually tend to plant most of my palms in a deep dish style basically in a big bowl below ground level and then I fill that with rock keeps squirrels and the pups from digging around plants as well . 

[JubaeaMan138]

I think In our area of  the inland empire we get plenty of heat and are borderline on the cold side. . We can grow some great stuff all of those species you listed I would plant in shade here minus wodyetia  and royals and even royals so far for me they have appreciated some shade early on . Then about big 5 gallon size they do good in full sun . Either way in shade I still backfill my plantings with rock . Our biggest enemy here is cold wind . 

[jwitt]

Rocks in my zone 7b

[96720]

I use 100% mulch it is not only helps hold on moisture but as it breaks down it also feeds the palms and worms love it to help break it down I am continually adding more mulch !!!! I grow almost all the palms mentioned and they all do great!!!

[Silas_Sancona]

My thoughts on this are obvious, I'm a rock junkie, 😁  Cleaner look, and doesn't need to be refreshed all that often due to wind or water-related erosion..  Rock also drains away surface water better, ..but can retain moisture below the rock layer pretty well.

That said, what size / color stone / gravel you use, **if you go that route** is important.. 

If the heat in summer is as brutal there as it can be here, dark colored stone is a recipe for burning -just about anything, even tough cacti, esp. if the area where it is laid down is in sun all day.. Big rock, ...say stuff like river / cobble stone bigger than about 2" in diameter is tougher to clean through, vs smaller sized gravel ( say 1/4th inch sized Granite ) which is easy to rake out / blow through when needed.

Geologic history of the type of stone is a factor worth basic research too since, for example, Granite / Lava - type rock will usually contain lots of trace minerals, and decent amounts of K which will be continuously released into the soil below.

Stone mined from Marine-based deposits, ...Limestone for example, will release different elements over time ...Say higher levels of Calcium, vs much lower levels of K.  Limestone-based rock will also be more Alkaline compared to Granite or Lava ( typically considered slightly Acidic in nature )

Depending on space and budget, you could do a couple different types  / sizes of stone, ...say 1/4th inch Granite for the overall bed(s), w/ larger rock scattered in the bed(s) or laid down along the bed's edge..  and, using Jubeaman's idea, dig your planting holes like a bowl, and apply Mulch in those spots, esp. around palms that like being mulched..  That way those palms get what they want, but you're not constantly refreshing yards and yards worth of mulch over large areas. You could do the same thing, minus the mulch, and offload any leafy yard debris into those spots too..

One thing of note: As mentioned a few times before, some people assume that by using stone / gravel as a mulch, no organics will ever get into the soil.. That isn't truth..

If you leave some fallen leaves on the stone, esp if you incorporated trees into your beds / overall yard that drop small, fern-like leaves like Royal Poinciana, or Schizolobium, whatever amount of that annual "duff" you allow to remain will work it's way down through the stone to the soil below. 

At the old house, i had everything from worms / other insect decomposers, to Mycorrhizal fungi and Mushrooms pop up through the rock at various times of year. While i didn't install Palms specifically, what was planted grew well...  My only regret w/ that lay out was i should have used a different colored, larger stone, where i installed that sized rock in that yard..

Again, just thoughts..

[Looking Glass]

Depends a bit on your soil too.   I throw down mulch and chop up everything I can, and toss it in too.  Otherwise, it’s all sand, over a coral reef deep below.  Holds no water or nutrients.  Only certain palms can be happy in that.   Digests rapidly in our humidity.  I add more around twice a year.   Underneath is all worms and white fungi doing their work.  

I do use shell mulch and limestone around the Carribean stuff and Pseudophoenix though.  To keep it drier and more alkaline.  

I’ve also got riverrock around the fence border and my neighbors whole front yard is grass-free, with stones covering the open areas.  The only trouble with that is that the weeds are relentless here.  They grow in constantly in ever crevice and crack and in between every stone.  Requires a lot of weeding and spraying to keep up.   

Rocks do look great though when you keep them tidied up.  
 

 

[Fishinsteeg234]

In wet and humid florida I believe mulch is king due to how it naturally balances the soil and works symbiotically with the plam, or any high nutrient or water loving plant for that matter. Mulch breaks down from the fungus and bacteria levels and feeds all other larger organisms up the food chain, turning the mulch and compost into a black gold soil layer. Palms with a 6” thick, 4’ foot wide mulch ring around a palm will thrive due to the breakdown process creating an earthworm haven and moisture retaining bio-layer to keep the palm naturally happy. Mulch should be re-applied regularly to retain moisture, keep weeds at bay, produce heat from natural microbial breakdown, and keep the microbial ecosystem balanced how nature intended. As in the rainforest, fallen leaf/plant debris breaks down same way and feeds the whole ecosystem. 

[RyManUtah]

I prefer rocks. Wood chips do not stay in place in, and break down too quickly in the sun. Rocks are less likely to wash away when it rains also. Rocks also help mitigate the affects of the cold, winter wind - and are readily available. If I lived somewhere that didn’t go up to 5 months between rainfall, I would probably consider non-rock mulch. Otherwise, mulch is just a messy magnet for roaches. 

[sonoranfans]

Have had both, and each has its advantages in the right areas/soils.  Rock is superior in the hot desert, mulch is superior in subtropical FL.  Yes as mentioned the soil is a big factor.  Rock plus clay is a winner since clay holds lots of water and has cation exchange capacity.  Mulch is not really needed if you have clay.   And in the desert, the rock protects the roots from heat better and evaporation is slower through the rock.  I lived in the desert 10 years with clay based soil, mulch on top dried out very quickly and blew away.   With clay under rock it will be wet for days after a deep watering.  Evaporation is driven by (low)humidity the wetted surface area/air interface, mulch has far more wetted surface area than a 3/4" rock, probably 20-100x more.  If I am in Temecula (a desert area) or riverside etc, I would take rock in a heartbeat if the soil was clay based.  If the soil is sand I would add clay and some organics, sand in hot desert areas would be a disaster for most palms.  Sand drains fast, dries out the fastest so you would need to water a lot more.  That rock/clay combination is remarkable in its water retention/heat protection.  My yard in arizona was 3/4" granite rock, in florida its all mulch no rock.  You have to take what nature gives you and if water is expensive, make a plan to keep it around longer.  In the dry desert, mulch has too much wetted surface area and drying is rapid, in Florida its the opposite, evaporation in high humidity is slow and sandy soils require the addition of cation exchange capacity.

[HiwaKika]

Another point: squirrels dig thru mulch and bury acorns but don't mess with rocks. I use lava of various sizes.

[Silas_Sancona]

1 hour ago, HiwaKika said:

Another point: squirrels dig thru mulch and bury acorns but don't mess with rocks. I use lava of various sizes.

This is a good point.. Birds, esp. Thrashers, will tear through ..and bury seeds in mulch, here at least. Know Scrub Jays, and some other birds do their own seed planting out there.   Cats + Mulch?.. Don't even get me started, lol.   See much less of that using stone.

On the other hand, small rock might not fully deter Gophers.. -If you're lucky enough to have a few around .  I have at least one here that has made a mess in a few spots where i laid down gravel, let alone the "Ankle traps" it makes which lie hidden below where there is lawn in the back yard. 

[Phil Petersen]

Personal perference but I definitely prefer woodchips/mulch. My soil is clay, so mulch improves drainage, feeds the soil biota, lightens up the soil texture, and is much easier to weed. Mulch builds better soil whether you have clay or sand.

Rocks I find are very heavy to import and spread, and hard to manage as they get mixed into the soil and stay there if the soil is disturbed. Weeds can grow through rocks/gravel as well so you are faced with having to pull out weeds with difficulty etracting the roots  from unrenriched  hard clay below.  Weeds come out so easy if they manage to grow in mulch as their roots are so loosely held I can pull them out between a finger and thumb. Aestetically, I personally prefer the look of woodchips/mulch in the garden and dont think I will try rocks/gravel again.

[Gottagrowemall]

I don’t use rocks anywhere because they’re harder to find and harder to keep weed free. I think mulch is healthier for my plants too. Only downside to mulch is it creates more moisture and potentially moldy/mossy ness on the palms. 

[Tracy]

I have had the benefit of reading all the other posts and ruminate on this.  Some of the best gardens I know here in Southern California put down a great deal of mulch before planting their gardens.  One of the complaints about mulch that is mentioned above is that it doesn't stay in place.  So a potential solution is put down a thick base of mulch, then add the rock on top of that so it stays put.  Nathan provided some good ideas on selecting rocks for the desired nutrients from their slow degradation (limestone for the Caribbean palms like Copernicia and Coccothrinax, versus granite or lava for more acid loving palms like Chrysalidocarpus). 

While your question is a little open ended and subject to opinion's based on where one is, type of soil, amount of rain etc., I think you were looking for specifics for your garden, Southern California inland empire climate and soil.  Knowing how windy it gets in Rancho Cucamonga, the suggestion of putting down some rock around freshly planted palms might help anchor them until they establish decent roots.  You do get hot as well in summer, so lighter color rock as was suggested would also be smart for exposed areas.  That said, I do love the look of a dark lava rock.  Dorian who lives here in Leucadia and had his garden on the Palm Society of Southern California tour back in 2019 has used lava rock extensively for borders and walkways.  It gives a very tropical feel to the garden, so perhaps if you have a shaded area, you might still be able to use some lava rock in areas.  Just like you might plant more sun tolerant and less thirsty plants in your most exposed south, southwest and west facing areas, you will be more likely to plant your more shade demanding plants on the northern areas and eastern facing areas so could change the rock them a little.

Take your time and do things right for your soil.  The result will be that your palms as well as other plantings will appreciate it.

[96720]

I don’t have any problem with mulch blowing away I find that it holds better to slopes and keeps the dirt from washing down hill in heavy rains, you can also get free fresh wood chips from tree services if you have room for a full load!!!

Edited November 28, 2022 by 96720
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[Moose]

On 11/26/2022 at 9:29 PM, Fishinsteeg234 said:

In wet and humid florida I believe mulch is king due to how it naturally balances the soil and works symbiotically with the plam, or any high nutrient or water loving plant for that matter. Mulch breaks down from the fungus and bacteria levels and feeds all other larger organisms up the food chain, turning the mulch and compost into a black gold soil layer. Palms with a 6” thick, 4’ foot wide mulch ring around a palm will thrive due to the breakdown process creating an earthworm haven and moisture retaining bio-layer to keep the palm naturally happy. Mulch should be re-applied regularly to retain moisture, keep weeds at bay, produce heat from natural microbial breakdown, and keep the microbial ecosystem balanced how nature intended. As in the rainforest, fallen leaf/plant debris breaks down same way and feeds the whole ecosystem. 

I agree

[Jim in Los Altos]

My number one goal is what’s best for the health of my palms. Wood mulch is far superior to rock mulch if your goal is healthy soil with worms and beneficial microorganisms. 90% of my garden is wood mulched and 10% has pebbles in a few shaded areas. I have hundreds of bromeliads growing throughout my landscape which wouldn’t be possible with rock mulch. A thick layer of wood mulch adds some heat too as it breaks down.