I meant to ask about this in another thread, but thought I’d start a new thread. When I was at the orchard recently, I noticed that they often use gravel for their mulching. It would seem to be a good way to keep the weeds down, without having to worry about continually replacing wood mulch products.
I mention this because over the last couple weeks I’ve been weeding and adding new mulch around all my new trees, and it’s been a chore. Being the lazy fellow I am, I was maybe considering the gravel approach.
Of course, gravel doesn’t break down, and add organic material to the soil like mulch would.
In organic farming, gravel is sometimes used for mulch because it is within the Certified Organic code to control weeds by blow torch. Never mind the amount of pollution that is released into the air.
The folks that do this professionally rely on liquid (or dissolved) fertilizers to feed their plants/trees so the issue of lack of organic mulch is less of a problem.
Out here in the western U.S. it can be problematic because rock retains heat really well and increases evaporation of water from underlying soils.
I haven’t tried it on trees but I did on my grapes (flat rocks and gravel). The weeds weren’t much impressed and found ways to grow in any little nook or cranny, and they were much harder to get out IMO, and not so much fun to work around. I probably needed more to really keep the weeds out. But when I dropped a few of my precious bunches of grapes on the hard surface with a messy splat I went back to hay for mulch. Seems like dropping ripe tree fruit might have similar damage problems? I use hay and leaves for mulching my young trees. When they’re older (bearing) I stop mulching and let the sod grow, mowing it now and then. I can appreciate what you’re saying about trying to keep a good enough layer of mulch around the trees to keep the weeds/grass down.
I’m not a fan of rocks or gravel after seeing a study where not one earth worm was discovered underneath. If you want a compact lifeless soil to grow plants in, it works fine.
I saw some research that suggested that gravel mulch and even gravel in the planting holes of fruit trees helps control voles/moles. I believe the research was originally done on ornamental and not fruit trees. I tried the gravel which did help to control the voles some compared to the untreated rows, but I only used it the first year. The downside is that the gravel damages your loppers when when you prune the unwanted root suckers out. I jerk most of mine out, but sometimes it takes a lopper to get the job done. I always use the same cheap lopper for that purpose and never put the good loppers in the dirt/gravel
I haven’t tried it just because they are heavy. The fact that they don’t improve the soil may be an advantage in the humid regions because lots of OM tends to reduce brix because it holds so much available water- but on the other hand, when water is scarce wood mulches serve as a reservoir as well as serving to deflect evaporation as all mulches do.
Actually I tend a small orchard in a courtyard where the trees (apples and one peach) are growing in boxes but most of the root systems are in the soil beneath a thick layer of white small stones. I’ve rarely added fertilizer to the soil except a little K (tests showed a deficiency) which I spread right onto the gravel. The walls and stones reflect light and improve the quality of the fruit, apparently. The Madison peaches there get higher quality than those on my own Madison- more sugar.
Some of the trees there have access to the lawn area but others don’t and I haven’t noticed any difference in fruit quality between them which suggests to me that the advantage comes mostly from reflected light. I’ve been managing them for 20+ years (through 3 different owners).
I recommend you use heavy landscape fabric underneath to be sure of near complete weed control.
Thanks for the replies, sounds like there’s some pro’s and con’s to rock. I guess I’ll stick with the wood or straw mulch.
I actually just got done with weeding and mulching (using straw) the last of my trees today. I had done the 3 apple and pear trees a couple weeks ago down by the barn, and did the 11 apple and 2 peach trees behind the pond this week.
Also had to redo the protection around all the trees, as they were getting outside the perimeter of the circular fencing around them. All the trees now have 4ft high welded wire fencing. Glad to be done with all that, that was a lot of work.
Over the next couple days I’m going to put new mulch and fencing around our pecan trees out in the pasture. It’s deer season, and I need to protect them from bucks rubbing on them. Stupid deer. They have almost cost me as much in protection costs as the trees themselves!
This might make some cringe, but I have used the rubber mulch rings for several years with no weeds breaking through. I tool a peak under one and it was full of worms. Go figure.
That’s very interesting. Why would worms proliferate under rubber? Has the rubber broken down any? Maybe the rubber allows more air and moisture to get down into the soil compared with rocks? I don’t know.
That’s good to know. I thought of using rubber to provide heat in the spring, like to watermelons, and other hard to grow crops here. Black plastic can be used too. Rubber btw, natural rubber is from the para rubber tree, so it’s organic.
It makes me cringe because I assume you are talking about shredded tires which leach a lot of chemicals I would be wary of adding to my soil. I installed an orchard in soil with poor drainage bordering a children’s play area where shredded tires were used and the water that drained onto the trees smelled terrible for a year (maybe it still does, it was very dry here this year). You can do a simple search to find out what chemicals I’m talking about and how they do leach from this material.
I tried a stone weed barrier for trees in my yard. The stone came from piles around the fields left by early farmers. I pulled out all the large round stones. There is only small stone and larger flat stone. I put the larger flat stone on top. I filled in a 6’ diameter ring that is at least 6" deep. I always check to make sure there is at least 1" gap between the stone and tree trunk.
Some weeds grow through, but are easily pulled or spot sprayed with Glyphosate. I measured the temperatures of stone during the first summer. It was like ceramic heat tiles on spacecraft. The upper layer was very hot, but layers beneath were cool enough that there was condensation on the stone. I can’t remember the numbers, but the temperature differential was more extreme than I expected.
Several sources talk about using pea gravel (3/8" size) for a foot around the trunk to keep voles away. But it seems that it is not recommended beyond that.
In addition to what Richard mentioned about hot climates, in cold climates, rock mulches tend to drive the frost down deeper into the soil.
Do you have any reason to believe the trees don’t compensate by rooting more deeply? Any research that suggests this is a real threat to the survival of trees? Here’s a quote from a cooperative extension bulletin on using rocks, “Rock mulch absorbs heat during the day and releases the heat at night thus increasing water loss. Avoid using rock mulch around plants that might not grow well under these conditions”. Not that I necessarily believe it.
I believe the pea gravel is not recommended beyond that is because that is the amount needed to discourage vols, not that more is detrimental.
After a long search I really can’t find much about using gravel or small rocks as mulch. .
I have an ~30" diameter ring of peastone mulch several inches deep around my new trees. Beyond this I’ve sheet mulched with cardboard, spoiled hay and woodchips. The gravels works quite well to suppress weeds, retain moisture, allow for borer inspection, and secure wire mesh rodent guards. I will definitely use it in future plantings.
Alan. My source is Bill, the previous owner of St Lawrence Nurseries, who used to (maybe still does) state that stone mulch tends to deepen frost around trees.
Much of how the heat balance for stone mulches work out has to due with variables such as how bare the ground/mulch remains, how windy the site is, and how much sun falls on the ground. I’d expect that there is enough variation that a blanket statement that applies everywhere is not going to be valid for everyone. Still I think that for colder climates (such as St Larwrence’s locale), this is likely good advise.
Not sure if the tree would compensate by growing its roots deeper, at least over the long run. But certainly for the first year or two after planting, the tree likely can’t compensate quickly enough (how would it “know” that the frost is going especially deep before the first winter or two). And even if it did, is that sufficient to compensate?
I have seen how leaves and rotting wood in the forest prevents freeze from even reaching soil on a normal winter in Zone 5-6 and observed fresh white root in the humus layer just below the unrotted leaves in mid-winter forest soil, where nearby soil with mowed lawn is frozen solid- so I would agree that an organic mulch that insulates will insulate better than bare earth, mowed sod or stones. Still, I believe that most commercial orchardists, even in very cold areas, actually start with whips in bare soil with no insulation but soil. In these areas, bare root transplanting is discouraged in fall but succeeds in spring. I don’t really know how much difference there is between bare soil and stone and Bill may or may not be correct, or even asserting that small stones or gravel are less insulating than bare soil.
I do try to help keep this forum limited to the personal anecdotes of members and not having it cluttered with recirculated 2nd person anecdotes because that can lead to a confusion of misinformation mixed with actual info. At least with first person observations we have the opportunity to ask follow up questions.
In this case, I think we’ve accomplished that anyway. Thanks for clearing the matter up. . .
