Mulch Q's for Mediterranean Climate

John Polk wrote:I think that mulching practices need to be tailored to the site.
The fine tuning of the system may take a couple of years to find the best solution for each site.
Soil types and weather patterns will greatly effect what works best.
Some trial and error tests would be needed to find a 'happy medium'.
And once you have found the right combination, don't forget: next years weather may be far from normal...oh, well.

For example, in an area where you typically get 1/4 inch of rain per event, and have 4 inches of mulch, it is unlikely that any of that rain will ever reach the soil. The top 1/2 inch of mulch will get damp, and most of that moisture will evaporate off in a warm, arid region. It would be labor intensive to go out and rake the mulch away from the plants just prior to each event, and then push it back into place after the rain stops. In a smallish garden, that practice could maximize the use of rain, but would be impractical on a large site.

Letting your mulch decompose on the surface works well in humid environments, but can be counter productive in an arid region. In an arid region (or season), I think that it would be more productive to mulch with finished (or almost finished) compost. It is much quicker to compost in large piles than it is in thin layers. Finished compost will turn dirt into soil much quicker than raw vegetation will.

For most arid regions with a Mediterranean climate, I think that the optimal time to mulch is in the autumn. This gives the mulch the opportunity to collect a maximum of autumn rains and winter snows, and ample time to weather before the spring rains cease.



So I can use compost like mulch? Lay it on bare soil as a protective covering? Won't it dry out quicker than mulch, and be pretty much just dirt on dirt?

Aljaz Plankl wrote:Depends on mulch you're going to use.
You can forget about hay, it will draw more moisture out of soil and keep all the rainwater for itself.
This are my experiences using only hay without additional watering or organic matter.
You need as much fresh stuff as possible for mulching, manures are excelent.
What really works here in Slovenia in sub-meditaranean climate region is no-dig soil mulched 10-20cm with one year old goat manure (straw bedding) in fall.
No dig is essential i think, as capilary action is not damaged.
Also, when diging you introduce too much air, making soil even more dry.
Even if you incoirporate organic matter, soil uses it too quickly because all life needs to reastablish.

Alder Burns wrote:The longer I live and garden here in the northern Central Vally (CA) the less and less enamored I'm becoming of mulch as the panacea for every need of the garden. At least combined with irrigation (and I will always have to irrigate here if I want any summer crops or anything other than, say, acorns and olives and such like), mulch quickly becomes a habitat for large numbers of earwigs, pillbugs, and, if damp enough, slugs. If I bury my drip tape or soaker hoses in the mulch, it's much more likely that rodents will chew holes in it. A permanent wood-chip mulch or some such around permanent plants is working, but such plants are usually up out of the reach of the ground bugs and have the heavier, emitter hoses. But for annuals I'm stepping back to bare soil and hoeing, which also seems to be the best way to keep the cursed bermuda grass in check
I've tried to subdue this with cardboard sheet mulch, but two years plus under a solid cover isn't sufficient yet.....I'm just going to keep at it in this one area, re-doing it in patches where I see it coming through; but I definitely can't plant anything in there or the grass will be back through the gaps where I insert any plants through.
My hunch is that the Mediterranean ecosystem is just different, and perhaps lower in diversity than the Eastern, summer moisture places I've lived before. When and where I irrigate, aggressive pest species rapidly proliferate, and their predators, parasites, fungi, etc. that might keep them in check elsewhere aren't present here yet. Several sources recommend poultry rotated through garden areas....which I can see working, though it requires more fencing and infrastructure than I have yet, and also ducks, basically free ranging except where very small plants are present...they have more appetite for bugs and less for plants than chickens do, and they do not scratch like chickens do, and their bills fiddle through the mulch seeking out the bugs. Odd thing that a wetland bird should be a good solution for a dryland garden.....I have them on the one/two year plan!

So I can use compost like mulch? Lay it on bare soil as a protective covering? Won't it dry out quicker than mulch, and be pretty much just dirt on dirt?

John Polk wrote:

So I can use compost like mulch? Lay it on bare soil as a protective covering? Won't it dry out quicker than mulch, and be pretty much just dirt on dirt?

To me, this is one of those 'iffy' situations. Compost can be a great mulch. Most compost is basically dead plant material that has most of the water out of it through the composting process. Yes, since it is drier than 'fresh' plant material, it will absorb more of the rain (and irrigation water). In the wrong situation, that means most rain that falls on it, will end up being evaporated into the atmosphere (during the dry months). A light covering of 'regular' mulch will help mitigate that problem.

I grew up in SoCal, but spent most of my time in 4 different parts of L.A. county. Each of those areas had entirely different climates. What would work to perfection in one zone, would be totally worthless in any of the other three. Two of those parts were less than a mile apart, as the crow flies, but the differences were extreme. I also spent a couple of years in the Middle East. What worked best there, was almost exactly the same as one of those areas, but would not work well in the other three. That is why I stated that each solution must be tailored to the site.

Whether it is compost or mulch, it isn't (yet) part of the soil. Eventually, it will become a part of the soil, but in the mean time, it is acting as a protective layer, a buffer zone - an important 'edge'.

Tree leaves (especially from natives) can make a very good mulch for plants. For most of us, our first choices will be things that are in abundance, at no cost. Free leaves (or grass clippings) will almost always 'trump' a bag of xyz purchased at the local garden shop. Use what is readily available to you. Whatever it is, it is a step above bare dirt.

I've been mixing the mulch in with a pitchfork as of late because I don't think we have enough things living in the soil to help break them down for us.

John Polk wrote:

I've been mixing the mulch in with a pitchfork as of late because I don't think we have enough things living in the soil to help break them down for us.

Any time that you mix organic matter into the soil, you are providing food for the soil 'critters'. Dirt has no life. Soil is teeming with life - the 'Soil Food Web" (SFW). As the food supply increases, the critters will begin multiplying - to the point that there is insufficient food, at which point the critter's population will begin decreasing. Adding organic matter to the soil is the simplest way to add microbial life to the soil.

John Polk wrote:I don't see the harm in using a pitch fork, or broad fork.
I have heard claims that it admits too much oxygen into the soil, but I do not think that is even an issue.
Soil needs approximately 25% of its space occupied by water and air.
Most soils I have dealt with could use more water and air than they have.

A hand operated pitch fork is not going to have any significant impact on the soil life.
If it is delivering food to the soil life it is having a positive effect.

Something like a rototiller, on the other hand, can be devestating to the soil life.
Multiple blades, spinning at 600 RPM, don't give living creatures much of a chance.
We all know that worms move slowly - certainly not quick enough to outrun a 600 RPM steel blade.
Most of the soil food web is much slower than a worm. Some of those critters probably move less than an inch in their lifetimes.
Two minutes with a rototiller will probably kill more critters than an 8 hour day with a pitch fork.

I've been having some success with this method, but is it destructive of the soil?