[ezeiza]

I have been reading all postings and nobody seems to mention this most important topic in dry summer gardening, mulching.

Why is it not more widely used I wonder?

[MikeHardman]

I agree - mulching is an important subject.

It has been mentioned here before:
- carob fruit (http://www.mgsforum.org/smf/index.php?topic=186.0)
- and a passing mention (http://www.mgsforum.org/smf/index.php?topic=247.0)

But there is much to discuss...

Reasons for using (or not) - weed control, ease of maintenance (maybe), cosmetics, design element, moisture control, control of reflected light, etc.

Material:
- Organic - wood chips, shredded prunings, pine needles, etc.
- Inorganic - gravel/pebbles (different colours, rock types, acid/basic reaction, particle size and shape), impermeable plastic (translucent and black types), permeable membrane (eg. 'Mypex'), old carpet, etc.

Irrigation issues - harder to know that supplied water is going where intended, including rain water. If mulch diverts winter rains from the soil, the water table can recede, leaving plants vulnerable the following summer(s). And diverted storm water can cause erosion problems elsewhere.

Rooting issues - mulching can encourage plants to root near the surface, making them less drought resistant and less secure in the wind.

Cultivation issues - can be much more difficult to transplant, know how healthy a plant is (harder to inspect the soil for root-chewing pests, eg.), apply fertilizer, etc.

Cosmetic issues - coloured gravels (please, no!), Japanese Zen garden (gravel raked into patterns, etc.), white gravel can cause too much glare in the sun but can also reflect light into dark corners.

Costs

Supply - where to obtain mulch (which may be an ongoing requirement, if the type of mulch is one that degrades)
[David: thanks for this addition (update 4sep11)]

Maintenance and longevity - some man-made mulching materials degrade in sunlight, gravels can clog with leaves and soil, organic materials decompose (and may harbour pathogens), how best to dispose of old mulch.

Methods of installation - ground preparation, irrigation below or above, piercing impermeable sheets or not, overlapping joins


...Those are just some of the issues that come to mind immediately.
Please suggest others...

[ezeiza]

For a mediterranean type climate I was thinking of a clear shredded wood mulch applied in spring, not a permanent one.

[David Bracey]

To mulch or not to mulch, that is the question............and what with.? In the Languedoc I would mulch with what ever organic matter I had that had well rotted down.  The problem then is that the mulch is rapidly photodecomposed and you have to start again next season and rotted organic matter is hard to come by.  I then turned to pine bark chips which worked very well and lasts for several seasons. It makes a very good medium to walk on and sets the garden off.

Thus SUPPLY (and cost) is an issue omitted by Mike.  I remember a Californian member saying that they would go to the local  municpality and buy a truck-load of worked-compost and layer it on------------I think she said to several inches thick which sounds wonderful.  Our local council produces the stuff but it is not available to the amateur gardener, I expect it will be one day.

I think I prefer mineral mulches since they never breakdown and offer most of the advantages however gravel and stones all take some finding, collecting and spreading. In the garrigue there is generally a covering of small stones and gravel.

The hunt for peat compost alternatives goes on and there is a lot of research looking at mixtures of grape marc, tomato soup waste and cattle manure, maybe this is the future.

I received a note from an MGS member in South Africa which said that gardeners there were having problems growing certain Ericas, Proteas and Heliophilis in Fynbos soils due to the possible build up of soil diseases such as Phytopthora. Soil-borne diseases kill lavender, rosemary every year.

I think you have to pay you money and take your pick.  There is no right or wrong, its what works for you.  David

[JTh]

I would be happy if I could get hold of any organic mulching material, but so far I have not been able to find anything at all where we are in Halkidiki (northern Greece). I don't mind if I have to apply new material every year, it would certainly improve the soil we have tremendously. I bought 3 m² of the best soil I could find last month, but it seems to have very little organic material. Fortunately, I had some partly decomposed compost I could apply on top of the soil which i hope will be an improvement.
We have talked about buying a shredder in Greece as well, we have one in Norway which we use all the time, and we produce huge amounts of very good soil here, more than we can use ourselves, so we give away a lot to our (lazy) neighbours. What is your experience from the mediterranean climate?

[Fleur Pavlidis]

The MGS has a useful beginners' leaflet on the subject reproduced as a word file here.
I garden in Attica which is rather like Cyprus in terms of poor soil and summer drought; also I imagine in the non-availability of organic mulch commercially. On two occasions I got a lorry-load of cotton waste delivered which made a wonderful black mulch once it had rotted but it smelt awful in the meantime. A material with a lovely smell and appearance was cocoa waste but the supply was cut off. Of course any organic mulch need renewing every year which is really the point because the mulch is improving the soil at the same time as protecting it. Unfortunately if I can’t find an outside source I find it impossible to keep up mulching with material only from the garden. I shred all the prunings I make which isn’t diseased but from a mountain of stuff you get a few square metres of thickly laid mulch, so then you have to decide who deserves it. I try always to mulch new plantings, keeping the material away from the planting hole. Then I look for places where the previous mulch has disappeared. I think that protecting the soil from the sun and wind is more important than conserving moisture. After the first few weeks of the summer there isn’t any moisture left in the top soil anyway. I choose not to use inorganic mulch.

[David Bracey]

That`s the problem , getting hold of O.M.  I used everything from vegetable wastes, soft and hardwood prunings cut down to 5-10cm lengths,old flowers, grass clippings etc.  The compost heap also received lots of rain run-off so it was always moist.

I also spread ammonium nitrate (?) on it to provide nutrients for bacterial breakdown and also to encourage worms. I have never brought in soil.  I think you have to work with what you have, make local adaptations and be ruthless in what is successful and what is not.

Fleur why do you not use inorganic mulches?  David

[MikeHardman]

I favour inorganic types of mulch (albeit based on limited personal experience).

Thanks very much for that Word doc, Fleur.

Some themes seem to be emerging:

- supply is a problem (available but costly gravel and/or geotextile; industrial or agricultural organic wastes such as cotton can have problems such as smell; insufficient volume of indigenous plant material for shreddings; etc.)

- need to experiment and see what works (which may vary from place to place within one garden)

- need to consider the soil ecosystem (naturally inorganic soils can be upset by the addition of organic material, leading to fungal diseases, and plants' increased susceptibility to them, eg.)

Dear departed Geoffrey Smith used to describe good compost as being 'good enough to smoke'. I liked that, and thoroughly agreed (in principle). I am trying to teach myself to accept that a good growing medium in the Med. is, for many native plants, something different. Here, I don't expect to find earthworms when I dig (nor to be accompanied by a robin with similar expectations, more's the pity). For gardeners from cool temperate climes, it takes some getting used to.
(For non-UK folks: Geoffrey was a well respected gardener on British TV.)

[ezeiza]

While the use of gravel, grit, etc. in Norway or Scotland would be fine, it will cause an overheating problem in full sun in a warm climate.

Sewage sludge, or stable manure would be choices for quantity, granted it is difficult to find them. What about shredded leaves: they must be available in quantities.

A powerful shredder is the best possible investment. Shredded material will occupy a lot less space, decompose faster and the wind will not carry it away.

Since we can not dispose of the very large quantities of autumn leaves for the compost heaps, we just dig them in the ground in beds. By the book this would be wrong but in practice they decompose in a couple of months and the soil becomes very grainy and porous. No signs of any nutrient shortage although admittedly our soils are naturally rich.

[pamela]

Has anyone used Gypsum?  I have been reading its good for dealing with Phytopthera because it conditions clay soils.  I am not really sure about using it regardng safety etc. 

[Daisy]

I have been using aged donkey manure as a mulch, especially around all the greedy guts. i.e. roses and clematis.
However, I have found that it doesn't disappear. In fact, it looks just the same now, as it did fifteen to eighteen months ago when I first put it on!
Daisy

[JTh]

Both horse and donkey manure have a large amount of fibrous material which will not decompose rapidly if the conditions are dry

[MikeHardman]

Pamela,
Re gypsum: Interesting point. There seems to be a lot of information/misinformation about. This sums it up somewhat - http://www.puyallup.wsu.edu/~linda%20chalker-scott/horticultural%20myths_files/Myths/Gypsum.pdf.
Its use in helping control Phytopthora seems to be reliable information: I just wonder about dosages, in non-agricultural situations.

[John J]

I suffer the usual problems when it comes to composting (ie finding the correct balance between heat and moisture) and mulching, finding sources of sufficient quantities of OM without having to pay large amounts for it. So when I find plants that don't need to be cossetted and literally thrive in poor soil they're worth their weight in gold. My daughter and son-in-law built a house on a slope and part of the property has a 2 metre retaining wall. On top of this wall is a narrow planting strip that was backfilled with all the sub-soil and debris from the foundations etc. I did nothing to improve this 'soil' but planted into it such things as; Eriocephalus africanus, Euphorbia veneris, Chrysanthemoides incana, Eremophila maculata and Asteriscus maritimus. The photos show the results a few years later. All the plants have performed 100% better than the same plants in my flat field with the reasonably fertile soil. The only thing they have going for them is excellent drainage when it does rain!

[MikeHardman]

V. useful comments John - more notes made - thanks