Mulching

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Alisdair

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Re: Mulching
« Reply #30 on: July 01, 2012, 12:54:28 PM »
Those notes on your own practical experience are really helpful, Alice; thanks!
To answer your second question, a thick layer of bone-dry organic material will certainly increase the fire risk. Research on wildfires in the last few decades has shown that the more fuel there is, the more frequent the incidence of fires. (This explains an odd paradox: in regions where wildfires are part of the natural regrowth cycle, fires tend to occur every five years or so in the higher-rainfall more fertile areas, instead of only every 25 years or so in the drier and more parched areas - even though one would intuitively expect these more parched areas to be more at risk from fire.) Also, the more fuel there is, the more intense any fire will be.
On the first question, yes, there's no reason why winter rain shouldn't get through to the earth below the mulch.
Alisdair Aird
Gardens in SE England (Sussex); also coastal Southern Greece, and (in a very small way) South West France; MGS member (and former president); vice chairman RHS Lily Group, past chairman Cyclamen Society

Alice

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Re: Mulching
« Reply #31 on: July 03, 2012, 07:08:30 PM »
Thanks for the information, Alisdair. One learns something every day.
Amateur gardener who has gardened in north London and now gardens part of the year on the Cycladic island of Paros. Conditions: coastal, windy, annual rainfall 350mm, temp 0-35 degrees C.

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Marilyn

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Re: Mulching
« Reply #32 on: July 04, 2012, 06:00:52 PM »
Hi all, I have been re-reading this topic with interest - I actually thought I had replied before, but perhaps I held back, feeling shy after so much anti-organic mulch debate (we use mostly composted or shredded garden waste).

For what it is worth, my experience agrees broadly with Fleur's comments about gravel vs. organic mulches. We are fortunate here to have a large area and lots of vegetable mass to play with (some parts are irrigated and growing in the summer and we still have lawns, much though I would like to dispense with those). The more woody material gets shredded before going on the compost heap, while lighter weeds, hay and grass clippings going straight there. The material does not always have a chance to break down very thoroughly, partly because we don't water the heap as often as we should, but it gets there in the end, and even if it is semi-green when it goes on the soil it does not seem to do any harm.  

One exception is oleander cuttings - I have heard it said that these can poison the soil, but I could not tell you that they have definitely had an effect on plants in the garden here, where they have always been mixed in with large quantities of other material. I would be interested to know others' views and experience of this, or other plants to avoid putting back into the ground.

When I can get it, I bung a good load of manure on – but this is in the exotic garden; we try not to alter the natural soil conditions in the native plant zones, tough though they may be for young establishing plants. It is worth reiterating I keep all mulches away from the collar of the plants, be they sub-tropics or mediterraneans; but as Fleur has mentioned, nothing really stays wet for long enough to pose a problem.

In terms of benefits, I would highlight improving soil texture, supressing weeds and making them easier to pull out in future, and moisture retention. We have somewhat varied soil, in places very compacted, others extremely sandy, others almost pure clay, and the mulch helps in all of these situations.

One perspective that goes slightly against the gravel/garrigue argument is that an organic mulch imitates nature - fallen leaves are caught at the twiggy base of a plant in the wild, whereupon they do all the good stuff an organic mulch should.

I have also used gravel around culinary herbs and the like, and of course it has its benefits too, especially in pots, where a free-draining surface is useful. The other application where I would really recommend gravel/mineral mulch over organic is cacti and succulents - I have seen these improve literally overnight with the addition of a couple of inches of free-draining top dressing.  

Hope that helps and please keep adding your views, it really is interesting and useful to compare notes.
I work in hotel and private gardens, promoting sustainable landscape management in the mediterranean climate through the use of diverse, beautiful and appropriate plants. At home, I garden on two balconies containing mostly succulents.

David Bracey

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Re: Mulching
« Reply #33 on: July 05, 2012, 08:41:56 PM »
Are we trying too hard with our mulches??  Various members have written to say that structure is improved as well as  water retention, ferility and so forth.  Surely the point is that mediterranean plants have evolved to grow in "thin", well drained soils, with a relatively high pH  and here we go trying to make the enviroment "better" like Victorian gardeners.  Why not grow  lawns?

Just a thought.

MGS member.

 I have gardened in sub-tropical Florida, maritime UK, continental Europe and the Mediterranean basin, France. Of the 4 I have found that the most difficult climate for gardening is the latter.

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MikeHardman

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Re: Mulching
« Reply #34 on: July 05, 2012, 09:54:04 PM »
There's certainly a case for what you say, David.

But I do think broad opinions on 'mulch' as a whole are complicated by the fact that the word 'mulch' can be used for different purposes, and maybe a single mulch can be used for more than one purpose at a time (eg. weed suppression and aesthetics).

By analogy, if we just had the word 'fruit', it would be no surprise that there was no consensus on how to grow 'fruit'. Thankfully, we have recognized different fruit and given them different names. That helps a lot.

We can use phrases to differentiate mulches, eg. gravel mulch, humic mulch, plastic mulch. That's good because it is a flexible system in which the terms are easily understood. But humans like shortcuts, and sometimes such phrases are too much trouble! Perhaps new words could be coined: eg. grulch, humulch, plulch?  No, OK. 'tis late and my thoughts are wandering!
Mike
Geologist by Uni training, IT consultant, Referee for Viola for Botanical Society of the British Isles, commissioned author and photographer on Viola for RHS (Enc. of Perennials, The Garden, The Plantsman).
I garden near Polis, Cyprus, 100m alt., on marl, but have gardened mainly in S.England

Umbrian

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Re: Mulching
« Reply #35 on: July 06, 2012, 06:28:34 AM »
Very good point David re mulches and I suppose the reason many people use them to improve the soil and conditions is that they want to grow things that are not entirely happy in Mediterranean climates. People who are hooked on gardening are not content to grow only things that are well adapted and will survive whatever the conditions, survive being the operative word because at times the resulting garden will not be particularly attractive.  ???
MGS member living and gardening in Umbria, Italy for past 19 years. Recently moved from my original house and now planning and planting a new small garden.

Alice

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Re: Mulching
« Reply #36 on: July 07, 2012, 10:31:40 AM »
I understand that many of the barren areas around the Mediterranean were once covered in forests and that human activity (deforestation, domestic animal grazing, fires etc) and the resulting erosion led to the current thin, poor soils, in other words what we now see is a degraded habitat. Organic mulching is just giving nature a helping hand, imitating something that would happen naturally but would take decades or even centuries of no human interference.
In our garden, since we started mulching, we are seeing a build-up of topsoil and a vastly increased number of soil insects and earthworms, which in turn are bringing in more hedgehogs, lizards and birds, in other words an explosion of life.
Amateur gardener who has gardened in north London and now gardens part of the year on the Cycladic island of Paros. Conditions: coastal, windy, annual rainfall 350mm, temp 0-35 degrees C.

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ritamax

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Re: Mulching
« Reply #37 on: July 07, 2012, 05:28:58 PM »
I suppose a lot has to do with our gardening habits, the choice of plants and the general life situation. If one gardens in the English way with lots of different plants very near each other, organic mulching comes logically. If you are an absentee gardener as I am, mineral mulch with a geotextile underneath (stone chippings or gravel over it) with only drought-tolerant plants is the most low-maintenance. Looks neat and you have practically no weeds, there have been no fungal diseases or other pests so far. If one chooses a light colour for the mineral mulch, it reflects the sun and the soil does not get overly heated (that is my experience), the moisture retention is good. After getting used to this comfortable way of gardening I am mulching now in Basel with lava rock and it is fantastic - no slugs, less fungal problems, good moisture retention. It would be useful to exchange, which plants like/dislike organic/mineral mulch. 
Hobbygardener (MGS member) with a rooftop garden in Basel and a garden on heavy clay with sand 600m from seaside in Costa Blanca South (precipitation 300mm), learning to garden waterwise

David Bracey

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Re: Mulching
« Reply #38 on: July 08, 2012, 10:35:06 AM »
Alice please read "The Nature of Med. Europe " by Grove and Rackham where they rebut the idea of desertification and erroded landscapes arguing that the Mediterranean is a natural landscape caused over time by climate changes.
MGS member.

 I have gardened in sub-tropical Florida, maritime UK, continental Europe and the Mediterranean basin, France. Of the 4 I have found that the most difficult climate for gardening is the latter.

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JTh

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Re: Mulching
« Reply #39 on: July 08, 2012, 05:19:26 PM »
Almost everything I have planted in my garden in Greece has been drought-tolerant plants, but it has been an uphill fight ever since the beginning, the soil is poor, clayey and with lots of rocks; when it dries, it is so compact that digging is almost impossible.  Clearly a bit of mulching and soil improvement under these circumstances can’t be wrong?

I have a Campsis I planted more than ten years ago (don’t know which species, it was not named properly), it has barely survived and is now almost one m tall! no flowers yet.  I am certainly not trying to make an English garden (or a Norwegian one), but it would be nice to see something besides dried, brown weeds around the house. Fortunately, all the rain last winter help, it actually looks better this summer than before.
Retired veterinary surgeon by training with a PhD in parasitology,  but worked as a virologist since 1992.
Member of the MGS  since 2004. Gardening in Oslo and to a limited extent in Halkidiki, Greece.

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ritamax

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Re: Mulching
« Reply #40 on: July 08, 2012, 07:10:46 PM »
I have the same kind of compacted soil in Costa Blanca. Olivier Filippi, Linda Chalker-Scott and others say, that one should not make soil amendments with organic matter in the plant hole, but one should take care of the drainage and to mulch well. Linda Chalker-Scott warns putting organic matter in the plant hole, because the roots will not fight their way through the original soil, but go around the plant hole, where the water will then sit. The plant hole might later sink down. She also says, that there should be only 5-10% of organic matter in the soil and that most gardens have much too many nutrients in the soil because of the constant soil amendment and of course too much fertilizing. Linda Chalker-Scott is very convincing in her arguments and contradicts many common gardening beliefs.
Hobbygardener (MGS member) with a rooftop garden in Basel and a garden on heavy clay with sand 600m from seaside in Costa Blanca South (precipitation 300mm), learning to garden waterwise

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Fleur Pavlidis

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Re: Mulching
« Reply #41 on: July 11, 2012, 09:15:12 PM »
Absolutely, Jorun, we're making gardens which by their very nature are unnatural! For instance, I want to grow my plants much more densely than they would chose to be on the local mountian, so of course I adjust the growing medium to take account of that by using mulch and mixing compost into the planting holes. My plants never grow too lushly - the humus added seems to disappear quite quickly, I assume because of the heat. However I have found that once the plants have grown to make a complete ground cover, the natural leaf drop takes over the job of mulching and I don't have to bother any more.
MGS member, Greece. I garden in Attica, Greece and Mt Goulinas (450m) Central Greece

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JTh

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Re: Mulching
« Reply #42 on: July 18, 2012, 07:27:06 PM »
I agree with you, Fleur, I have made the same observations, when the plants have finally reached the stage where they produce their own mulch, then they are fine, but it my take several years, so why not help them a little bit in the beginning?
Retired veterinary surgeon by training with a PhD in parasitology,  but worked as a virologist since 1992.
Member of the MGS  since 2004. Gardening in Oslo and to a limited extent in Halkidiki, Greece.

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Fleur Pavlidis

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Re: Mulching
« Reply #43 on: July 19, 2012, 09:59:26 AM »
Also there’s this business of “10 cm” of mulch as a requirement which can get you despairing before you start. I’m afraid I believe it’s another case of one author writing it and all the others just copying in blind faith. Anyway that’s my excuse for ignoring the instruction and feeling very content with a good layer of 3 - 4 cm. 
MGS member, Greece. I garden in Attica, Greece and Mt Goulinas (450m) Central Greece

Alice

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Re: Mulching
« Reply #44 on: July 19, 2012, 01:11:14 PM »
I think a 10cm depth of mulch is required to make any significant difference to water needs at the height of summer. But, of course, any amount of mulch is good and its benefits are many besides reduced water requirements.
I also find it most satisfactory when plants produce their own mulch; but, as we are placing them suddenly in a relatively hostile environment, why indeed not give them a helping hand?

To take up Marilyn's point regarding possible poisoning of the soil by Nerium oleander cuttings, I have two questions:
1. Some plants (e.g. Eucalyptus, I believe) are supposed to exude certain chemicals which discourage the growth of other plants in their vicinity. Would mulch from such plants retard growth where applied?
2. Can plants take up poisons from mulch obtained from highly toxic plants, such as Nerium oleander? If so, would that make edible crops dangerous for consumption?
Amateur gardener who has gardened in north London and now gardens part of the year on the Cycladic island of Paros. Conditions: coastal, windy, annual rainfall 350mm, temp 0-35 degrees C.