Yes mulch can prevent rain water from getting into the soil. It should only be about 2 inches deep.

Very finely ground mulch is particularly bad about forming a watertight barrier. I lost a group of valuable roses that way when we lived in Texas.

I think mulching is a gardening myth waiting to be debunked. I never ever mulch rose beds in my garden for a number of reasons including in particular the barrier to rain getting into the soil.

Like anything in the garden, there are so many variables.

Like the source of your water for irrigation, if it is rain, then you want to make sure your mulch will allow it to penetrate. If like us you are using a drip system under the mulch, the rain is going to hit the top of the mulch and in the zone around the rose canes where we do not mulch.

Not all mulches are the same either. Right now we are using layers of coastal oak leaves, very different from other kinds of oaks because the leaves are cushioned shaped with little spikes to keep them from laying too flat.

johnnidappl, you don't give your gardening zone so I don't know how much rain your roses receive, but in my very hot and dry garden where there is no rain for at least six months of the year, I'd have to water my roses every single day just to keep them alive, never mind having them bloom, if they weren't mulched. The mulch also enriches my soil when it breaks down, which is helpful since decomposed granite doesn't encourage lush growth. I would imagine that in almost any zone a weed barrier like mulch would save a lot of work. However, I do agree that a layer that's too thick can spell trouble, especially if the ground hasn't been thoroughly watered beforehand. I've had the same experience as ilovemyroses with individual plants, and it's a downer. I just recently put down a layer of mulch and handwatered thoroughly before applying it. Like almost everything else in gardening, every situation is different and each gardener has to make his own decisions about what works best in his particular environment.

We are in a classic Mediterranean climate here in the No SF Bay (lots of rain Nov - March, none at all May - Oct). We mulch our garden in the Spring, to help it survive the hot completely dry 6 month drought., mostly with compost my DH makes every year from the huge amount of oak leaves we get from our 2 Scarlet oaks. The soaker hoses for irrigation are under the mulch. By the time the rains come in the Fall/WInter, the mulch has disappeared into the soil, and we don't renew it until the next Spring, so we don't have the problem of it keeping out the rain.

It sounds as if mulching, like everything else, is a function of where you are and what climate you are in.

Jackie

I never use mulch either. I don't like the way it looks, it's always messy, and it's expensive and has to be replenished all the time. Besides that I tend to garden barefoot a lot and I can't walk on it comfortably. The only time I tried it in a bed it was a complete wash out, literally, it floated away down the street in the rain.

I much prefer leaves to bark, and that's all I've used until this last application, but unfortunately I don't have a source such as Jackie has, so it's never been enough. We have lots of pepper trees but it's been mentioned here that they're not good to use for mulch.

We had a friend who had a tree trimming business who needed a place to dump wood chips. We let him dump them in the sandy areas of our pastures that had no grass whatsoever, and I raked it out smooth. After seeing the improvement of the soil in those areas and the regrowth of grass, I am a strong believer in mulch.

I also put lots of that mulch in my flower beds. The richness of the soil after the mulch rotted was amazing. I also top dress with horse manure. Perhaps if you don't garden in sand, it doesn't help that much, but it certainly does here.

I'm with you floridarosez9, last week the tree-trimmer dumped a truck-load of chipped water-oak in my driveway and I did a victory dance!! abt. 4 sq. yards, and half of it is already spread out and about....manna from heaven !! sally

If I didn't have mulch, my 'soil' would turn to concrete being baked in the hot sun. Mulch isn't a myth, it works well in many circumstances.

Shallow-rooted weeds make good soil cover, too. Just kidding...sort of. Successful mulching does seem to vary by ecosystem. Thank you, ilovemyroses, for noting that one can have too much mulch. Some gardening resources fail to mention that fact. They imply that more is merrier. Like Jackie, I mulch to survive the drought summers. I do mulch in the fall, using every smallish semi-disintegrating leaf from every tree within a block radius. I "kindly" offer to rake my neighbors' walks and curbs to collect material. Portland charges homeowners when its city crews perform these tasks, so I am simultaneously winning friends in the process. I throw (literally) the leaves on my beds and either the rains are heavy enough to penetrate or the leaves don't create much of a water barrier. By spring, the leaves look more like (free) mulch than soggy dead foliage. Like Ingrid, I've noticed that the mulch eventually becomes a soil component. Sometimes it's just swallowed by the clay, failing to alter the composition but tinting the red clay an interesting shade of gray. Before I mulch again the next fall, I half-heartedly trowel any remaining recognizable leaf material from the previous year into the ground. seil, I don't know whether this will be a helpful tip for you, but I have gardened in situations where the carefully applied mulch (in my case leaves) merely floated away in spring showers as yours did. When I added some of my homemade compost to the mix, the leaf mulch became a weightier substance and it remained in place. Rainwater still reached the soil. Mulching in the spring--post major showers in many places--as Jackie does sounds promising, too. As you've gleaned, I'm not a very scientific gardener. I research a little, experiment a lot, and watch to see what happens. ilovemy roses, I'm sending recovery thoughts for your Austins. At least they're surviving your tempestuous spring storms!

Carol

On a cold or frosty night, blankets up high is my general rule, while nestled in my bed. But I generally leave a few inches uncovered for breathing.

Oh, wait, we're talking about roses and mulch.

But it's kinda the same ...leave room at the base of plants for air and water to get in. It's not just the height of the mulch, but how close it is around the trunks as well.

I try to use manure or compost around all of my plants. For the beds I'm growing berries or apples with nothing in the between spaces, I mulch heavily with leaves, chipped wood, whatever is free or easily obtained.

For beds where there are a lot of perennials or undergrowth plants, I generally only use manure or compost around the plants. I look at the oxalis and violets as a mulch in itself; I think they help my roses, and they keep out other weedy things from taking over. They are aggressive, but easily controlled. But I don't have the evil oxalis that plagues some of us.

This post was edited by harborrose on Mon, May 27, 13 at 23:38

Our year-to-date rainfall is 8 inches. Without mulch I would have cement hard, parched, cracked soil--talk about ugly. I do have to make sure the irrigation (whether it is watering can, hose, drip or soaker hose) goes beneath the mulch.

Anne

Yes, you can have too thick a layer of mulch. You can poison yourself overdosing on Vitamin A or iron supplements, too. The right measure is essential.
I amend my beds with composted mulch, afterwards fertilize only with mulch and with the little plants I let grow in the beds, and with plant trimmings, and it works just fine. Carol, weeds ARE mulch! If they're pretty and noninvasive, they're native volunteers and are welcome to stay; in fact they become part of the ornamental design.
I made the same discovery as ilovemyroses about hay: it packs down and doesn't let water through. I lay it down more thinly now and break it up where it's matted, and the garden is a lot happier.
Melissa

It's interesting to read everyone's opinions about and application of: mulch. I can understand johnnidappl's opinion about mulch not being necessary... in situations where rainfall is adequate and the soil a bit retentive and in good condition. Although our soils must be so different, I am a lot like Florida Rose in that I love mulch for what it does for my soil when it breaks down. I am always starting new flowers beds, way before I have mastered existing ones unfortunately, and I like to mulch the first season once summer really begins. My own main purpose is to try, oh my gosh TRY, to keep the weeds at bay. But in the end I am not a big mulcher because I want my annuals and biennials to re-seed. So after that initial mulch, I won't do it again but will add a layer of compost or manure or peat moss in the fall when it's time to sprinkle poppy seeds or other seeds that benefit from the cold weather. The next year the weeds are not gone but are usually manageable and the plants thick enough that the soil is not exposed to the baking sun.

I should have mentioned that my garden is in South Australia where the summer temperatures are very high and we have little useful rainfall from October through to late March. I just make sure the roses are well watered which is pretty much every single evening in the summer.

And there I get to what I believe is another myth - that you shouldn't water overnight and get the leaves wet. If the roses are disease resistant, I don't think it makes any difference.

I think it is more that the foliage needs to dry within about 12, or is it 24 hours, rather than getting wet over night being the problem--but every climate is different and roses respond differently, as we are realizing. A heavy rain followed by dry weather produces no rose disease here--a week of light sprinkles that never quite dries produces disease aplenty.

I don't water every day, even in the heat of summer. That is one of the advantages of mulch. It works for me, fine. It doesn't work for you, that's fine too, but to call it a "myth" is...is that reasonable?

My foliage is wet all the time and I don't really have bs problems, which has made me think that water is not as important as is the susceptibility of the rose to bs.

I guess then I am another one that doesn't really think water on foliage is an issue. Others I know that live in my neck of the woods that grow grafted ht's seem to have many more bs issues. It's just my observation that water on foliage isn't really a factor in b.s. here as foliage is almost always wet. Does rain affect foliage differently than water from a hose? Does the pH of the hose water matter? I don't know.

Mulch has 3 purposes as far as I can see.

1. To decompose and improve underlying soil
2. to provide a barrier - to keep moisture in, weeds out
3. to give a finished look to the beds

If airspace is not left around the plant and if the mulch is too thick water and air can't penetrate bad things happen.

I use mulch around the berries and apples for #2
and use "living mulch" oxalis/violets to keep weeds out of my rose beds.

I think that soil can have too high of an organic matter component but for people in high humidity/high heat or sandy areas that point will never come. In the south in an acid clay I worked hard to keep enough organic matter on the soil as the soil constantly reverted to clay and the organics "burned off." Here, it doesn't get hot enough to "burn off" and just sits.

Johnnidappi what do you use to feed your roses? Is keeping a certain organic level in your soil something you're trying to do, that is letting the microbes in the soil feed the roses?

It's all very interesting, the different views. I know there are a lot of factors that influence all of our opinions and observations in our gardens.

This post was edited by harborrose on Tue, May 28, 13 at 18:55

Well, I recently have been reading advice to clear a space around the trunk of a woody plant, leaving an un-mulched area. Maybe that's to encourage certain soil microbes which feed the plant. But maybe that's also to create a 'well', into which precipitation can drain. Supposedly, it's also to "allow Oxygen in". But DH, a says that Oxygen is rather difficult to keep out. He says that prevention of Carbon Dioxide buildup is (slightly) more likely. (He's the Scientist: I'm the Economist...)

When we were in Oregon, we had access to so much 'Designer Compost' (and gardeners with advanced degrees), that we just top-dressed with compost. Now that we're back in Mississippi (where mulch breaks down rather quickly), we're back to mulching to ridiculous depths. A foot seems about right, to me. But then, I'm a little Napoleon who has the builder's crews here today, turning this home's undersized Dining Room into the Butler's Pantry, and the big ol' redneck "Den" into a dining room big enough for a three-chandelier table. I make my own mulch. It's free. So, of course, I'm going to use a lot of it. But balancing the Water Intake Issue is the Insulation Issue. In a place like Mississippi, where summer heat ranges between 'horrible' and 'deadly', and the December-April cold snaps (invariably following weeks of balmy weather) are no joy either, the plants like having that blanket, for most of the year.

Now that 'Raspberry Crazy Ants' are a possibility, though, I may be rethinking mulch. Frankly, one good episode with the Crazy Ants eating something expensive and electronic (should they show up, this far from the Coast), and I may be calling the realtor, and heading back to Oregon.

Anyone have experience with the 'Crazy Ants' using the mulch as a moist place to live?

In any event, I've always mulched deeply, and have had really good results - particularly considering that I dig small holes for planting (Like I'm gonna pay for more topsoil than I have to?), and am stingy with the water and fertilizer.

About fungus and water on leaves, I think disease comes when you have water and a certain temperature range. I have some blackspot this year on my roses because it has continued to rain up until now, while usually the rain tails off as temperatures rise (I don't know whether day length or amount of sunlight figures in as well). Normally blackspot doesn't show up here until October at the end of the growing season. I rarely had blackspot in my Olympia garden either. This year also 'Alba Maxima' has rust, just the second time I've seen it in my garden. The last time it happened was also during a prolonged rainy spell in late spring.
Certainly too much organic matter in the soil is not a problem here, nor one I'm ever likely to see in my lifetime. I've heard you can overamend vegetable beds with compost. We have extremely compact clay and it eats mulch up. But under the persimmon tree, for example, I don't mulch any more, as its leaves are mulch enough, so there's one place in the garden where I no longer need to bring in amendment.
I agree with Gean's description of the functions of mulch. It also keeps the ground soft and, as Posh says, it provides thermal insulation. When thinking about how much mulch one should lay down, it's worth bearing in mind what kind of mulch one is using. I would put down a thicker layer of wood chips than I would of hay.

I think its always a good practice to till soil (at least shallowly) before laying mulch. But with mulch, as with almost everything else in life, (a) moderation is key, and (b) too much of a good thing is never a good thing.

Before blaming mulch as the culprit responsible for dry conditions, it's important to consider the fact that some soils are, or can become, hydrophobic. When soil actually repels water, the absence of mulch or the presence of mulch (regardless of quantity) is of no relevance.

There's much to be said/learned about how to deal with hydrophobic soils. Anyone interested in the topic should do a simple web search. I'm linking to an old GardenWeb Soils Forum thread that was recently resurrected after a hiatus of several years.

Here is a link that might be useful: Hydrophobic Soil

ilovemyroses,

Your title sums it up nicely. There are many truths in the posts already here. I'm going to chime in on the mythological nature of mulching.

Someone, somewhere, at some time wrote that three inches was a good amount. I have no idea what climate that amount might be suitable for, or any idea what their water bill must be. But that amount is the stuff of myth.

Like others, without mulch, very little would survive for me here. I have never used more than half the mythical depth here, in zone5, or in zone 4. And usually, it is about an inch of whatever mulch material I use. Compost goes down at half an inch or less and never in a solid layer - rather, it gets dispersed.

The decomposition of the compost and mulch that the garden plants (and we for their sake) lustily desire is, at least initially, a mostly aerobic process. Simply put, the material to be composted will compost best if exposed to the air. Also simply, it should be on the surface of the soil. What some do not realize is that it must be in contact with the soil. This is why synthetic weed barrier cloth is bad.

I hope no one will take the 'none' solution of an all-or-none approach.

Mulch is good - very good in fact.

Here is a link that might be useful: Wiki on Compost

windeaux, when we went through our drought a few years ago, there were times it would rain and it would not penetrate the mulch. I did read that mulch can act as a shield and prevent water from getting to the soil. Especially if the mulch is thick and dry. I then started clearing my mulch from around my rose bushes if it was going to rain.

Also, the type of mulch is important. I have been buying mulch that is manufactured to direct the rain water too the soil and not be soaked up by the mulch. I find that it has made a difference.

Thread link:

Here is a link that might be useful: Mulch

generally mulch is applied after the winter rains, in order to maintain deep moisture in the ground. I do mulch around my veggies,just once when I have made sure the soil is already damp. I don't do a very thick layer since I don't expect it to prevent weeds (it doesn't) and it is usually quite friable compost so it has pretty much disappeared into the soil be the time the ground is really beginning to dry out....and then I water or harvest. With ornamentals, I use all the space for growing plants because I am less interested in getting a 'bumper crop' of giant blooms (whereas I am very keen to get a great crop of potatoes).

But mulch - horses for courses, really.