My advice would be to ignore your landscape architect. If you use leaf mold or triple shredded hardwood, the mulch will break down and add nutrients/organic matter to your soil. I did a mulching experiment in my garden last year and added to it earlier this year. I have three conditions:

1. pine bark (chipped trees)
2. leaf mold and newspaper
3. ground bark.

The leaf mold beds stay moist longer and don't have any more weeds than the others. The plants in the pine bark bed (daylillies and blackeyed susans) aren't spreading and look more stunted (lack of water?). The ground bark bed (I used leaf mold last year) is drying out faster than the leaf mold bed (but it does "look" neater).

Now I don't water so my practices contribute to the problem, but the point is that for my garden, leaf mold/newspaper provide must better moisture retention and the soil in those beds is quite silt-like. In the pine bark beds, the clay soil hasn't been enriched beyond when I first built the bed. Too soon to know what the ground bark will do in terms of soil amendment.

Thanks for the response.

Now, here's my dumb question: what exactly is leaf mold and where can I get it? (I live in Apex)

I should also add that I'm planting in new beds that are about 8"-10" deep on top of 8-10 pages of newspaper on tall fescue that I scalped before laying the newspaper. The bedding material is a blend of 1/3 screened topsoil, 1/3 compost, 1/3 aged manure. With that in mind, is your recommendation still that same?

Thanks again!

Leaf mold is partially decomposed leaf matter, used as a soil amendment. I get mine from our town Public Works department for free.

Over time, whatever you plant is going to absorb the nutrients you're building into the soil right now. The leaf mold will serve as a renewable source of soil nutrients as your plants grow. You could provide all their nutrients through chemical fertilizer but that would cost more and not provide the organic matter that make worms so happy. Also remember that rain, wind and time are constantly leaching out nutrients, so slow release nutritional sources are bound to keep your plants healthier.

Here is a link that might be useful: Garden Helper Dictionary

I like the larger chips of the pine bark mulch, as they last much longer than the more ground up types.

The "soil conditioner" sold in big 2-cubic-foot bags in garden centers that are lighter than the bags of topsoil or compost half their size (the big brand USED TO BE called "Nature's Helper," but I don't see that brand any more)... anyway, they're ALL finely ground pine bark, which is also a constituent of most potting soils. What's great about this material is that it will make clay hold LESS water and make sand hold MORE water, so it improves your soil whether it holds too little or too much water.

If you buy the regular "pine bark mulch," it will degrade into the equivalent of this over several years, and be incorporated into your soil via rain and earthworms. Hardwood mulch actually DOESN'T make as good of a mulch as far as providing nutrients to the soil along the way goes.

As for how well ground your mulch is, if you're buying the bagged mulch, it's usually at least double ground, unless you buy the actual pine bark chips, like jbcarr is talking about, which I don't care for, as they're actually large chips of pine bark and not comfortable to walk on -- and take A LONG TIME to degrade. When you buy pine bark mulch by the scoop, you usually have a choice of single-ground or double ground, and I usually save the money unless I really need it to do quick second duty as an amendment and just get the single-ground, as it lasts longer, and eventually breaks down, anyway.

Then, of course, there are the colored mulches, which I've never gotten, but I guess you could, if you have a reason for them. I'm not sure what the proper use is for hardwood mulch, as ever since I learned pine bark mulch is much preferred for plant nutrient purposes, I've not used any of the hardwood mulch... I imagine there are circumstances where it's the best choice, though.

Leaf mold is really better if you want a mulch that's really more something you want to actually amend your bed. A lot of folks actually use nothing but pure leaf mold to pot plants in, which is all we generally use at Hatcher Garden when we're potting up plants for the sale...

No matter WHAT you use, probably the most important thing to remember is to NOT put it right up to the trunks of your shrubs/trees or the crowns of your plants, as that encourages potential rot, fungi, and easy, difficult-do-detect access by critters like termites and voles.

Happy Mulching!
Jeff

There seem to be quite a few differences of opinion as to whether bark or hardwood mulches are better. But the best overall advice I've found on mulching is this suggestion for forest floor mulch. What I'm curious about is why bark is not a good mulch. It's organic and natural and seems that it would be good. Terri, can you explain this? I think I agree with you; I just want to understand more.

Shelley

Here is a link that might be useful: Mulching

I can't find the notes I took at a soil workshop I recently attended, but the goals in amending soil are to ensure: 1) good soil aeration or oxygen, 2)proper drainage or movement of water through the soil, 3) proper water retention based on the soil type and 4) prevention of soil compaction. Bark mulches are large discrete chunks; leaf mold easily compresses into layers but still allows air circulation. Furthermore, leaf mold breaks down slowly, releasing nitrogen and other needed nutrients into the soil. According to Cornell, (see link) if you mulch with bark, you need to amend the soil with nitrogen in addition to the mulch.

Here's another fact I found: The ability of leaf mold to retain moisture is almost miraculous. Subsoil can hold a mere 20 percent of its weight; good, rich topsoil will hold 60 percent, but leaf mold can retain 300 to 500 percent of its weight in water. Composting Guide

Enough?

Here is a link that might be useful: Cornell Factsheet on Mulches

I have been reading quite abit on this subject, and the biggest deterrant to using hardwood chips as mulch for soil amements is the FACT that hardwood actually REMOVES nitrogen from the soil as it decomposes. so massive nitrogen like urea or heavy compost tea in necessary if you want to use wood chips for amendments. If, however you want the mulch to keep out weeds and other plants nearby, woodchips are for you,as it will starve the plants nearby of nitrogen. but again, you will need nitrogen added to get plants to grow properly in it.
this is not my personal experiance, as I am quite new to this, but this is what I have read in organic gardening books and such.
I have been using leaf muld, and I am looking into vermicompost, with the wormcasts, it looks like the ultimate compost for soil fertilization. and I can stick to the leaves for the amendments. I have several hundred oaks, maples, poplars, walnuts, and so on for leaves on my little farm, I need a bit more greens to compost properly, but I am getting there.

OK, I read all 3 of the interesting and informative links Shelly and Terri included (thanks... never too much info), but I'm still where I started on this subject, and I beg to differ with the statement on the composting page about the water holding capacity of leaf mold...

As I've said, that's ALL we use at Hatcher Garden to "pot up" perennials and annuals into 1-gallon containers for our bi-annual sales (because it's FREE, from the city!), and straight from our horticulturist's mouth (who oversees every one of these thousands of plants)... "this stuff is easy to work with, but it sure doesn't hold water." Having bought a good number of these plants through the last few sales (probably more than 50), I can attest, firsthand, that they generally require watering EVERY SINGLE DAY unless it's cool and cloudy. And these are planted in 100% leaf mold.

Another thing about leaf mold and leaf composting, in general, which was sort of glossed over or not mentioned at all in the links, was the fact that most leaves are NITROGEN HOGS when they're decomposing (just like sticks and wood chips). So your big pile of oak leaves that you have sitting up, waiting to use as a mulch or to incorporate into your soil, or pot your plants in, UNTIL it's well decomposed will be USING nitrogen (or rather, the bacteria doing the decomposing will be using the nitrogen, which they then release when they're done, and pass on to the great bacteria farm in the soil), so be careful with that.

I didn't know all this when I started a raised bed around a tree partly with freshly ground small oak limbs and leaves... and even though I discovered this fact part-way through my first season and added nitrogen, I had NO LUCK with anything I planted that first year... the bed is fine and dandy now, after three years, though.

I still contend that ground pine bark mulch that's NOT matted and NOT applied in a matted fashion (applied loosely, as should all mulch be), is a good choice in many situations... and if you can afford it, the shredded bark (soil conditioner) is an even better choice, although I wouldn't apply as thick of a layer of that.

By the way, there's a 30 x 25-foot area of my front yard that was too shady for most grass, so I killed what little grass grew there in 2002 and decided to try growing wintergreen (Gaultheria procumbens). I'm really a little south of its maximum heat zone, but I put a soaker hose all through there (it likes moist, woodland conditions), and the first couple of years I shredded all the leaves in the front yard and spread them over that area (Note I also heavily fertilize that area with acid fertilizer several times each spring -- wintergreen likes a pH of 5.25, AND add some aluminum sulfate to bring down the pH, as my starting pH ended up being 6.7, which surprised me). It's slowly spreading and filling the area, with my main concern being having to pull out other things that are more aggressive and also like to grow in that woodland environment (including poison ivy -- ACK!). The last couple of years, due to health and time issues, I've just blown all the leaves into that area and not bothered to shred them, and it still seems to do OK... The leaves actually COVER the wintergreen for much of the winter and early spring, and then as they start to break down and settle, the plants with the most previous cover seem to be the most vigorous.

Like anything else in gardening, there's plenty of different ways to do it, and I suggest anyone who has the time, the space and the materials to try the different options you find interesting and see what works best for you... Since I'll continue to have LOADS of oak leaves every year, I'll find SOME use for them, but I'll also still be buying bark mulch and soil conditioner, because trees and shrubs WITH it just seem to do better...

As for the comments on the mulching link about Mychorzzia (sp?), I've read about that a number of other places, too... that's even how truffles work, as they're a fungus, and it's the tree roots that give them the sugars that make them such a delicacy (recent article in The American Gardener, I think)... Funny thing, though... the fastest-growing tree I have now (by a good measure), is my Peggy Clarke flowering apricot (Prunus mume), and it's the second one in that spot. The first died the spring I planted it, which was very wet, and I suspected some sort of fungal rot, so prior to amending the soil some more so I could both improve it AND bring it up somewhat ABOVE grade to make sure the new one didn't have roots sitting in water, I gave the previous hole a Daconil DRENCH... I mean I SOAKED it with several GALLONS of fungicide, and let it sit for a week or so (not thinking about Mychorzzia AT ALL at the time). Of course I've really fertilized and carefully watered that tree when we didn't get enough rain, too, so I'm giving it all I can, and it's at least doubled in size since the growing season started.

So who knows?
Jeff

One more thing about nitrogen. Soil tests do not give nitrogen levels--they simply recommend adding 1 pound per 1000 sq feet on the assumption that your plants will only use what they need. The PROBLEM with this recommendation is that it doesn't consider the damage nitrogen does when it leaches out of the soil and into groundwater or water bodies. Excess nitrogen is the most significant source of algae blooms in our lakes and reservoirs. Algae blooms cost your local water utility additional work and money--thus raising your utility bills.

So IMHO managing your gardens nitrogen levels with leaf mold is a very positive environmental step toward preserving water quality and it doesn't hurt or damage your garden/plants in any way.

Terri's got a lot of good points here, except the fact that the decomposition of ANY organic material into humus (see link) is done by loads and loads of tiny micro-organisms which use nitrogen as a means to 'eat' the plant matter being decomposed. When you add any of these mulching materials your soil WILL go through a 'Nitrogen Depression' which simply means, until your organic matter becomes humus, the micro-organisms will pull the nitrogen more strongly than plant roots will. The faster an organic matter decomposes, the more sever and sudden the nitrogen depression will be.

Taking all this into account, lets assume that we mulch our beds with leaf mold every year. In that case, a few weeks after you apply your leaf mold, you will deplete all of the nitrogen that last year's leaf mold has captured, and you will more than likely see a sudden drop in both plant growth and the decomposition rate of your leaf mold!

The use of pine bark mulches will do much of the same. Depending on weather you use pine bark nuggets or finely shredded will have an impact on how fast it decomposes. As most all pine products decompose, they release ascorbic acid which will lower the Ph of your soil; this is true of both pine bark mulches and pine straw mulches. This creates an ideal condition for Rhododendron, Gardenia, Mountain Laurel, Nandina, Viburnum, and Blueberries.

The use of hardwood mulches will make your nitrogen depression much more subtle because of the moderately slow rate of decomposition.

All in all, the end result of mulching is to 1) help hold soil moisture 2) create humus. The creation of humus from organic matter WILL use nitrogen, just a matter of how much and how fast will determine your specific need. The use of a slow release synthetic fertilizer or FULLY DECOMPOSED manure (manure from poultry houses really is the best) will significantly increase the rate of decomposition of your organic matter, therefore making the nitrogen depression far less noticeable and harmful.

Kevin T. Barbee
NCSU Soil Science Graduate Student

Any idea how long it would take for leaf mold to break down enough so it doesn't cause nitrogen depression? We have 7 acres of oaks in SC, so of course we have a limitless supply of leaves. Can I pile them in a compost bin for future use, or is there more involved than that? Or is it better to use them directly on the garden and supplement the nitrogen?

you can pile them, but you'd be better off shredding them first (via a lawnmover or some kind of chipper/shredder). different types of leaves take different amounts of time to break down...and oak leaves take much longer than others. some people bag the leaves and throw them somewhere out of site for a few seasons, but layering them in compost (alternating with greens), would work well (you don't get leaf mold in that case though, you get compost).

decomposed leaves are great, particularly if they are your own. though i use city compost, you never know for sure what people have thrown in with their green waste which the city collects and composts.

Yikes -- I've read this thread twice and I still have questions. This is my first year gardening and even after weeks of research this thread has raised some critical issues I wasn't aware of. I was planning on using cardboard/newspaper and then leaf mold followed with a pine bark mulch. So if I use leaf mold, how do I know how much nitrogen to add to my soil? It seems that the more decomposed the mulch, the less nitrogen I will have to add, but how does everyone know exactly how much nitrogen to add.

It is my understanding that once the organic matter of whatever sort is mostly broken down, it starts to "give back" the nitrogen so it's really the freshest OM that is a major problem. If you are mixing the fresher OM with soil, then the using-up of nitrogen is a generally "universal" phenomenon, so adding a bit of slow-release nitrogen fertilizer, or cottonseed meal, alfalfa meal, etc., would prevent any problem. If you are using half-rotted/composted material and NOT mixing any "new OM" with it, there should be sufficient niotrogen for your plants. Adding extra, in the form of an organic, slow-release fertilizer or as cottonseed meal or alfalfa meal, is a guarantee that you won't run short, nor will your plants. If you are using a partly aged OM as a mulch, then the only place you should see any nitrogern deprivation is at the surface of the dirt, at the interface, as it were, of the dirt and the mulch. A scattering of fertilizer or meal on the dirt, before the mulch, would take care of it.

In short, most people don't know. It's not really practical to take a soil sample, send it off and wait for the results before adding fertilizer. Not knowing, and fearing to add too much at any one time, is one reason some organic gardeners don't use fertilizer. Using a slow-realease fertilizer, or a grain meal (which is also slow-release) is one way to try to apply only as much as you think your plants need and will need. As with salt in the soup, adding is easy, it's the taking out that is HARD!!

Livvy, if you still have questions about mulch and compost, go to the Soils, Compost and Mulch Forum and read the FAQ. Probably, most of your questions will be answered.

If you're looking to condition your soil, I suggest hardwood mulch. It will break down and create a rich, black topsoil in less than 2 years. If you get green mulch, toss some lawn fertilizer over it so that the mulch doesn't deplete what's there already.

If you want top dressing, weed control and thermal insulation go with LL pine straw.

I have heard MG's on the radio whose advice I quickly disregard. It's like a pediatrician who doesn't raise his own children.

Thanks so much. My head is just swimming with information on pests, companion plants, ph values, and other info that as a wannabe gardner I just crammed in there for the first time in the last couple months. This is very helpful. I'm heading over to soil forum now.

One caveat. I have read in several sources that I trust - although they may all be citing the same study - that vegetables and flowers do better with hardwood - or straw, bark, etc. - mulches than they do with a pine straw mulch. Trees and shrubs do very well with a pine straw mulch.

We've always used pine bark mulch (the more coarsely ground stuff). Its easy to move around and it keeps most of the grassy weeds out. All I really pull out of there are tree saplings (some of them I plant in different spots in the yard). Last year I found a dogwood seedling in there. Its good if you don't want your perennials to spread a lot and take over the whole bed as well.