Mulch: Oak vs. free(mostly pine) vs. cheaper(pine+deciduos)

Colorado Springs, CO(Zone 5b)

Which is better, oak mulch or pine mulch? I'm doing mostly xeric plants or low water plants in a hot no shade area, and have automatic sprinklers that I'll soon turn into drip sprinklers. TrishaG just told me oak is allelopathic (releases chemical to other plants to kill them, for competitive purposes). Plus she confirms her xeric plants don't like a lot of moisture.
Nate & Jack's Forestry Service sells 100% oak mulch saying it holds a lot of moisture and that pine mulch can destroy your soil over time. I know we used pine mulch for our blueberry farm but they required acidic soil.
Colorado Springs area has free mulch at Black Forest Slash & Mulch http://www.bfslash.org/. It is probably mostly pine since Black Forest is blanketed with pine. (unlike Denver that I've heard separates pine mulch from deciduous mulch). Thanks, Arlene

Los Alamos, NM(Zone 5a)

Wish I could answer your question. I use a lot of pine needles as mulch. It works fine for me and decomposes quickly when used as mulch -- not anywhere near as fast when I compost it. I have heard that pine has allelopathic reactions, too, and I have heard all the horror stories about what pine can do with soil. My local county extension agent thinks pine needles are great for our soil which tends to need organic matter and is neutral at best. Oak leaves were great mulch when I lived in the South. Don't know if that is the case in the west, but I can't see why oak leaves would be different here -- okay, they are different species, but they are oak.
You didn't mention whether you were talking about oak leaves and pine needles or ground up oak or pine wood! Wood is a different story. It sucks nitrogen out of the soil when it decays. If it is wood, you will need to add nitrogen to support the decay of the wood as well as the needs of the mulched plants.
I compost pine needles. It takes forever, but I have never seen any problems in the plants I grow. It does promote an acid condition, but most western soils are neutral to alkaline and some extra acid just makes nutrients more available to plants.
If you can get these materials, I say go for them. But I am no expert. I just know what I have done in my own gardens over the years.

Colorado Springs, CO(Zone 5b)

Thanks Paj. The oak mulch is wood (not leaves) and as far as the free mulch, it mostly pine wood, but since it is free at the city composter, I'm sure some needles get mixed it the grinder, along with a few deciduous trees. Thanks, I'm leaning toward the free mulch (mostly pine).

Albuquerque, NM(Zone 7b)

I thought allelopathic inhibition was caused by living plants, not dead and chopped up ones. Could be wrong.

Los Alamos, NM(Zone 5a)

Don't know when the allelopathic reaction occurs, but pine needles are great mulch and are baled and sold for money in the South where their plants mostly require mulch of the acid type.
Wood can sap out all your nitrogen as it decays, so be sure to add extra. I killed a crop of potatoes once by putting a truckload of wood chips on them for hilling.

Colorado Springs, CO(Zone 5b)

Paj: thanks for reassuring me pine needle mulch is good . I just picked up my free pine mulch and it is only 15% wood and a lot of pine needles, kind of surprising, but I think each batch is different. That is in the truck bed waiting until I rototill in some 1 year aged horse manure into the sand/clay for my xeric section. I'm trusting those people who say 4-6 month aged horse manure will produce 150 degrees to kill the seeds!!! dparson: good to know allelopathic mostly applies to living plants. Thanks both!

Denver, CO(Zone 5b)

I think the pine mulch will be fine. If you have strongly xeric plants, don't water too much, especially once they're established. I use whatever shredded wood mulch on my beds and it works fine. I usually need to rake it up after a couple of years and replace it, but it does help keep the soil cooler and holds in the moisture. I don't water much, so anything to insulate the roots is good for me.

Aurora, CO(Zone 5b)

Our soil is so alkaline, that the myth of pine based mulch causing it to go acidic just doesn't apply here. It would take far longer than we have life left in us. As far as it breaking down, I have left piles on my driveway (not much unlike a pic that Kenton posted before) and it mulches quite nicely all by itself. As a matter of fact, I found the largest worm yet seen on my property and the pile is a foot from the edge of the drive. On the horse poo, you should be just fine.

Los Alamos, NM(Zone 5a)

Yep, the horse poo will supply the nitrogen needed to break down the wood. The pine needles are great for alkaline soil. I don't know how they got such a bed rep out west. In the South -- where most if the soil is already very acidic, they use pine needles to mulch acid loving plants.
On soil characteristics ( acid vs alkaline) my county agent says, no matter what you do, the soil always wins. I thought that was very wise.

Albuquerque, NM(Zone 7b)

Calcium carbonate has a good buffering capacity.

Los Alamos, NM(Zone 5a)

Where do you get calcium carbonate? It probably adds calcium to the soil as well.

Albuquerque, NM(Zone 7b)

It is in my soil in great quantities and very likely in yours as well. It is what keeps the pH alkaline in the long run in spite of the additions of acidifying additions. Calcium carbonate is the active ingredient in agricultural lime. The corresponding acidifying addition is Calcium Sulfate, commonly referred to as Gypsum.

Los Alamos, NM(Zone 5a)

Gee, thanks. I don't think I need to balance my soil. It is pretty close to neutral according to a home test I did. It might be that a real University soil test would find otherwise, though.

Albuquerque, NM(Zone 7b)

Neutral is nice.

Los Alamos, NM(Zone 5a)

Sure is. It may be slightly alkaline in places because I still have to keep adding organic matter to keep the leaves from yellowing.

Colorado Springs, CO(Zone 5b)

New question: My friend Herb just bought a 6" chipper yesterday. I was going to put the chip mulch on my front yard. My grandma in Michigan just told me chips have to be "aged" - she wasn't sure how long. She is basing her mulch advice on her own sawdust experience from years ago that killed a plant of hers (she's not sure what type of plant it was that died from the sawdust). She couldn't recall if the sawdust came from lumber or a tree, or what type of tree/lumber it was. My friend will give me pine chip mulch, and will be whatever I choose so I will probably ask for mostly pine wood chip mulch instead of pine needle mulch. Do I have to age mulch or not - no one mentioned it before in this thread.

Also, any advice on the best size chip for the mulch to be (since we might be able to change settings on the chipper)? Thanks!

Los Alamos, NM(Zone 5a)

Your grandma is right. Sawdust or wood chips will deprive the plant you put it on of nitrogen which will kill it. Aging it means getting the rotting process started so it will feed the plant rotten wood rather than steal the nitrogen from the plant.
You are much better off with pine needle mulch. It isn't wood and will help make your soil more acid. It is better to age pine needles as well, but if they are ground fine enough they might be okay at first. One way or the other get your wood chips as small as you can get them and preferably get ground up green stuff --like tree leaves.

Colorado Springs, CO(Zone 5b)

I'm aware of aging but any idea for how long to age chips? Thanks!

Los Alamos, NM(Zone 5a)

Unfortunately, a long time. I have two stacks of woodchips in my back yard. Mix some nitrogen in with them and they will decompose faster -- possibly grass clippings, manure, or alfalfa chips. When they start looking dark and rotten they are ready. Mine have been there about 5 years.
We can get free wood chips from our county which has a shredder as big as a house. We use them for paths and places where we don't want grass and weeds to grow. The county mixes them with manure and sewerage sludge and composts them about 4 months. In the winter we can see the piles steaming. The finished product still contains lots of wood chips. We remove the larger ones before using on our plants.

Aurora, CO(Zone 5b)

paja, I've used fresh chips that our city puts out from trimming all their trees and never had a problem. Do you think that with the sawdust that it was put on a bit thick and didn't allow enough water to penetrate to the plant? When i first moved in here and started removing rock in favor of mulch, it all came from the city. Sometimes there would be leaves mixed in pretty good, other times no so much. This spring, they added all the christmas trees with the cities, and it is quite nice, especially when moving it around. Christmas in March. : ) Also, I have left some sitting on the driveway before I could get to it, and it would start composting like you mentioned. I'd clear off some of the older mulch and put this underneath, putting the old on top. Man, did I find some worms in there.

Los Alamos, NM(Zone 5a)

Well, what can I say vadap. Perhaps your wood chips are ground smaller than ours? I don't know. I did destroy an entire plot of potatoes once by mulching it with ground up wood from our county dump. I have some wood chips of my own that are in a pile rotting and, yes that pile is full of worms, but this is 5 years later and they are ground fine. My pile came from tree thinning in my vacant lot and is ground pretty fine.
Maybe our joint advice to arlene should be be careful with the wood chips. I do know they make good paths because they kill the grass and weeds underneath, but you usually end up having to remove them annually.

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