This is a gardeners question and is more biology that thechnology. After clear cutting the trees in site preparation for new developement, the stumps are often ground for landscape mulch. Several gardeners have complained that this “root mulch” has burned their plants. Are extractives of some species concentrated in the stump and roots so that mulch ground from them are toxic to plants? I recall that many, many issues ago a FWW report on vacuum kilns reported that the condensate from the vacuum drying process was toxic to plants.
BJ
Gardening, cooking and woodworking in Southern Maryland
Replies
The micro-organisms that attack the wood chip uses the nitrogen from the soil and ties the nitrogen up, ie growing plants have a low amount of nitrogen. I'm guessing the "burning" is a sign of nitrogen deficiency. Cure: add some 36-0-0 to the wood mulch occasionally.
I usually see 'burning' in the context of too much nitrogen, as in too fresh chicken manure.
Edited 5/5/2004 1:39 am ET by Uncle Dunc
As in most things, too much causes a problem. I would not suggest pouring the whole 50# bag of 36-0-0 on a plant. If anything I would error on the light side.
BJ, I think Dale's nitrogen depletion explanation is valid with respect to what it does to germinating plants...But as for your other question about the toxicity of wood extratives, some species produce natural herbicides that help to repress competing vegetation that tries to get establish within the trees drip line. For example, the juglone in walnut is a very potent herbicide. It is especially effective against members of the pine family (Pinus) and also species in the Solanaceae family, which includes tomatoes, potatoes and peppers.
Some woods have very powerful chemical herbicides. Black walnut, for instance, has "Jugalone". Eucalyptus has the characteristic fragrant oils. Most plants have active chemicals in them and lots of those chemicals are herbicidal.
I got adult onset asthma a few years ago and got religion about air pollution. We chip all of our orchard and landscape prunings with a PTO chipper and use some for mud control, but compost most. We leave them for a year or two until they are good black compost and all herbicidal activity is gone, metablolized by bacteria and fungi. Compost all organic matter and you won't have toxicity problems and you'll have a great gardening material.
PS: If its too big to chip, use it in the fireplace, or turn it into bowls, or slice it into boards.
Bee Jay, I like your question, and while I am not a scientist, i would like to take a stab at it. I have been a furniture maker for over 30 years, and don't believe in TV, that is I don't live with one' so I read a lot, and have always been a close observer of nature, so here goes.
Yes there are trees that have extractives in them that no self-respecting vermin can eat even in hundreds of years under certian conditions. I live in Arkansas. Our rot conditions are about as good as anywhere in America except Florida, and Lousiana. When I walk around in the woods, I often see old relics of trees, and the last reminants are usually the crotches , stumps and burls, or knots.
I brought home one such piece about 20 years ago that turned out to be the oldest tree in Ar. at the time. I took a cross-section to Dr. David Stahley at The Uof A. He had a young fellow named George Emory, who did his masters thesis on my find. I have both of their studies of this area, and have spent many wonderful hours reading contemplating and observing.
As it turns out, and I am also a woodturner, and have a sawmill, so I bring home lots of trees. Most of the stuff that I'm looking have these very properties. That is the better the color, the more extractives,and more figure is what I am after. sometimes I leave things to rippen/spalt, sometimes I cut it fresh, but one thing I have noticed is that I have one of the healtist worm-farms in the world.
Worms love to live under stumps and in wood shavings or chainsaw chips. they seem to promote a fungus or have a symbiotic relationship that breaks down just about anything.
These guys are in about 2" of mulch on top of asphalt, and they are so strong and vigerous that they can jump out of a 2# coffee can, and when I go fishin, the fish had better watch out.
So my advice to your friend is to go to the nearest baitshop, and buy a bunch of worms, and maybe to the garden store to guy some cow-manure if you are out West or someplace that is fungi-starved, and add water. Rot can only occur at about 30 to 50% moisture content, I think. And don't poision the beetles either,they are part of the soup, and they are not after the house yet unless you have a moisture problem.
If you are in a zoned area the code will have required termite protection in the footings. so feed the decay, and it will turn this stuff into soil in no time.
so take an alergy pill, and good luck, Keith
Bee Jay- If the chips or grindings are stored for too long in too large a pile, there is a chance for anaerobic bacteria to build up to the point of releasing toxic gasses that can cause the burning. Let the mulch air out a bit and that might help.
Stash
Depends on the tree species and the soil type Ph (acidity / alkalinity) it's grown in.
Some softwoods with lots of resin content can make mulch a little toxic to some susceptible plants.
More often than not - the mulch will "sour" the ground - if the parent tree was grown in acidic soils (least thats broadly the case downunder).
What happens is the moisture taken up by the tree is slightly acidic, hence the sap is slightly acidic. Then of course that means the mulch is slightly acidic and it can 'sour' the ground if it was already acidic to start with.
Usually here at least - most folks who add mulches from tree bark, sawdust etc add a good helping of crushed dolomitic lime to 'sweeten' the soil - in turn cancelling out the acidifying effect of the mulch.
In addition to those aspects - theres also the tree bark to consider.
Some forest species that shed their bark annually (like our Eucalypt species) don't like competition for light moisture and space from dissimilar or even their own kind...
The Barks that shed and pile up around the base of the tree sometimes many feet deep over a few years, if no fires burn the underbrush (ours os a very fire adapted forest species of trees environment) contain large amounts of natural tannins. These will leach out and make there way into waterways turning the water tea colored brown....
These tannins can be a natural form of herbicide the trees produce to deter other species from germinating around their base and thus competing for light space and moisture / nutrients.
So - Bark mulches, if from the wrong species - can in fact kill some susceptible species of plants.
Hope this is of some help and your right about the condensate from evaporateive dehumidifying kilns...especuially when drying our Eucalypt hardwood species, killing plants-I use it to keep weeds down around the factory perimiter etc..while the kilns running.
My first post here so by way of intro - I'm a former forester / wildlife officer for our states Conservation Authority, who owns a timber milling, drying and furnituure manufacturing facility in the south west of Western Australia amongst the magnificent hardwood eucalypt forests. Lovely place - tough to make aliving but!
Enjoy fishing, am a pro fishing trout and saltwater fly fishing charter guide (when not butchering wood)
Live on a small 28 acre deer farm, (which the bank & I jointly own), alongside the states longest river which holds stocks of rainbow trout and a large endemic freshwater lobster. married 3 kids all teenagers (god help me).
Always broke...but I am told I'm lucky and live the "life of Riley" - just twixt us - I'd gladly swap with Riley if it meant I could give up timberwork for full time fishing and a big boat!
Cheers!
Lotsa arborists and others around here make topsoil from wood/leaf chips by having cattle graze over them then composting and mixing with loamy sand.
The wood has to rot to beneficial to soil structure and critters....until then the rotting process consumes soil minerals and critters as was already said...especially nitrogen.
Add a balanced fertilizer and lime, and the relatively small amount of chips won't be a problem.
“When we build, let us think that we build forever. Let it not be for present delight nor for present use alone. Let it be such work as our descendants will thank us for; and let us think...that a time is to come when those (heirlooms) will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, ‘See! This our father did for us.’ “ --John Ruskin.
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