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I live in southern Arizona and we have four varieties of Oaks here that lose their leaves in the springtime as opposed to the fall. I know one species is called Emory and another the Arizona White. What the other two are I am not sure.

Are these leaves good for mulch?

My neighbor says they have too much acid. He has a huge pile of them and nothing grows on top of them. The pile is about 20 x 20 feet and 6" deep. It has been there for about 3 years undisturbed and there is very little mulch underneath.

Why?

  • Open/flat pile, dry area, slow breakdown, as the "pile" is too dry. Enclose and get them damp and things will progress. – Ecnerwal Apr 15 '17 at 13:47
  • The acid is the tannin. Many oak leaves are hard to decompose, but 3 years is way too much. I think there are other reasons. It would be good to know how was the place before they put the leaves. I would assume the soil was already degraded. – Giacomo Catenazzi Apr 16 '17 at 15:49
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Assuming that all four trees you mention really are Quercus varieties, oak leaves make the best leafmould - they break down faster and make quality leaf mould. The way to produce leafmould is to put the leaves in black plastic sacks, poke a couple of holes in the bottom, if the leaves are already wet, fine, if not, add some water, tie the tops shut and stack them somewhere out of the way. After 1-2 years, the leaves should have reduced right down to what looks like crumbly black or dark brown material in the bottom of the bags, and that can then be used as mulch, or dug into soil.

I've no idea why your neighbour's pile of leaves hasn't bio degraded at all, not even on the bottom, it doesn't really make sense unless you live somewhere pretty cold, but bagging them up in the way described above works really well, and is definitely quicker and more efficient than just leaving them in a pile somewhere. More information see this article on Leafmould.

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  • You got the right idea with the temperature I think, but in the opposite direction. The heat and lack of humidity causes rapid evaporation. I had a compost pile in Arizona I had to water in order to keep the decomposition going. – Fondor1 Apr 17 '17 at 18:34

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