I've never heard of leaves that harm compost. When fully composted (or
completely broken down into leafmold apart from a compost) all leaves
become the same healthy enrichment. But undecayed or half-decayed, the
juglone in walnut leaves can retard the growth of many plants, so it would
not be wise to use fresh-fallen walnut leaves as an uncomposted mulch in
gardens. But they'll be fine once they're coposted, the juglone completely
-paghat the ratgirl
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I also thought intuitively that putting white-fly infested leaves from
my poor Hibiscus was a no-no, but gardener disagreed.
Might this have something to do with heat of composting? Or?
Is there any science to settle this once for all?
Those who cannot remember the past
are condemned to relive it.
I assume you're talking about leaves that have naturally fallen from trees.
Leaves with waxy coatings such as Southern Magnolia and hollies are slow to
compost. However, I run my magnolias through a shredder and they do fine.
I don't compost holly leaves because of the prickers.
John Henry Wheeler
USDA Zone 7
You may want to avoid composting:
Rhubarb leaves (oxalic acid)
Oak (leaves are rich in nitrogen but slow to decompose.)
Spruce and Pine needles (high in acid and resin, slow to decompose)
Each of these has special problems. Some tend to kill the bacteria that
do the composting. A skilled, patient composter will have no problem.
Black Walnut shells (juglone - herbicidal toxins)*
Black Walnut leaves (juglone - herbicidal toxins)*
Weeds with mature seeds*
Diseased or insect infested plants*
Poison Oak and Poison Ivy*
*These materials should not be used in gardens unless they are
completely composted. Once composted, none of these materials pose any
Shinny leaves like laurel, holly, and rhododendron are slower to
decompose and compost better if chopped first.
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I've never seen oak leaves that were waxy. Mine compost very quickly. In
fact, they've turned to leaf mold sometimes when I've left them in a bag for
a few months. I love oak leaves in the compost. My problem, sometimes with
maple leaves is that they stick together.
John Henry Wheeler
USDA Zone 7
It probably depends on the type of oak. My live oak has leaves that are
small, hard and glossy and they take time to break down. My Chiquapin and
Monterrey oaks have large glossy leaves that are more flexible and they
break down quite easily.
Same family, different characteristics...
As far as I can tell from the list of posts, the original question was
why would high in nitrogen oak leaves decompose slowly.
Tree leaves of any kind, assuming they're the leaves that have fallen in
autumn, aren't high in nitrogen. The opposite, actually, they NEED
nitrogen (green matter) to decompose quickly. Fallen leaves are high in
carbon, not nitrogen.
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