composting leaves -- any to avoid?

[Dennis Edward]

For the most part, people say you can use leaves in compost. But I've heard there are some tree droppings you should avoid putting in compost. Anyone know which ones?

[paghat]

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 breaks down.

-paghat the ratgirl

[Vox Humana]

I always read that it isn't a good idea to put diseased leaves into your compost pile. That doesn't have anything to do with a specific type of tree, but it is probably a good policy.

[Persephone]

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?

Persephone

[Snooze]

It seems many rosearians recommend not using rose cuttings in composts, because fungus spores can supposedly survive and be spread about the garden.

Walnut leaves they can inhibit growth.

-S

[Compostman]

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 Washington, DC USDA Zone 7

[Stephen Henning]

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* Crabgrass* Ivy* 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 problems.

Shinny leaves like laurel, holly, and rhododendron are slower to decompose and compost better if chopped first.

[Ann]

Stephen Henning expounded:

True, but chopped up, they make wonderful mulch for a perennial border, far nicer than bark mulch!

[Compostman]

Why would a high in nitrogen oak leaf decompose slowly?

[Ann]

"Compostman" expounded:

Because they almost seem a bit waxy, I guess. Maple leaves turn to dust much quicker than oak leaves do, in my experience.

[Compostman]

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 Washington, DC USDA Zone 7

[skwehe]

[RobinM]

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.

Robin Alexandria, VA

skwehe wrote:

[Gary Groundhog]

"Dennis Edward" wrote in news:m6Gif.637964$1i.395818@pd7tw2no:

If you live near a forest, don't compost anything that a bear has used for toilet paper.

[George.com]

avoid too many pine needles, 10-15% of your compost mass is the maximum I have seen recommended.

rob