Most fungus in mulch is at least harmless, and much of it is actively beneficial. If you are seeing a network of fine white lines, that is a good kind. Why not take a picture for us to look at?

Possibly what you are seeing is not a fungus but instead a slime mold. Lovely name, isn't it? They appear on mulches from time to time. I had some a couple of years ago. It did no harm, and in my garden, did not reappear.

Rosefolly

Here is a link that might be useful: Slime mold on mulch

Oh, Rosefolly, thank you for that link. A few years ago I put a big Talavera turtle planter on top of the stump of a tree, and eventually found that slime mold (whose name I did not know until now) had basically cemented the planter and the tree stump together. It was quite bizarre, and now I know what it was.

Susan

I agree with Rosefolly that fungus in a mulch is no cause for concern. Most fungi are decay organisms that help the world go 'round. I saw some of those white fibers just yesterday.

FWIW, someone told me a few years ago that the fallen leaves of the "California" Pepper Tree will retard the growth of other plants. I don't know this to be true, but you might want to consider it.

FWIW, the leaf litter of these trees IS mildly toxic, and would cause some intestinal distress to, say, a dog that ate any of it.

I love those trees, tho. Lovely, gracious trees. We planted two of them to make a screen between us and a neighboring house, and they've done the job well. They remind me of the trees that grew near my grandparents house, and I remember walking barefoot through the dusty ground under them, and the feel of the hard little fruits under my bare feet. A happy memory.

Jeri

Oak root fungus would be bad, because that will kill off roses. Otherwise, not a problem.

I get white stuff in my mulch all the time. I agree, it is no big deal...

Oh you wonderful people, you have no idea how relieved I am. Rosefolly, I saw what I now know to be be slime mold last years in just a small area and was totally grossed out. Nice to know that it too is not harmful although I don't care if I never see it again.

Jeri, I wonder if the toxins may break down if the leaves have been decomposing for several years since in many instances the roses have put out new growth very quickly after applying the mulch. It's so broken down that you can't discern at all that these were once leaves.

When the pepper trees are blooming, as they are now, you can hear the buzz of thousands of bees and for me that's enough reason to keep them, plus the fact that they require no water whatsoever, and grow rather quickly in spite of that.

Thank you all so much for the prompt responses; it meant a lot to me since I was really worried.

Ingrid

The California Pepper berries were once used as condiments until they determined they were toxic in any quantity. The coyotes LOVE them, but they're like 16 year old boys, omnivorous.

I've also heard they are allelopathic, though I'd bet a good portion of the apparent allelopathy is due to the invasive, extensive root system sucking everything from the soil and the GENEROUS, COPIUS litter it graces everything around it with.

These and the Brazillian Peppers are far enough from the planting areas here to not provide any real issues, other than BAZILLIANS of seedlings. The California Black Walnut that covers most of the level area where I can grow roses is more of an issue. Oh, well, I'll enjoy them while I can, before the wildlife take care of them all for me! Kim

Also, they cast a lot of shade, which may be a problem for some plants.

The Brasillian Peppers, tho -- I gather that those are very very invasive.

Did you know that all of the "California" peppers are SAID to have originated with a handful of seeds given to the padres at Mission San Luis Rey by a visiting sea captain, as a "dinner gift"?

I don't know whether that's true or not, but it's a nice story in any case.

Jeri

Well Jeri, you've "forced" me to look up pepper trees. It seems we have the California variety and fortunately they're planted away from the areas I garden. They're originally from Peru it seems. It's the Brazilian pepper tree that is very invasive and also more messy. We did cut down one near the driveway because it would have shaded some roses but have about five others, all fortunately well-sited in the "wild" areas of the property. The bees love them, the rabbits enjoy their shade, and they can be allowed to grow as large as they want to.

Ingrid

As stated, it depends on whether you have a fungus merely decomposing the litter or if all or part of the growth consists of oak root fungus (Armillaria). The problem with that one is that it does not always wait for wood encountered during its spread to be dead first - due to other causes - and may make its own wood to decompose by killing live shrubs and trees near the ground level.

A single Armillaria may in time come to occupy acreage. Large circular groupings of dead trees in forested areas hint at its presence.

Yes, armillaria is definitely a bad fungus, and there's not much a home gardener can do about it. A former member of this forum (Susan from Santa Barbara) had a bad infestation of it. The last I heard from her some years ago she was trying to decide if she should just grow all her roses in pots.

Here are is a link below with pictures. You can google for more information.

Here is a link that might be useful: Oak root fungus (armillaria)

Congratulations on the pepper trees Ingrid. I really do love them.
And I hope your fungus isn't armillaria, and can be ignored. (Which is most probable, I think.)

Jeri