I pile new mulch on top of old mulch.

Same here. The old mulch will break down and add organic matter to your soil.

I pick up the old mulch that other people throw out. I got a truckload today. :)

There is no real good reason to remove last years mulch to put new down, just spread the new mulch over the old. Some people will tell you that you need to because that old mulch may have some disease, something I have not seen.
An article in a recent issue of Organic Gardening magazine states that the research people at Texas A & M found that the "weed" blocker fabric can keep nutrients placed on top of the "weed" blocker fabric from getting into your soil.

The only reason to remove old mulch is if it hasn't been able to decompose properly. Sometimes, and I have seen this with all kinds of organic materials, fungal mycelium and hyphae will form a slick mat above the soil surface, impeding the healthy interaction between the soil SYSTEM and the mulch/atmosphere.

Using too much mulch is often the cause, or using a material that tends to lay down in a dense mat.

Stir up the old mulch a bit to make sure that this isn't happening but then you can reapply material in order to achieve a depth of 2 to 4 inches.

By the way, it would be worth your time to get rid of the weed fabric.

We use weed fabric in one particular garden because the weeds are absolutely terrible. We had the dirt brought in when we put the garden in. It's elevated about 8-12" in comparison to the area surrounding. We've had actual trees grow out of this soil and too many weeds to keep up with, no matter how much mulch we've put down. The weed fabric has done a good job of keeping the weeds under control. The main thing I want to know is should I remove the mulch that is sitting on top of this weed fabric? I don't believe it's decomposing. The mulch that we have on top of soil in our other gardens is decomposing, so I can see putting mulch right on top of that. It's the garden that we have the weed fabric on, I'm not sure what to do. Thanks!!!

What kind of mulches do you use? Are your other gardens using a different mulch? I've found a great mulch that I can just mix in to the soil in spring, fine pine mulch. It is finer than pine nuggets or evern mini nuggets. Its good ol' fine stuff and mixes easily. If you remove any just remove if you had put down too much. A lot of times we put down a whole lot right around winter time to protect the plants over winter. You might just remove the top layer and add fresh. But dont add too much just a couple of inches.

I always put new mulch on top of the old mulch.

IMHO
no
new on old is the best way (again IMHO)
ialbtc

I mulch every other year so I just spread it on top of the previous year's mulch.If you're just topping it off an inch or so is about all you need.

VERY helpful; informative. Thanks.

Weed fabric is the worst...it prevents plants from spreading out and also reproducing....cardboard is best as are grass clippings as a weed block

Arborist Scottie, that's way too much and unnecessary for such a simple question the OP asked. Books are reserved for hardback or softback, not gardening forums. JMHO.

>>Even stupider to trees continued health and public safety, Landscape trade presently approves of deeply edging around tree practice. Which blunderously severs and deflects all shallow roots

This is just downright hard to read, too. But extra points for 'blunderously', it's great even if it's not a real word. :-D

toxcrusadr, besides cramming parts of words that do not belong together. I line up common words that everyone is familiar with, just in a different order that no one had seen before. To embolden the most illiterate of folks! If only I had a secretary to proof read what my mind spews out, I would be golden!

Dirtguy50, I am afraid you are more than correct in that I answered a simple question with a thick Science book. My problem has always been, that I just don't know how much others already know about a subject. So I include the kitchen sink, to make sure the one thing someone may want to know...is covered.

It's a rare person who's not only aware of their limitations but freely talks about them! I'm just flat out annoying, myself. :-D

Blunderously! It’s a word! Very cool.

I appreciate the "science book" answers. Please don't assume everyone wants pablum.

We didn't, and I agree with you (as a scientist). It was really about the OP who did not know whether to remove last year's mulch before mulching. No offense to that person but pablum is perhaps appropriate in that case, so as not to present the questioner with overly complex answers.

I have a stretch across the front of the house that has very few plant, but weeds will sprout like crazy. The hubby insisted we needed weed fabric, then mulch. The mulch sat almost three years and mostly decomposed. I scooped it up and put it around my roses. I’m putting pine straw out on top of the fabric now..