I like use different color pea gravel and peastone.

Very thick layer of shredded wood chips.

Almost any mulch will do the same thing regarding weed suppression - that is, much, but not all. Plus, weeds can seed onto the top.

The question is what your AFTER plan is. That is, will you or anyone else ever want to remove this? What will you do when this mulch needs to be renewed (and it always will)?

If you don't address these types of questions, you will be not quite solving a current problem while creating a long term headache IF YOU USE ANY MATERIAL THAT DOES NOT SIMPLY BIODEGRADE. Any organic mulch, wood chips, bark mulch, pine straw, etc - will simply break down and disappear, and renewal is easy. Non-organic, like stones or rubber, will need to be removed and with renewal, a thick layer will build up.

Stones are at least inert, although they are a removal headache and have other disadvantages. As for rubber, although many clever new uses for it are being devised to use up old tires, in my opinion mulch is not one of them.

Karin L

Frank,
As you might already know, mulch can serve several purposes .
Folks sometimes use it for just one or two reasons but there are several solutions that mulch address simultaneously.

The obvious reason why people choose mulch is to give the planting bed a 'finished' off look while suppressing weed growth .

Others apply a biodegradable organic mulch to stimulate a healthy soil , and a healthy soil means healthy plants. As the mulch breaks down it decomposes into the soil feeding all the micro organisms creating a nutrient rich soil.

Some install mulch with the main focus to conserve on water usage. The mulch layer keeps the soil from drying out too fast and so less irrigation water is required.

Parents and playground designers like to use a very thick layer of chipped cedar mulch as a safe playground surface , especially around playstructures , where it can absorb some shock from a fall.

What solution are you interested in addressing with a mulch covering ?
Water conservation ?
Enriching soil / improving soil health ?
Keeping weeds down ?
A kid friendly play surface ?
An bio-degradable path surface - like a woodland path ?

And as you have found out, there are different types of mulch mediums that serves different purposes : chipped, shredded and ground bark mulches, stone mulches, chipped recycled wood pallet mulch that has been dyed, recycled rubber tire mulch, pine straw mulch........ all have their virtues depending on how you plan to use them and for what reason.