Hi @lindasjohn . The main way that mulch suppresses weeds is by preventing sunlight from penetrating the top part of the soil. Sunlight triggers weed seeds to germinate, but if you keep them in the dark they don't get a chance to grow.
So almost anything can work as a mulch, from pebbles to shredded paper, as long as it's keeping sunlight out of the soil.
There can be benefits to using different mulches for different parts of your garden. To make your ornamental garden beds look their best you might want dark or red woodchips so that your flowers or greenery really pop. But on new plantings and vegetable gardens you might want to use lucerne mulch, which breaks down relatively quickly, providing extra nutrients to the soil.
If you live in an area where termites are a problem, you might want to use cypress mulch, which is said to discourage termites. You might also want to use pebbles or scoria as mulch up against your house, so there is no wood on the ground to attract termites.
In the past I've also used newspapers and cardboard under other mulches, but I've personally gone off that now because I've come to think of it as a barrier to water entering the soil, and to the soil breathing and functioning normally. But maybe that's just me.
In the end you might find it's not a case of one size fits all. It might be about looking at the different needs of the different parts of your garden and maybe using a couple of different mulches. Spread it thick to keep the light out of the soil, but don't pile it around the trunks of trees and stems of plants because it can retain moisture and cause them to rot.
I hope that helps. I'm sure other members will be able to add their own knowledge and experience too. Do let us know if you have more questions.
Cheers,
Brad
