You can get different types of mulch; wood chip, hay or grass clippings, or composted matter. For long term water-saving benefits our wood chip mulch is the best possible kind because you can apply it in a thick layer – about 6 cm deep – which will keep moisture in your garden beds. It is for this reason that wood chip mulch is the best kind for the garden. If you were to use grass clippings, compost or another type of mulch with pieces small enough to fit through a 5mm sieve, you should only apply it in a 2cm layer. If it is applied too thickly, mulch with fine fragments will prevent water from getting down into the soil because the mulch itself will soak up a lot of water. And when it dries out, this fine mulch will start to absorb moisture out of the soil beneath it. This means that your plants are only being robbed of the water they need to grow, instead of protected from the drying sun. Moreover, the plants’ roots may start to grow up into this damp mulch instead of down into the earth, leaving them with no strong root system and not much chance of survival once the mulch has decomposed.
Because wood chip mulch is made of large fragments you don’t have to worry about it absorbing water from the soil, or preventing rain from getting through. It will take many years for wood chip mulch to break down into the soil. Once you notice it starting to get a bit thin, you can fold it into the soil, or just add more wood chip mulch on top. Perhaps by then one of your trees will need a bit of maintenance, and the cycle can start over again. Cycles like this are a part of nature.