If you are applying wood chip mulch to your garden – and we highly recommend that you do (read why here) – then you should apply a fertiliser to your garden before you layer the mulch on top. The reason that you want to apply a fertiliser beforehand is because mulch removes a bit of nitrogen out of the soil when it fresh and starting to break down. However, after this first stage it then begins to add nitrogen into the soil, so it is very beneficial to your garden in the long run.
If you have Australian native plants in your garden you should know that most natives don’t like too much potassium which is common in many fertilisers and natural sources such as chook poo. However, you can find fertilisers with low potassium so be sure to double check with your nursery when purchasing a fertiliser.
Another thing that you should do before applying wood chip mulch, or any kind of mulch, to your garden is to remove the majority of weeds, especially those that won’t mind continuing to grow in the mulch. Unfortunately weeds such as nut grass, couch grass, oxalis and wandering jew will not be controlled by the mulch.
It is also ideal to break up the surface of the soil a bit with a fork if it is very dry. Adding a wetting agent and giving it a good soak of water will also be very beneficial if you are able to. Spread the mulch around evenly, but leave at least 3 cm around the base of trees and other shrubs or else they might get too damp and suffer from various types of rot in the trunk.
Adding mulch to your garden is a good idea any time of the year since it helps your garden retain water, restrict the growth of weeds and adds valuable nutrients to the soil long term. However the best possible time of the year to mulch your garden is at the end of wet season, or start of the dry season. For most of Australia that is around April once the summer rains have stopped. The reason to add mulch to your garden at this time is that it will help hold in all that moisture the soil has collected for the dry months ahead.