It’s a good idea to use mulch for your garden for a variety of reasons that most gardeners will quickly point out. On the one hand, a properly selected and sized mulch bed will prevent moisture from escaping your soil too easily through evaporation. On the other hand, it can also shield sensitive seedlings from the sun and induce slow-release nutrients that will keep feeding the soil for a long time.
Now, depending on how you’ve chosen your mulch particles and how large they are, the amount of time they last can differ. If you want your mulch to last as long as possible – even up to three years – you, therefore, have to be very cautious about the size of the particles, the depth of the mulch bed and the materials you are using as most of it will turn in compost for plants and garden beds.
Grass clippings and shredded leaves might be great for feeding your soil, but they won’t last too long. As a result, you’re better off avoiding them and instead using a slow release fertilizer to feed your soil, while focusing on adding longer lasting mulch elements that won’t deteriorate so quickly.
The best idea is to go with chipped bark, straw and pine needles, and keep most particles at a generally uniform size. As they decay, they will therefore decompose in an even manner and over a longer period of time. Also, the depth of the bed should be relative to the size of the mulch particles, so avoid for example, making a shallow mulch bed out of particles that are 2-3 inches in size.