The answer to 'frequency of mulching' is that most experts recommend applying a fresh layer of mulch around your plants and trees 1-2 times per year. Mulch helps retain soil moisture, suppress weeds, and insulate plant roots from temperature extremes. The ideal time to mulch is in the spring before the growing season and again in the fall to protect plants over the winter.
The depth of the mulch layer is also important - aim for 2-4 inches of mulch around the base of plants, being careful not to let it touch the stems or trunks. Replenishing the mulch when it starts to decompose and thin out will ensure your plants continue to receive the benefits.