The answer to 'when to mulching' is that the best time to apply mulch is in the spring, typically between March and May. This helps retain moisture in the soil, suppress weeds, and insulate plant roots from temperature extremes. Mulch should be applied 2-4 inches deep around trees, shrubs, and other plants, keeping it a few inches away from the plant stems or tree trunks.
Mulching can also be done in the fall, after plants have gone dormant, to protect roots over the winter. However, spring is generally the ideal time for most homeowners to refresh their mulch and prepare their landscape for the growing season.