Mulch does more than make beds look finished. It holds moisture in through dry stretches, keeps weeds down, and protects roots from the freeze-thaw swings common in the mountains.
The best time for a full refresh is mid-spring, once the soil has warmed up. Mulching too early keeps the ground cold and slows plants down. A lighter top-up in fall helps insulate roots for winter.
Depth matters. Two to three inches is enough. Piling mulch higher, especially in a cone against tree trunks, traps moisture against the bark and invites rot and pests. Keep mulch pulled back a few inches from trunks and from your siding.
Hardwood mulch breaks down and feeds the soil. Pine bark lasts a little longer. Pine straw stays put on steep slopes, which makes it a good choice on hillsides where shredded mulch washes out in a storm.
Before mulch goes down, beds should be weeded and edged. A clean spade-cut edge keeps mulch in the bed and out of the lawn, and it's what makes the job look sharp from the street.