Evergreens provide green color all year long but that doesn’t mean that the individual needles live forever. Evergreens shed their older needles to make room for new growth, but what makes them evergreen is that they retain some foliage all year long instead of shedding all of the leaves at once.
Evergreen needles have varying life spans, depending on the species. Arborvitae and pine needles live for 2 years while spruce needles live 3-10 years. Some species of evergreens have a more noticeable leaf drop than others. In autumn, arborvitae and white pine will drop their 2-year old needles all at once, which can be quite alarming if you don’t realize that it’s perfectly normal.
On other species, needle drop occurs gradually with a small number of needles falling at one time. The older needles of yew shrubs will turn yellow and drop in late spring or early summer. Broad-leaved evergreens such as rhododendrons drop their 2- to 3-year-old leaves in late summer and early fall.
The hot, dry weather experienced over much of the region appears to be causing many plants to drop needles early. Inner and lower needles that are hidden from light are usually the first to drop. Pruning excess growth and dead limbs can help open the plant to more light. But for most plants, there’s no need to worry; they are just doing what comes naturally.