During the late summer and early fall, the interior needles of many
narrow-leaf evergreens (pine, spruce, etc.) turn yellow or brown and finally
drop off the plant. It’s not unusual to find entire neighborhoods or an entire
windbreak with pine needles dropping simultaneously.
While alarming, this is normal evergreen behavior for the late summer and
fall period. Evergreens shed their leaves like deciduous plants, but don’t
drop all of them every year. Ponderosa, Austrian and Scotch pines drop
3-year-old needles every year. Spruce drop their older needles on a 3 to 5 year
cycle.
Sometimes the process is slow and not very noticeable. Other times the needle
drop happens quickly. Adverse growing conditions in the summer or fall can make
the needle drop more evident.
As long as only the interior needles are shed in the late summer or fall, it
is normal; similar plant behavior at other times of the year is not normal and
should be investigated to determine the cause.
