Evergreen needles don’t last forever, and some trees lose their needles every single year! If you have conifers in your landscape, I hope this information may save you from unnecessary alarm.
Dr. Rosie Lerner, the retired consumer horticulture specialist at Purdue University, wrote about this phenomenon. “Evergreens provide green color all year long, but that doesn’t mean that the individual needles live forever,” she said. “Evergreens shed their older needles to make room for new growth, but what makes these plants evergreen is that they retain some foliage all year long instead of shedding all of the leaves at once.”
Before we proceed further, let’s take a moment to understand tree terminology. Evergreens are plants that retain green foliage all year long. Mostly we think of needle evergreen trees, like pine, spruce, and fir as evergreens. Evergreen shrubs with needles include mugo pine and yew. However, we also have broadleaf evergreen shrubs, like rhododendron, boxwood, and holly. A conifer is a cone-bearing tree or shrub, although not all cones look like typical pine cones. Deciduous trees lose all their leaves or needles every year prior to winter. Examples of deciduous conifers include bald cypress, dawn redwood, and American larch (Tamarack). These trees regrow new needles every spring.
Evergreens like pine, spruce, fir, arborvitae, and hemlock only retain the newest years’ needles (2 or more years), and naturally lose their inner (oldest) needles on established trees each year.
“Conifer needles have varying life spans, depending on the species and environmental conditions,” said Lerner. “White pine and arborvitae needles live for 2-3 years, Austrian and Scots pine needles live for 3 years, red pine needles live for 4 years.” She said that firs, Douglas-fir, and hemlock needles last about 3-4 years. Spruce needles live 3-10 years depending on the species, with most lasting about 5 years.
Needle drop is not always in the fall season. “The older needles of yew shrubs will turn yellow and drop in late spring or early summer,” said Lerner. “Broad-leaved evergreens such as rhododendrons drop their 2- to 3-year-old leaves in late summer and early fall.”
While some species may exhibit gradual needle drop, two evergreens with a striking and alarming fall needle drop are white pine and arborvitae. Many homeowners confuse this normal annual occurrence with a plant disease, which can be upsetting.
“In autumn, white pine will drop many of their 2-year-old needles all at once, which can be quite alarming if you don’t realize that it’s perfectly normal,” said Lerner. “Arborvitae also has a very noticeable needle shed as older branchlets turn brown and remain on the tree for a while before shedding.”
Lerner said that hot, dry weather can cause many plants to drop needles early. Inner and lower needles are the oldest. “So, if your evergreens appear to be losing large numbers of needles, check to see if there is a uniform pattern of which needles are dropping,” she said. “And, if it is a white pine or arborvitae in autumn, they are most likely just doing what comes naturally.”
