CUISINE & CULTURE
Inner needles of conifers are dropping. Is the drying and dropping of conifer needles like pine, spruce and fir or the scale-like foliage of arborvitae a reason to be troubled?
Yellowing and dieback of needles at branch tips caused by insects, disease, or drought may be a reason to be concerned, but loss of inner needles is a natural, seasonal occurrence and is no cause for concern.
Just like deciduous trees that shed older leaves, the dropping of older, inner needles is a natural part of a conifer’s life cycle. Needle drop can accelerate if the tree is environmentally stressed but shedding of inner needles is normal.
Take a close look at the branches from tips to the trunk. The oldest needles closest to the trunk are those that will be shedding. They first lose color, turning yellowish-straw color and then to brown, before dropping to the ground.
Inner needles are not only the oldest, they are also those that have become shaded by the tree’s canopy. Foliage grows denser as branches grow and extend, limiting the photosynthetic capacity of the shaded inner needles. Needles that have been shaded will yellow as do the older needles and eventually die and drop off the branch.
Coniferous evergreens produce new and shed old foliage each year. Numbers of shed needles and scales vary by species. Pines differ from spruces and firs in how needles are attached to stems. Pine trees have fascicles (FAS-ihkulls) with needles that are grouped in bunches; typically, fascicles are composed of 2 to 5 needles, while spruces and firs have single needles that are attached to the stems.
Pine needles remain attached to stems for 3 to 5 years, while spruces and firs retain their needles for as many as 6 years before shedding.
Diagnosing if needles are dropping naturally can be done by looking at the texture of branch wood. The texture and color of stem tissue changes with age. As stem tissues age polymers of phenolic compounds are synthesized and produce lignin. Tissues darken and become tougher and are easily distinguished from tender, young, current season growth.
Gardeners look forward to the annual needle shedding, when conifers provide us with a plentiful source of natural organic mulch. Needles can be raked up and used as winter mulch or saved for the spring gardens.
Some information from awaytogarden.com; ccesuffolk. org
Ellen Peffley Harp, a retired professor of horticulture at Texas Tech University, writes about gardening for several Texas newspapers.
