The surfaces of one-year-old twigs have well-developed woody needle bases that persist for many years after needle abscission. Early in development they are reddish-brown and later turn grayer. The color of the shoot depends upon the provenance. Lowland populations retain their brownish bark for long periods, whereas individuals from higher altitudes and from the far north exhibit grayer-colored bark.
Although the twigs are generally hairless, young shoots of northern provenances of the subspecies Picea obovata develop single- or multi-cellular hairs on the epidermis. These hairs typically persist for one year, but may be found on shoots up to three-years old. This trait appears to be largely genetic and has been used to distinguish subspecies and enabled the reconstruction of migration pathways of this species after the last ice age (LINDQUIST1948).
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