Leaf Identification
The Pin Oak has simple leaves alternately arranged on the stem, 3-6″ long. Each leaf has 5 or 7 pointed lobes with awns (bristles) at the tip. The sinuses between the lobes are deep and U-shaped. The leaf is widest halfway up, forming a diamond shape. The leaf is dark green on top with a pale green underside and hairy tufts at leaf vein axils underneath.
Twig and Bud Identification
The twig is brown and smooth with pale white lenticels (pores). The buds are reddish-brown and many-scaled, with medium hairs on the fringes of the upper scales. The terminal buds are clustered.
Bark Identification
The bark of the Pin Oak is gray and ridged, with occasional fissuring but no scales.
Fruit Identification
The Pin Oak acorn is distinctively wide and often striped, with a cup of thin, tan scales that can range from shallow to deep at the top of the acorn. The cup can persist on the stem even after the acorn detaches. This acorn is one of the smallest of the Midwestern oaks, only reaching 1/2″ in diameter.
Flower Identification
Pin Oak flowers are monoecious, with separate male and female flowers on the same tree. The staminate (male) flowers are yellow and on hanging catkins (long, slender clusters of flowers), and the pistillate (female) flowers are miniature, singular, green-red, and located at the leaf axil.