Lithocarpus glaber aka Japanese Oak

Lithocarpus glaber is an evergreen tree in the beech family, Fagaceae. Its common names include Japanese blue oak and ring-cupped oak. It comes from central and southern Japan, Taiwan, and southern China. It grows in mixed forests and on sunny slopes. In gardens, it forms a small tree or large shrub. Growth is slow, with an upright, oval or rounded shape. Some plants have more than one main stem.

Garden trees reach 20–30 feet [6.1–9.1 metres] tall. Their spread is about 10–15 feet [3–4.6 metres]. Young bark is smooth and dark brown to almost black. With age, it grows rough and develops deep grooves. The thick, stiff stems are dark olive green. Pale lenticels stand out against them. Brown scales cover the buds, and young shoots bear hairs.

The simple leaves feel firm and leathery. Their shape ranges from oval to oblong, with rounded bases. New leaves show bronze or purple shades in spring. By summer, their upper sides turn glossy dark green. Fine hairs cover the gray-green to blue-green undersides. Most leaf edges are smooth, with teeth near the tip. Fall tones are muted yellow-green, though the tree stays evergreen. Cold can harm the foliage.

Small yellow flowers appear in spring, in separate male and female catkins. Brown acorns follow in fall and draw wildlife. They grow alone or in groups of two or three. Each nut has a cup with five or six rings. This cup encloses about one-third of the acorn. The foliage and fruit suit a woodland or Asian-style garden. The tree also serves as a specimen or small shade tree. It can provide a screen or grow along a street. Deer may browse it, but it has some resistance.

Give this tree full sun for best growth. It accepts sand, loam, and clay, including soil that stays wet at times. Deep, fertile soil with drainage suits it well. Acid to neutral soil is suitable. Its listed hardiness range is USDA zones 8–9. The acorns are edible only after preparation removes their tannins. Soaking with fresh water changes or boiling can remove them. Raw acorns and young leaves can cause poisoning. Symptoms include stomach pain, constipation, and later bloody diarrhea. Excess thirst and urination may also occur. NC State rates the poison risk as low.