The archetypal oak grows large and spreads wide, with muscular, near-horizontal lower branches that seem to defy gravity. But the group’s 500 species, all native to the Northern Hemisphere, also include upright, pyramidal, and shrubby oaks; in fact, “chaparral” comes from chaparra—Spanish for a dwarf evergreen shrub oak. Oak leaves can be deciduous or evergreen (the latter are called live oaks); lobed, toothed, or smooth edged; but they’re always arranged in an alternate pattern along stems. Some have terrific fall color. All oaks produce inconspicuous flowers followed by acorns, whose single nuts have cuplike caps covered with closely set scales. Some kinds of acorns are edible and sweet, while others are bitter and unpalatable.
Oaks come in two broad categories: white oaks have acorns that mature during the season in which they are produced, and often have leaves with rounded lobes; red and black oaks have acorns that take two seasons to mature, and often have leaves with pointed lobes. Each group can hybridize only within itself.Quercus robur
This deciduous tree is native to Europe. It is a fairly fast grower to 50–60 ft. tall and 30 ft. wide, with a rather short trunk and very wide, open head. Dark green leaves have three to seven pairs of rounded lobes. Leaves hold until late fall without much color change. Acorns are to 1 1/2 in. long, varying in shape from oval to oblong, coming to an abrupt point; they are covered by up to one-third in a velvety, bowl-shaped cap. ‘Argenteamarginata’ has white-edged leaves, grows slowly to 20–30 ft.; narrow in youth. ‘Clemons’, a hybrid with Q. macrocarpa, grows about to 50 ft. tall and 40 ft. wide; has a little more cold tolerance than pure English oak. ‘Concordia’ grows about to 25 ft. tall and wide, with golden foliage. ‘Kindred Spirit’, a hybrid between columnar English oak and Q. bicolor, grows to 35 ft. tall and 6 ft. wide, with good disease resistance and tolerance to wet soil and drought. ‘Rosehill’—part English oak, part unknown species—grows to 40 ft. tall and 20 ft. wide, with glossy green, mildew-resistant foliage. ‘Skyrocket’ grows to about 45 ft. tall and 15 ft. wide, and holds its shape well. ‘Skymaster’ becomes a broad pyramid to 50 ft. tall and half as wide. ‘Crimson Spire’, a hybrid with white oak (Q. alba), is another narrowly upright grower (to 45 ft. tall and 15 ft. wide); it has reddish fall color and good mildew resistance.
Q. r. fastigiata, upright English oak, is columnar like Lombardy poplar (Populus nigra ‘Italica’) when young, growing to 50 ft. tall and 15 ft. wide, then maturing to a broad, pyramidal shape. ‘Regal Prince’, similar in height but slightly wider, is a cross between Q. r. fastigiata and an oak from the southeastern U.S.; it’s adaptable and resistant to mildew.
Biennial or short-lived perennial. Variable, appearing in many garden forms. Bold, erect growth to 4 f...
This deciduous tree is native to Europe. It is a fairly fast grower to 50–60 ft. tall and 30 ft....
Purple colored flowers.