The Oaks: genus Quercus

The oak trees constitute the genus Quercus. There are over a dozen species of native oaks growing wild in eastern Massachusetts, and as many again cultivated here. Some oaks are readily identified and recognized, such as Quercus alba, others such as Q. velutina are quite difficult to identify. Some oaks hybridize, further confusing matters. Although Red Oaks are common in moist mature woods containing beech, sugar maple and hemlocks, most oaks growing in the area are typical of dry conditions, often in young woods. Only Q. bicolor favors wet conditions. Oaks divide into two groups, termed the White Oaks and the Red Oaks. The White Oaks have rounded lobes to their leaves, and their acorns take two years to mature. The species in the Red Oak group (more numerous in our area), have sharp-tipped lobes, terminating with a bristle, and their fruits mature in a single year. The fruit of the oak is the acorn, a nut ranging from a couple of centimeters in length to more than four cm. long. The identifying feature of the acorn, is the (usually dehiscent) cup at the base. Some acorn cups enclose most of the fruit, others are mere saucers attached only to the base of the fruit. Among the commonest oaks are the White Oak, Quercus alba, the Red Oak, Quercus rubra, and the shrubby scrub oak, Quercus ilicifolia, which is usually less than chest high. The Black Oak Quercus velutina closely resembles Q. rubra and the Scarlet Oak, Q. coccinea. Quercus bicolor, swamp White Oak, commonly grows in wet places, and Q. palustris is commonly planted as a street tree. Of the above, all but Q. alba and Q. bicolor are in the Red Oak group.
Scientific Name: Quercus alba (QUAIRK·us AL·buh) "White Oak"
Common Name: White Oak
Family: Fagaceae (fayGAY·see·ee)
Bark: Light gray, with vertically elongate scales when young, in old age becomes blocky.
Buds: Smaller than those of other oaks, 4-5 mm long, ovoid and somewhat pointed. A warm medium brown. Twigs end in cluster of typically four buds.
Distinctive characteristics: Bark (on old trees, look at upper branches for the telltale scales), leaves.
Distribution: Native to area. Very common in wild. Slow growing and hard to transplant, thus specimens in cultivated areas have probably not been planted, but are the leftovers of woodland.
Flowers:
Fruit: Narrow acorn (a nut), with thin shelled cup, long peduncle.
Habit: In open spaces, spreading, with massive limbs, and (relatively short) heavy trunk. The most massive tree around. In woods, like all trees of the upper story, tall with a long trunk free of branches.
Habitat: Woods, parks, suburban lawns and roadsides.
Leaves: Alternate, with pinnate rounded lobes. 10-20 cm. long, plus 2 cm. petiole. Light green, smooth, thin (compared to other oaks'). Turning maroon to dull red in autumn. Slow to fall in winter.
Similar trees: Swamp White Oak has similar fruit.
Twigs: Slender, purplish, turning ashy. Scattered tan lenticels.
Scientific Name: Quercus cerris (QUAIRK·us SERR·us)
Common Name: Turkey Oak
Family: Fagaceae
Bark: Blocky, often with a characteristic extruded vertical ridge or two near base.
Buds:
Distinctive characteristics: Acorn cup and leaves will identify this tree for certain.
Distribution: Introduced. Planted near Harvard Law School in Cambridge, to the west of the Griswold Building.
Flowers:
Fruit: Acorn 3-4 cm. long, 1.5-2 cm. in diameter. Sessile. Green with yellow base where cup covered it. Often assymetrical in shape. Cup 1 cm. deep, with curly sea anemone-like tentacles all over it, increasing its diameter to over 3 cm. Cup is very distinctive.
Habit: Medium-sized to large tree, with smaller branches than some of the potentially more massive oaks like the Q. rubra and Q. alba.
Habitat: In cultivation.
Leaves: Petiole .5 inch. Leaf 3" long, 1" wide, with deep, irregular sinuses. A very narrow, small oak leaf. No northern, native oak has such small leaves.
Similar trees: Black oak has rather similar bark, without the excrescent ridges.
Twigs:
Scientific Name: Quercus ilicifolia (QUAIRK-us ill·ISS·a-FOE-lee-yuh) "Holly-leaved oak"
Common Name: Scrub Oak, Bear Oak.
Family: Fagaceae (fay-GAY-see-ee)
Bark:
Buds:
Distinctive characteristics: Leaves, size.
Distribution: Native, common in the right habitat. Not cultivated.
Flowers:
Fruit: A small acorn, with a shallow but relatively wide cup, firmly attached to nut. Nut is 1 cm long, relatively attenuate at tip, with paler longitudinal striations. Cup is 15 mm wide, and strongly made. Fruits are sessile in pairs on very short lateral twigs.
Habit: A crappy little bush of a tree. If you can't see over its top, you're kneeling.
Habitat: Rocky, open areas in dry woodland.
Leaves: Dark green above, white wooly below. Petiole 5 mm, leaf 7 or 8 cm. long, oblong, with irregular lobes.
Similar trees: None, except perhaps for stunted oaks in windswept locations.
Twigs:
Scientific Name: Quercus robur
Common Name: English Oak, Truffle Oak, Pedunculate Oak
Family: Fagaceae
Bark: Dark, with intersecting ridges, different from most oaks'.
Buds: Pentagonal in cross section, .25" long, plump, hairy fringe on scale edges.
Distinctive characteristics: Peduncle quite long.
Distribution: Introduced.
Flowers:
Fruit: An acorn. Oblong, brown, 1" by 3/4". Cup shallow, .25 of height of fruit, fine textured scales (for an oak), pale grayish brown, thin
Habit:
Habitat: Parks and lawns.
Leaves: Alternate, toothless margin, with 5 or 6 pairs of lobes with sinuses reaching halfway to midrib. Base of leaf has twin earlobes extending down petiole an eight of an inch.
Similar trees:
Twigs: Shiny, slender, gray-brown.
Scientific Name: Quercus rubra (QUAIRK·us ROO·bruh) "Red Oak"
Common Name: Red Oak, Northern Red Oak
Family: Fagaceae (fay-GAY-see-ee)
Bark: Smooth and dark brown-gray-green when young. Becomes blocky at base with maturity, and typically develops broad (1-2" wide) smooth longitudinal ridges or stripes on most of upper trunk.
Buds:
Distinctive characteristics: Bark, somewhat.
Distribution: Most common wild oak in area. Widely planted as landscape tree.
Flowers:
Fruit: Fat acorn, usually with very shallow cup, but not necessarily.
Habit: Smaller limbs than White Oak, often. A big, spreading tree.
Habitat: Any woods without soggy soil. Sometimes planted as a street tree in city, more often in parks, on lawns, or along suburban roads.
Leaves: Leathery, glossy, alternate, with pointy pinnate lobes.
Similar trees: Black Oak, Scarlet Oak, Pin Oak all have similar leaves. Use bark, acorns and habitat to separate. When in doubt, guess Red Oak. When you think you are looking at a Black Oak, guess Red Oak anyway. The only other widely planted city oak is Pin Oak, which has different bark, fruit and habit. In spite of what your friendly field guide says, with all its helpful pictures and thorough tables of leaf characteristics, avoid trying to identify Black, Red, Scarlet and Pin Oaks by their leaves: that way lies madness. (I will say this, for you gluttons for punishment: Red Oaks do typically have larger, duller, more regular leaves than Pin, Black and Scarlet Oaks. But not always, particularly in open sunny locations.)
Twigs:
Scientific Name: Quercus velutina (QUAIRK·us vel·OO·tin·uh) "velvety oak"
Common Name: Black Oak.
Family: Fagaceae (fay-GAY-see-ee)
Bark: Dark, blocky when old, smooth grey when young. Expect Black Oaks to lack the stripes of Red Oak.
Buds: 7-9 mm. long, pentagonal in cross section, covered with rusty wool.
Distinctive characteristics:
Distribution: Not cultivated (on purpose). Throughout eastern Massachusetts, extremely common, but probably less so than Red Oak. Hybridizes with Red Oak (yeah, you didn't want to hear that!)
Flowers:
Fruit: A nut (acorn), chestnut brown when ripe, sometimes with longitudinal dark stripes. Almost half-enclosed in cup. Cup has pale, silky hair lining it (you may have to break it open and use a hand lens). The scales on the cup have their upper edges loose, forming a fringe about the rim of the cup. The almost sessile fruit is 3 cm. long. The acorn is elliptical, 2 cm. long, by 1.5 cm. in diameter, the cup 2 cm. in diameter.
Habit: A big tree.
Habitat: Dry woods.
Leaves:
Similar trees: Scarlet and Red Oaks look like it. A lot. Use fruits and buds, not leaves, to distinguish them.
Twigs: Red-brown, slender, with tiny pale glandular speckles.

The Buckthorns: genus Rhamnus


Scientific Name: Rhamnus cathartica (RAM-nuss cah-THAR-tick-uh)
Common Name: Buckthorn
Family: Rhamnaceae
Bark: Dark grey, with lenticels.
Buds: Purple-brown, pointed, appressed to twig, .5 cm. long.
Distinctive Characteristics: Terminal thorn on the twigs, the black drupes on last year's growth, the serrate, elliptical, opposite and subopposite leaves.
Distribution: All over Massachusetts. Of European origin.
Flowers: Greenish and crappy.
Fruit: A black drupe, 5 mm in diameter on longish peduncles, borne on last year's growth.
Habit: Shrubby to small tree. Kinda gnarly. Not handsome.
Habitat: A weedy tree of waste places, roadsides. Seeds are spread by birds.
Leaves: Opposite, sometimes alternate, serrate, elliptical, with more or less attenuate tip and base, 1.5-2" long, 2-3 cm. broad, glaucous. .5" petiole. Curving veins rather like those of Cornus and Pyrus malus.
Similar trees Easy to recognize, less so to identify. Leaves are a bit apple-like, bark is cherryish.
Twigs: Tipped with small thorns. Grey, lightly ridged longitudinally.

The Black Locust: genus Robinia

Scientific Name: Robinia pseudoacacia (roe·BIN·ee·uh pseudo·uh·KAY·shuh)
Common Name: Black locust.
Family: Fabaceae (fay·BAY·see·ee)
Bark: Light to medium brown (despite name), deeply ridged, rough. Young trees (less than 5 inches d.b.h.) may still have spines on bark.
Buds:
Distinctive Characteristics: Only elms ever have bark like this tree. Flowers are distinctive, as are spines.
Distribution: Native to Ohio Valley, cultivated, mostly as weed or escape. One of the few introduced trees (along with Scotch Pine, Pinus sylvestris) that occasionally grows in woods. On Cape Cod, this tree has been widely planted, and could be taken for a native tree.
Flowers: Pea-like, white, hanging in bunches. Fragrant. June.
Fruit: A papery pod, about 4 inches long.
Habit: Upright tree, with rising branches, often quite large.
Habitat: Dry areas, usually waste places or sometimes in woods. Cultivated, but far less commonly than its cousin the Honey Locust (Gleditsia triacanthos).
Leaves: Alternate, pinnately-compound. Leaflets entire, oblong, 5-6 cm. long, and 2-3 cm. wide, rounded at base and tip. 11 to 25 leaflets per leaf. Autumn color, when present, yellow.
Similar trees Bark is elmy.
Twigs: The green twigs bear paired spines 5 mm. or longer at the leaf bases. The spines often persist and darken as the wood ages. The new twigs are fluted and bear a sprinkling of small tan lenticels.
Copyright © 1989, 1997, 2005 Brian Laurence Hughes
Last modified: 2005 Mar 19 at 20:32 EST

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