Quercus laurifolia (Swamp laurel oak, Diamond-leaf oak, Water oak, Obtusa oak) is a medium sized deciduous or semi-evergreen oak in the red oak section Quercus sect. Lobatae. It is native to the southeast of the United States, from coastal Virginia to central Florida and as far west as southeast Texas.
It is a tree growing to 65-80 feet (20-25 m) (rarely to 130 feet (40 m)) tall, with a large, circular crown. The leaves are broad lanceolate, 1-5 in (3-12 cm) long and 0.5-1.75 in (1.5-4.5 cm) broad, and unlobed (very rarely three-lobed) with an entire margin and a bristle tip; they typically fall just as the new leaves start to emerge in spring. The acorns, borne in a shallow cup, are hemispherical, 0.35-0.5 in (9-12 mm) long, green, maturing blackish-brown about 18 months after pollination. Despite their bitter kernel, they are eaten by deer, squirrels and birds. Acorn production is often heavy, enhancing the species' value for wildlife.
Swamp laurel oak grows rapidly and usually matures in about 50 years which has led to its wide use as an ornamental. It is host to the general oak-feeding insects but has no serious insect problems. Several species of Curculio weevils infest the acorns.
Some authors (Burke 1961, 1963) have suggested that Swamp Laurel Oak is of hybrid origin having been derived from Willow oak and Water oak and is not found outside the ranges of the two supposed parental species. This was based on an index from leaf-shape on seedlings grown from acorns. This theory has not achieved wide support, with most authors accepting it as a species (e.g. Flora of North America).
Known hybrids with Quercus laurifolia as one parent are with Q. falcata (Q × beaumontiana Sarg.), Q. incana (Q. × atlantica Ashe), and Q. marilandica (Q. × diversiloba Tharp ex A. Camus).
The range has average annual temperatures from 16° to 21°C (61° to 70°F). It can withstand extreme lows ranging from -1° to -18°C (30° to 0°F). Extreme highs range from 38° to 43°C (100° to 109°F).
It needs between 1250-1500 mm (49-59 inches) of rainfall a year. From 500-1000 mm (20-39 inches) of this is received during the growing season from April to September.