Quercus palustris, the pin oak or swamp Spanish oak, is an oak in the red oak section Quercus sect. Lobatae. Pin Oak is one of the most commonly used landscaping oak in its native range due to its ease of transplant, relatively fast growth, and pollution tolerance. Its distinctive shape is considered unique among hardwoods.
Quercus palustris is mainly distributed in the eastern United States from Connecticut west to eastern Kansas, and south to Georgia, across to eastern Oklahoma; it is also native in the extreme south of Ontario, Canada. The pin oak is also well adapted to life in Australia (where it has been introduced) and is quite widespread across the Australian continent especially in the cooler southern States such as Victoria and New South Wales. Is also well adapted to life in Argentina, especially in the Río de la Plata region.
Pin oak grows primarily on level or nearly level, poorly drained alluvial floodplain and river bottom soils with high clay content. Pin oak is usually found on sites that flood intermittently during the dormant season but do not ordinarily flood during the growing season. It does not grow on the lowest, most poorly drained sites that may be covered with standing water through much of the growing season. However, it does grow extensively on poorly drained upland "pin oak flats" on the glacial till plains of southwestern Ohio, southern Illinois and Indiana, and northern Missouri. The level topography and presence of a claypan in the soil of these areas cause these sites to be excessively wet in winter and spring.
It is a medium-sized deciduous tree growing to 18–22 metres (59–72 ft) tall, with a trunk up to 1 metre (3.3 ft) diameter. It has an 8–14-metre (26–46 ft) spread. A 10-year-old tree will be about 8 metres (26 ft) tall. Young trees have a straight, columnar trunk with smooth bark and a pyramidal canopy. By the time the tree is 40 years old, it develops more rough bark with a loose, spreading canopy. This canopy is considered one of the most distinctive features of the pin oak: the upper branches point upwards, the middle branches are perpendicular to trunk, and the lower branches droop downards.
The leaves are 5–16 centimetres (2.0–6.3 in) long and 5–12 centimetres (2.0–4.7 in) broad, lobed, with five or seven lobes. Each lobe has 5-7 bristle-tipped teeth. The sinuses are typically u-shaped and extremely deep cut. In fact, there is approximately the same amount of sinus area as actual leaf area. The leaf is mostly hairless, except for a very characteristic tuft of pale orange-brown down on the lower surface where each lobe vein joins the central vein. Overall autumn leaf coloration is generally bronze, though individual leaves may be red for a time, and is not considered particularly distinctive. The acorns, borne in a shallow, thin cap, are hemispherical, 10–16 millimetres (0.39–0.63 in) long and 9–15 millimetres (0.35–0.59 in) broad, green maturing pale brown about 18 months after pollination. The acorn is unpalatable because the kernel is very bitter.
A fast-growing pioneer or riparian species, pin oak is relatively short-lived, with a maximum lifespan of 120 years against many oaks which can live several centuries. It is naturally a wetland tree, and develops a shallow, fibrous root system, unlike many oaks, which have a strong, deep taproot when young. It is confined to acidic soils, and does not tolerate limestone or sandy Florida soil, and grows at low altitudes from sea level up to 350 m (1,148 ft). The Latin specific epithet palustris means "of swamps".
A characteristic shared by a few other oak species, and also some beeches and hornbeams, is the retention of leaves through the winter on juvenile trees, a natural phenomenon referred to as marcescence. Young trees under 6 metres (20 ft) will often be covered with leaves year-round, though the leaves die in the fall, remaining attached to the shoots until the new leaves appear in the spring. As with many other oak species, dead pin oak branches will stay on the tree for many years.
Easily grown in average, medium to wet, acidic soils in full sun. Prefers moist loams. Tolerates poorly drained soils. Tolerates some flooding. May take up to 15-20 years for this tree to bear a first crop of acorns.
Quercus palustris commonly called pin oak is a medium sized deciduous oak of the red oak group that typically grows 50-70’ (less frequently to 100’) tall with a broad pyramidal crown. Upper branches are ascending, middle branches are somewhat horizontal and lower branches are descending. In the wild, the lower branches of this tree are often shaded by other trees, eventually dying and breaking off leaving persistent pin-like stubs, hence the common name. Trunk diameter to 3’. Smooth gray-brown bark usually develops ridging with age. This is a tree of lowlands and bottomlands that is primarily native to the Midwest and mid-Atlantic States. In Missouri, it typically occurs in valleys, floodplains and stream margins, but is infrequently found in drier upland areas (Steyermark). Insignificant monoecious yellowish-green flowers in separate male and female catkins appear in spring as the leaves emerge. Fruits are rounded acorns (to 1/2” long), with shallow, saucer-shaped acorn cups that barely cover the acorn base. Acorns are an important source of food for wildlife. Glossy, dark green leaves (to 5” long) typically have 5 bristle-tipped lobes with deeply cut sinuses extending close to the midrib. Leaves turn deep red in fall. Pin oak is pehaps the most popular commercial oak of eastern North America, having been widely planted as both a street and a landscape tree.
Genus name from Latin means oak.
Specific epithet comes from the Latin word for marsh (palus), in reference to a common habitat for this tree.
Chlorosis (yellowing of leaves) is common in alkaline soils and can severely damage this tree. Pin oak is otherwise infrequently attacked by the common diseases of oaks which include oak wilt, chestnut blight, shoestring root rot, anthracnose, oak leaf blister, cankers, leaf spots and powdery mildew. Potential insect pests include scale, oak skeletonizer, leaf miner, galls, oak lace bugs, borers, caterpillars and nut weevils.
A medium shade tree for lawns, streets or parks.