Flowering and Fruiting- Pin oak is monoecious; flowers appear at about the time the leaves develop in the spring. Staminate flowers are borne on aments that develop from buds formed in the leaf axils of the previous year, and pistillate flowers are borne on short stalks from the axils of current-year leaves. Pollination is by wind. Fruit is an acorn (nut) that matures at the end of the second growing season after flowering. Acorns are dispersed from September to early December.

Seed Production and Dissemination- Pin oak stands begin producing seed at about age 20, but open-grown trees may begin at ages as young as 15 years. During a 14-year period, production of mature acorns in 32- to 46- year-old pin oak stands in southeastern Missouri averaged 210,300/ha (85,100/acre) but varied yearly from 13,300 to 492,700/ha (5,400 to 99,400/acre). Poor acorn crops occurred at 3- to 4-year intervals. Insect infestation rates varied inversely with crop size and, over all years, averaged 26 percent. Pin oak acorns are dispersed by  squirrels, mice, blue jays, and woodpeckers.

Pin oak acorns submerged in cold water as long as 6 months were not damaged. This tolerance may be partly due to a thick, waxy coating on the pericarp that impedes water absorption. The acorns require stratification of 30 to 45 days at 0° to 5° C (32° to 41° F) to break dormancy, and germination of sound, stratified acorns averages about 68 percent .

Damaging Agents- although pin oak is very tolerant of dormantseason flooding, it is much less tolerant of growing-season flooding and trees may be injured or killed by intermittent growing-season flooding over several successive years. The trees can usually survive one growing season of continuous flooding but will be killed by continuous flooding over 2 or 3 consecutive years (2,4,10,22). Pin oak is rated as "intermediately tolerant" to growing season flooding, along with such species as sugar maple (Acer saccharum), river birch (Betula nigra), southern red oak (Quercus falcata), and Shumard oak (Q. shumardii); it is less tolerant than red maple, silver maple, sweetgum, sycamore, swamp white oak, and American elm (tolerant) and eastern cottonwood, green ash, and black willow (very tolerant) (28,29). Dormant-season flooding for 20 years in a greentree reservoir in southeastern Missouri did not appear to damage pin oak trees, but did reduce stand basal area growth by 10 percent. However, in this same area approximately 5 years later (i.e., after 25 years of flooding), many, of these trees had developed bole swellings at and just above the average flood water level. These swellings caused longitudinal fissures in the bark up to 10 cm (4 in) wide, thereby exposing the bole xylem to decay organisms. The cause of this phenomenon is unknown, but it appears to be associated with the continuous dormant-season flooding, because pin oaks in adjacent areas subject only to intermittent natural flooding were not similarly affected.

The bark of pin oak is relatively thin and the species is therefore especially susceptible to damage by fire and the decay associated with fire wounds (12,22). Pin oak is subject to most of the diseases of oaks including oak wilt (Ceratocystis fagacearum) and is particularly susceptible to a leaf blister fungus (Taphrina caerulescens), a shoot-blight and twig canker fungus (Dothiorella quercina), and pin oak blight (Endothia gyrosa) (12). Pin oak is also host to many of the common oak-feeding insects including many defoliators, wood borers, gall wasps, and acorn weevils. Pin oak is classified as a "most preferred" host for gypsy moth (Lymantria dispar), and is also especially susceptible to the obscure scale (Melanaspis obscura), oak leaftier (Croesia semipurpurana), pin oak sawfly (Caliroa lineata), scarlet oak sawfly (C. quercuscoccineae), the sawfly Calinoa petiolata, the forest tent caterpillar (Malacosoma disstria), a leafroller (Argyrotaenia quercifoliana), the homed oak gall wasp (Callirhytis cornigera), and the gouty oak gall wasp (C. quercuspunctata). Thousands of acres of pin oak stands in southern Illinois have been severely damaged over the past 25 years by outbreaks of the horned oak gall wasp and the forest tent caterpillar.