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Quercus palustris

Pin Oak

(Fagaceae - Beech Family)

Form

• large shade tree
• maturing at about 100' tall by 40' wide when healthy under urban conditions, but even larger than that in the wild
• upright pyramidal growth habit in youth, becoming upright oval with age
• medium to rapid growth rate (most rapid in acidic, permanently moist soils)

Culture

• full sun to partial sun (partial shade tolerant in youth)
• performs best in full sun in continuously moist to wet, deep, very acidic soils, but is adaptable to dry soils; however, it is usually exacting in its need for soils with an acidic pH (optimally between pH 5.0 and 6.5)
• propagated by seeds
• Beech Family, with no serious diseases or pests, although foliage chlorosis is the symptom of the major physiological problem caused by a lack of iron (and nitrogen) uptake into the roots, due to the site soils being neutral to alkaline in their pH
• commonly available in ball and burlap form
• member of the Red Oak group; some of these members may hybridize freely in the wild, resulting in a blending of such traits as leaf shape and fruit size
• Pin Oak is rather sensitive to being transplanted in Autumn (even though compared to other Oaks, it has a relatively fibrous root system when young, which aids in root regeneration), and care should be taken to amend the soil, fertilize, water thoroughly, mulch adequately, and avoid Winter salt spray, to enhance survival chances during the first Winter, if transplanting cannot be delayed until Spring
• cultural treatment for foliage chlorosis (a symptom of systemic iron and nitrogen deficiency throughout the entire tree) includes soil acidification (a nearly impossible task on the grand scale and soil depth required), soil fertilization with chelated iron and other micronutrients (which is short-term help and good supplemental treatment with the third item below), or direct iron supplementation (iron sulfate or ferric ammonium citrate as pellets in capsule containers, deposited directly by boring into the sapwood of the tree trunk, which does work but needs to be repeated every three to five years)
• Pin Oaks are one of the best examples of the need of plant propagators to adhere, in the cases of plants with exacting evolutionary requirements, to the practice of provenance; Pin Oaks grown from a local seed source are always the best, since native Pin Oak trees (rather than those sprouted from the acorn source at a far-way seedling nursery) have adapted to the pH of the local soils; however, this is rarely done, unfortunately for economic reasons
• there is no "cultivar" of Pin Oak that has golden foliage; rather, this chlorotic affliction in non-acidic soils, coupled with the stunted growth of affected trees, renders this species subject to invasion by opportunistic pests and pathogens, dieback in Summer and Winter, and early death
• Pin Oaks get very dense in their branching even at a young age, and are optimally thinned out every five to ten years by arborists to allow light penetration to the interior canopy and ground below

Foliage

• medium- to dark green, alternate, with an overall shape that is ovate and about 5" long, with 3 to 7 prominent bristle-tipped, incised, and relatively thin lobes having very deep "U"-shaped sinuses in-between (the bristle tips identify it as belonging to the Red Oak Group)
• foliage may become chlorotic and small in high pH soils, with chartreuse to yellow leaf blades having green veins, due to poor iron uptake, which in turn prevents nitrogen uptake and "chlorophyll a" (green chlorophyll) assimilation
• fall color is usually an attractive red-brown to russet, but sometimes an outstanding crimson
• most of the dead leaves on young trees hang on throughout the Winter, creating the maintenance chore of their removal or "mower mulching" in the Spring when they abscise; mature trees lose most or all of their foliage by Winter, with only a few leaves in the lower interior canopy showing this residual juvenile trait

Flowers

• yellow-brown pendulous male catkins are obvious and prominent in late April, but are ornamentally insignificant, as are the very small pistillate flowers

Fruits

• mature in two seasons
• fruit is a small acorn (0.25" long) with a cap covering only the very top of the small nut, on a short peduncle and often in clusters of two or three

Twigs

• greenish- to reddish-brown, turning gray by the second year and somewhat thin
• Pin Oak is perhaps the most twiggy of all the Oaks, and retains dead limbs (due to self-shading) in its interior and lower canopy for many years unless they are thinned out

Trunk

• bark is medium gray, being lightly furrowed into middle age and beyond, and slowly becoming more deeply furrowed with a light reddish interior bark in old age
• branches are characteristically descending (angled sharply downward) on the lower one-third of the trunk, horizontal in the middle one-third, and ascending on the upper one-third, sometimes breaking into co-dominant central leaders by middle age
• branches arising directly from the trunk are numerous, thick, of relatively small caliper, and densely twiggy, adding to the medium texture of the tree in Winter
• wood is reddish-brown

ID Summary

• Pin Oak is virtually unique in its branching pattern; it has a strongly upright pyramidal growth habit in youth, to the point of being extremely dense, formal, and symmetrical; in addition, the lowermost branches are angled sharply downward, the middle branches are horizontal, and the upper branches are ascending
• branches are numerous from the trunk as compared to other Oaks, and as a result each tends to be of small caliper, rather narrow (as opposed to spreading) in its three-dimensional position in the canopy, and densely twiggy
• leaves are medium-sized for an oak and shiny dark green (or chartreuse to sickly yellow when chlorotic), with three to seven (usually five) lobes that are incised and bristle-tipped, having fall color that is usually red-brown, with foliage that is almost always persistent on all but the outermost branch tips of young trees throughout the Winter, then abscising in early Spring just before bud break
• Pin Oak leaves are sometimes confused with its close relative Scarlet Oak (Quercus coccinea), but the latter typically has one extra pair of lobes, with deep sinuses in a "C" shape, rather than a "U" shape; Pin Oak leaves may also be confused with those of Southern Red Oak (Quercus falcata), but the latter has a much-elongated terminal lobe and a pair of wide, forward-pointing basal lobes, rather than thin, spreading basal lobes
• fruits are small acorns that mature over a two-year period, with caps covering the upper quarter of the fruit

Function

• shade tree for dry, moist, or wet sites, especially where a stately and symmetrical growth habit in a large deciduous tree is needed (in this case an upright pyramidal form, with downswept lower branches)

Texture

• medium texture in foliage and when bare
• thick density in foliage and when bare

Assets

• formal pyramidal growth habit
• most easily transplanted Oak, due to a fibrous root system
• rapid growth and establishment (when in acidic pH soils)
• fall color is often russet-brown to crimson
• dry site or wet site tolerant
• urban tolerant (heat, drought, pollution, thin soils)
• fruits attract wildlife
• valuable timber tree

Liabilities

• leaf chlorosis and branch dieback when planted in high pH soils
• persistent dead foliage on the tree throughout Winter (for young and middle-aged trees, with the resulting leaf litter in Spring)
• fruit litter with age

Habitat

• zones 5 to 8
• native to the Eastern United States

Variants

• Quercus palustris 'Sovereign' - lower branches are horizontal to slightly downswept, instead of strongly downswept; this cultivar is not commonly available, and basically erases one of the most beautiful features of the species

Purpose

• Pin Oak has three noteworthy characteristics that render it important for study and propagation: (1) its overall form of strongly downswept lower branches, horizontal middle branches, and vertically ascending upper branches is unique among deciduous shade trees, (2) its strong tendency for life-threatening chlorosis in alkaline to neutral pH soils demonstrates the importance of local seed sources (provenance) for some landscape plants, and (3) its relatively fibrous root system makes it the Oak with the greatest success rate during post-transplant root regeneration and re-establishment.

Summary

• Quercus palustris is known as a very popular symmetrical shade tree that can tolerate dry or wet sites, with characteristic downswept lower branches and ascending upper branches, that when placed in the correct pH soils can grow very rapidly and ascend to great heights at maturity.

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