Quercus L.

Oaks

Ancient Latin name.

Deciduous, semi-deciduous or evergreen trees or occasionally shrubs. Hairs star-shaped when viewed under hand-lens or microscope. Leaves alternate, toothed, lobed or occasionally entire, the deciduous ones often brightly coloured in autumn. Flowers appearing before or with the leaves, unisexual but both sexes on the same tree. Male flowers pendulous and catkin-like; stamens 4-6(-12). Female flowers solitary or clustered in spikes in the leaf axils with 6 parts fused to the ovary. Ovary inferior, mostly 3-chambered (rarely 4-5), enclosed in a sheath of bracts that becomes the acorn cup. Styles as many as ovary chambers. Fruit a 1-seeded nut (acorn) maturing in 1 or 2 years partially enclosed in a cup of basal scales.

Mostly long-lived and often slow-growing trees that grow naturally in woodlands and on hillsides. Most cultivated species thrive in cooler climates with rich soils and it is here that the autumn leaf colour is most spectacular, although species from the Mediterranean and SW USA and Mexico will tolerate poor, dry soils. Recent interest has centred on evergreen species such as those from Mexico. In SE Australia oaks are used largely as ornamental landscape trees for large parks, gardens, golf courses and also as street trees. Several of the cool-temperate species grow more quickly in the relatively warm SE Australian climate than they would in nature and sometimes naturally deciduous trees are only partially deciduous in Victoria e.g. Q. canariensis. Flowering occurs in spring for a brief period when the drooping male catkins adapted to wind pollination appear. Some are fragrant and pollinated by insects, possibly the ancient condition. In some cases several decades of growth are needed before the acorns are produced.

Rarely cultivated species include the following: Q. acuta Al. Murray, in Victoria at Belgrave 'Glen Harrow'-a multistemmed specimen 20 m tall with an 8 m canopy. Q. douglasii Hook. & Arn., Blue Oak, at Kyneton Botanic Gardens, Victoria - a fine old specimen tree in the Caravan Park area S of the residence. Q. kelloggii Newb., Californian Black Oak, Q. imbricaria Michx., Shingle Oak, and Q. falcata Michx. var. pagodifolia Elliot, Cherrybark Oak, are being trialled by Melbourne City Council for use as street trees. Q. phellos L., Willow Oak of SE USA has narrow, entire leaves and many mature specimens occur in Linnaeus Avenue on the Australian National University Campus, Canberra. A range of species has been used as street trees in O'Connor: these include Q. douglasii Hook. & Arn. in Lobelia St, Q. engelmannii Greene, Engelmann Oak, in Caladenia St, and Q. lobata Née, California White Oak in Clianthus St. Q. phillyreoides A. Gray, Ubame Oak, can be seen at the Royal Botanic Gardens Victoria (Melbourne Gardens) and 'Glenara' at Bulla. Q. rugosa (Masam.) J.C. Liao, Mexican Evergreen Oak can be seen at St Vincent Gardens, Albert Park; it was planted as a commemorative tree 23.7.1966.

The genus is generally divided into 2 subgenera. The subgenus Quercus includes all the familiar cultivated oaks and is further divided on the structure of the flowers and acorn cups. The subgenus Cyclobalanopsis is Asian and characterised by acorn cup scales that form distinctive concentric whorls. Classifications based on leaf size and margin outline are not believed to reflect natural groupings and are therefore not used in formal classification schemes. Within the subgenus Quercus distinction is often made between Erythrobalanus oaks with acorn scales tightly pressed down and the cup interior hairy, and the Lepidobalanus oaks with scales sometimes widely spread and the inside of the cups usually hairless. There are several loose practical groupings based on leaf types:

White Oaks have pale bark and leaves pale green to bluish, turning brown to orange in autumn e.g. Q. alba, Q. bicolor.

Black Oaks have leaves widest above the middle, entire or with a few lobes at the tip e.g. Q. nigra.

Scarlet Oaks have leaves with sinuate lobes and bristly teeth e.g. Q. palustris, Q. velutina.

Cork Oaks have evergreen leaves and corky barks e.g. Q. הhispanica, Q. suber.

Holly Oaks have evergreen thorny or entire leaves e.g. Q. ilex.

Turkey Oaks have mostly toothed leaves with slightly bristly or hard pointed tips to the teeth e.g. Q. castaneifolia, Q. cerris.

 

Diseases Microsphaera alphitoides, Oak Mildew, occurs on trees in mostly humid areas. In late spring small brown spots turn white, the area spreading over the leaf and distorting new leaves and shoots. Oak Leaf miner is widespread on soft leaves especially Q. robur, producing translucent lines and dots across the leaf surface in late season.

By seed (acorn) although these are very short-lived and should be planted immediately they are shed. Oaks are also notorious for hybridisation so acorns collected where several different species are grown together may not grow true to type. Cultivars and usually sterile hybrids are generally grafted on Q. robur stocks. Acorns are distributed among members of the International Dendrological Society.

A good example of historical hybridization is found in the Royal Botanic Gardens Victoria. In 1857 a Scot, Emanuel Sous, a mechanic working in the Melbourne Botanic Gardens (whose two sons also work in the Gardens) planted an acorn, collected on a plantation near Bothwell Castle, on the Princes Lawn. At 74 years old in 1931 the Gardens Curator Frederick Rae considered it to be in decline (Adapted from an article in The Argus Friday 23 January 1931). Bothwell Castle figures in the history of English-Scottish relations. In 1567 Mary (Queen of Scots) was married, with Protestant rites, to the 4th Earl of Bothwell, her fourth and final husband. The tree lasted several decades more before succumbing, but a new tree was grown from its acorns and also planted in the Princes Lawn where it thrives today (2018). It has variously shaped leaves with a felt of hair below, and large stalkless acorns with swollen scales at the base of the cups. It most closely resembles Q. alba but is probably a fertile hybrid.

Many of the oaks are important timber trees; in England, for example, the hard, durable wood was once widely used for ship contruction, furniture, pannelling etc.; acorns are used as pig food and as the source of tanning agents; bark extracts are used as dyes and as a source of tannins; commercial cork is the bark of Q. suber; galls (oak apples) are the source of tanning agents; leaves are used for feeding silkworms.

Male flowers in long, drooping catkins; leaves are generally characteristically lobed or toothed; the fruits (acorns) have a distinctive cup-like base, the acorn cup, that holds the acorn.

SA: There are 2 substantial collections in Adelaide - at the Mt Lofty Botanic Garden (possibly more than 60 species), and the Waite Research Institute of The University of Adelaide (about 30 species in 1989, specialising in evergreen Californian oaks introduced by Professor J. A. Prescott, second Director of the Institute, and Professor L. D. Pryor of Canberra). QLD: A collection at Laurel Bank Park, Toowoomba. NSW: Jackson Park, Faulconbridge, in the Blue Mountains is a commemorative avenue of oaks planted by or on behalf of all Australia's Prime Ministers. ACT: There is a range of species in Dunrossil Drive at the entrance to Yarralumla. VIC: Camperdown ( Camperdown Botanic Gardens); Castlemaine (Castlemaine Botanical Gardens, 10 species); Dunkeld (on 'Mereweather Arboretum', property of Mr Bill Funk who also collects the related species Lithocarpus and Castanopsis, 130 taxa of Quercus in 1994); Harcourt (N slope of Mt Alexander near the TV tower, indicated on maps of 1910, possibly an experimental commercial planting but now a dense plantation of 4-5 species); Kyneton (Kyneton Botanic Gardens); Leongatha (Mossvale Park, here there are many mature trees planted before and at the turn of the century around the old Moss Vale nursery site); Melbourne (Royal Bot. Gds, Oak Lawn, about 30 taxa, the older specimens of this collection were established about 1878 by Director William Guilfoyle); Burwood (Shade of Trees Nursery, Summit Road, proprietor Nicholas Edquist specialising in oaks); Ballarat Botanical Gardens and Geelong Botanic Gardens are both developing small oak collections obtaining specimens from Leonard Stubbs of East-West Road Warrigal: he had about 70 species in 1990 (although young), grown from acorns collected in the wild; Swan Reach (Tambo River), a small collection of George Haydn. NEW ZEALAND: The Hackfalls Arboretum at Tiniroto (curator Bob Berry), c. 20 km from Gisborne covers 22 ha with nearly 200 oak taxa assembled since 1924 and now specialises in Mexican species.

About 530 species from the temperate northern hemisphere (China, India, W Asia, Mediterranean, Europe) and the montane tropics (S and C America, also SE Asia).

Trelease (1924), Camus (1934-54), Palmer (1948), Bean (1976b), Miller & Lamb (1985), McArdle & Santamour (1985, 1987a, 1987b), Cullen & Maxwell (1989).

This is based mostly on the shape and size of leaves, and their degree of hairiness, also the shape and size of acorns and the structure of their cups. Seedling, juvenile, sucker and epicormic leaves are often atypical in size or shape and should not be used for identification. Acorns are generally borne in the period Jan-Mar. Identification is complicated by extensive hybridisation.

Source: Spencer, R. (1997). Fagaceae. In: Spencer, R.. Horticultural Flora of South-eastern Australia. Volume 2. Flowering plants. Dicotyledons. Part 1. The identification of garden and cultivated plants. University of New South Wales Press.

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kingdom Plantae
phylum   Tracheophyta
class    Magnoliopsida
superorder     Rosanae
order      Fagales
family       Fagaceae
Higher taxa
Subordinate taxa
species         Quercus acutissima Carruth.
species         Quercus agrifolia Née
species         Quercus alba L.
species         Quercus bicolor Willd.
species         Quercus canariensis Willd.
species         Quercus castaneifolia C.A.Mey.
species         Quercus cerris L.
species         Quercus coccifera
species         Quercus coccinea M ünchh.
species         Quercus dentata Thunb.
species         Quercus faginea Lam.
species         Quercus frainetto Ten.
species         Quercus ×hispanica Lam.
species         Quercus ilex L.
species         Quercus 'Macedon'
species         Quercus macrocarpa Michx.
species         Quercus montana
species         Quercus nigra L.
species         Quercus oblongata
species         Quercus palustris M ünchh.
species         Quercus petraea (Matt.) Liebl.
species         Quercus pubescens Willd.
species         Quercus robur L.
species         Quercus rubra L.
species         Quercus stellata Wangenh.
species         Quercus suber L.
species         Quercus velutina Lam.