Sessile oak, Quercus petraea, Q. sessilifloraSee also Pedunculate oak Q. robur and Red oak Q. borealis. Sources of seed and plants Widespread in Britain but most common in south western England and Wales, Lake District and western Scotland, sometimes growing on sites over 400 metres elevation. The finest trees and stands are found on the Welsh borders. Acorns of Sessile oak must be collected from stands recorded in the National Register of Seed Sources under EEC rules. Silviculture A strongly light demanding and pioneer species, Sessile oak is often grown in mixture with larch, Norway spruce, beech, hornbeam, lime and sycamore. Such mixtures need constant attention to produce good crops of oak. Soil types Grows to the largest sizes on deep, porous, light-textured brown earths. Tolerates clay soils but timber quality suffers on sites with pronounced fluctuations of the water table. Rate of growth and yield Grows slowly at first and plastic shelters are being used to protect young trees and speed up early growth. Reaches 10 metres in 30 years and 20 metres in 70 years with stem diameters of 30 to 45 cms depending on thinning intensity. Isolating the crowns of' dominant trees greatly increases diameter growth. In well-tended stands the stems are straight and branches slant upward to form compact crowns. A long-lived tree which remains healthy for 400 years or more. Protection and resistance Oak mildew, caused by Microsphaera alphitoides must be controlled in the nursery. Tortrix viridana, the oak leaf roller moth, causes less defoliation on Sessile oak than Pedunculate oak. Liable to damage by late spring frosts on wet sites and frost cracks can appear on the stems of' older trees. Wind firm and tolerates exposure, so forms the backbone of shelterbelts. It is browsed by deer and damaged by grey squirrels. Establishing and tending All common sizes of planting stock establish well. Fruits at irregular intervals. Coppices strongly. Timber properties A ring-porous wood, yellowish brown in colour. The sapwood is light and distinct from the heartwood. Generally straight grained, the characteristic ornamental silver grain is due to broad medullary rays. Oak is strong (average 720 kg/m3 seasoned) and dries slowly with a marked tendency to split and crack. Clear timber is very good for bending and good for staining and polishing. The heartwood is durable and extremely resistant to preservatives. Amenity value A handsome and well-proportioned tree with a less spreading crown than Pedunculate oak. Conservation The oaks support 284 species of insects. The acorns are food for jays, mice, squirrels and deer. Timber value Good quality oak is used for furniture, panelling, high class joinery, decorative veneers and exterior work. It cleaves well and lower grades are used for fencing, gates and mining timber. All grades are used in boat building. Economic appraisal The site must be sufficiently fertile to allow the growth of straight trees, there must be regular tending to favour the best stems and the associated species in mixed crops must provide revenue while the oak is maturing. |
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