Tree for Life – Oak

Tree for Life – Oak:
We decided to go looking for interesting and more obscure facts and useful working information on trees. Where better to start than the mighty oak?

The words ‘hearts of oak’ stirs an impression of a tree that is strong and mighty and reliable, which indeed it is – but which oak are we talking about? Worldwide there are more than 270 species of oak excluding those we know of from pre-history!
Here are the two most common types that you can find in the UK:

English oak
English oak or pendunculate oak (Quercus robur). This sometimes produces local variants as tiger oak (when quartersawn) or brown oak due to growing conditions. The wide spreading ‘field oak’ with a level underside to the leaf canopy where it has been grazed, is the quintessential image of an English meadow landscape.

Sessile oak
Sessile oak (Quercus petraea), like the English oak, is home to lots of wildlife from plants to insects and birds. It differs in that the acorns are not carried on stalks (peduncles) but on the outer twigs (sessiles). It has a straighter trunk than the English oak. 

Did you know?
The sessile oak is the national native tree of Ireland. It is also common throughout Europe.  

Typical uses
Shipbuilding, timber framed houses, furniture, flooring, veneers and barrels for wine and spirits. Bark for medicinal anti-inflammatory use.

Timber conversion
English oak is typically sold as sawn waneyedge boards and can produce quite a bit of waste because of the growing behaviour of the trunk, with it’s thick rather deformed squat shape. Sessile oak is much straighter but still gives some waste. Nowadays it is unusual to have logs quartersawn because of economics and the method of resaw machining, which is only capable of ‘through’ cuts. This is a shame because oak on the quartering can show exceptionally fine ray-figuring. However, it can still be found in the top and bottommost slices in a log.

Did you know?
The oak was considered sacred by the thunder and lightning gods Zeus (Greek), Jupiter (Roman) and Dagda (Celtic) as the oak was often the tallest tree and thus easily struck by lightning.

History
Oak has been the wood of choice down the ages from medieval times onwards for shipbuilding, house framing and for tanning leather. Wealthy Tudor homes had oak panelled walls and furniture. Ships, especially for naval use, have been built of oak, the crooked nature of the branch structure being ideal for hull shapes. HMS Victory used about 6000 trees, mostly oak. Old ships timbers were often recycled as beams in timber framed houses. Oak bark was used for the process of tanning leather. Oaks were often cropped when relatively young as they were more manageable and could be coppiced like hazel. 

Choosing the timber
When you are trying to work out how much timber to buy for a project you may need up to 50% more than the job would suggest, due to removing the waneyedge and working around natural defects and splits. Oak boards ‘peak’ in the middle making it impossibly bowed and weak right in the centre of the heartwood, so a first longitudinal saw cut is inevitable, which affects how it can be used.

Working characteristics
• English oak is harder to work than more even, softer grained American white oak or Japanese oak.
• You can’t beat really sharp edge tools if you want a good trouble-free finish without too much effort.
• Always respect grain direction so you don’t tear angled grain.
• When routing burning can occur, so make a final lighter cut to remove the evidence.
• Chamfers are visually and touch-wise more pleasing than roundovers or complex profiles.
• Oak carves well, but not for fine detail because of the coarse grain structure. It doesn’t bend well, thus not suitable for curved lamination. • It is a dry non-greasy wood, the porous grain makes it a natural for glue jointing. A hand scraper will give a good result after planing.
• Oak only needs a sealer coat, such as hard wax oil and then paste wax unless you need a tough coat.
• Wirebrushing the grain and rubbing in liming wax creates a distinctive appearance.
• It can also be darkened through a process called ‘fuming’ using strong ammonia.
• Unfinished oak will stain badly if damp or wet due to the presence of tannin reacting with traces of iron. 

Food
Acorns from ‘white oaks’ (not the English oak) can be processed and turned into food. The tannins are removed by a process called leaching. This makes them safe and removes the bitterness. They are a source of vegetable protein and can be cooked like chestnuts or ground to turn them into flour for baking. 

Diseases
Like most native species the oak has its enemies – acute oak decline, chronic oak decline, the oak processionary moth and powdery mildew. 

Make your own discoveries
Why not visit your nearest arboretum, stately home or urban park and see which unusual trees you can identify? Let us know if you find something unusual, send a photo and details and we can publish it! Check out: The Tree Council www.treecouncil.org.uk.

Fascinating facts
• The Magna Carta and most documents until the 19th century were written on vellum, made from calf skin using a dense black ink derived from the oak gall which is itself created by the presence of the oak gall wasp. Strange to think a tiny wasp and a diseased lump on an oak tree can both record and make history.
•  29 May was once celebrated as Oak Apple Day in honour of King Charles II, who hid in an oak tree at Boscobel House to escape the Roundheads.
•  Oak trees only start producing acorns at forty years in age but can live for many hundreds of years.
•  Although rarely having the chance to be celebrated, an 80th wedding has oak as its symbol.