Identifying Firewood in British Deciduous Woods
The first time I went looking for firewood in some woodland that contained a variety of different species, I got quite confused! When looking for firewood you want dead wood, preferably a year or two old. This means leaves, buds and twigs which could have been used to identify the tree may long since have disappeared. Added to this one of the best firewoods, ash, has bark that can be smooth (when young), deeply ridged (when old) and pretty much anything in between depending on age, so that’s not always a good guide either.
This page is the result of a bit of digging around on the web for useful resources on identifying wood by looking at cross sections. I’ve focussed on some of the best types of firewood found in Britain, all hardwoods (broad leaved trees) found in deciduous woodland. It is by no means comprehensive, and I’m no expert. You have been warned!
Note: there are many other good types of firewood other than those mentioned; the ones below just happen to be the ones that are abundant in the woods accessible to me.
My Method
Saw a piece of the wood you’ve found at right angles to the trunk to get a cross section. Use a sharp knife to remove a thin slice from the sawn end to leave you a smooth surface (sawing leaves a rough, ridged surface that can make it hard to see what’s going on). Use a hand lens of some sort to have a better look – you can just about manage without, but a lens makes it much easier to see the smaller features.
Terminology:
- Rays: radial lines from core to bark running perpendicular to growth rings. Wood rays function to transport food and water horizontally across the diameter of a tree.
- Heartwood: wood in the middle, doesn’t carry nutrients, used for support
- Sapwood: wood between heartwood an bark, carries water and nutrients
- Earlywood and Latewood: growth in spring (fast) and later (slower) in summer, forming growth rings
- Pores: sometimes known as vessels, pores are seen in cross section of hard woods – they are the tubes that carry water in the tree.
There’s a good introduction to all of these terms with pictures in this document: Wood Identification for Hardwood and Softwood Species Native to Tennessee.
Cross Section Pictures
I found the cross section pictures that appear below on the Dutch site Trees and Wood. I believe they were taken Raimund Aichbauer of the Dutch Wood Collectors Society – please let me know if I have wrongly attributed them.
According to the Trees and Wood site, they reflect what you would see with a 10-12x magnification hand lens.
Beech
Beech Cross Section
Picture credit: Raimund Aichbauer (www.nehosoc.nl).
- Cross section shows large, irregularly spaced rays usually visible to the unaided eye; several finer rays (visible with a hand lens) in between
- Rays visible as redish / brown flecks visible in longditudinal sections, sometimes more than 1mm high and generally around 3mm (max 10mm) long . You can see the longditudinal section by looking at the sides of a log split down the middle with an axe (ready to put on the fire).
- Fairly small pores, hard / impossible to see with the naked eye. No noticable change in size of pores between earlywood and latewood.
- Heartwood similar in colour to sapwood, sometimes has reddish tinge
- Bark is smooth, even in very old trees
Could be confused with:
- Sycamore: Larger rays numerous, fairly regularly spaced and appear about the same size; large rays appear as crowded flecks on tangential surface (Beech rays do not appear crowded on tangential surface); on radial surfaces rays flecks are longer than in beech. Pores occur in radial multiples. Note that while sycamore is not as good as beech, it is still a reasonable firewood.
Oak
- Heartwood is a different colour to sapwood
- Pores easily visible to the eye, much larger in early wood (“ring porous”)
- Cross section shows prominent rays easily visible to the eye – you can’t miss them! There are much finer rays in between, only just visible with a hand lens.
Ash
- Rays very fine, hard / impossible to see with the naked eye. Can usually be seen with a hand lens
- Pores visible to the naked eye in early wood, much smaller in late wood (not visible to the naked eye – “ring porous”).
- Early wood pale, latewood darker, pores in latewood often appear as white spots when viewed without magnification due to vasicentric parenchyma. Parenchyma also sometimes eaily identifiable in latewood as bands following growth ring (confluent)
- Bark deeply ridged in mature trees, smooth in young trees. Distinctive diamond pattern in mature trees.
- wood pale yellow / white; heartwood similar in colour to sapwood
- Reasonably easy to saw, very easy to split (esp. when green)
Could be confused with:
- Elm – pores are in wavy bands. Heartwood basically brown to red to white or grey, with streaks. Sapwood colour distinct from heartwood colour
Hawthorne
- Pores hard / impossible to see with the naked eye. No noticable change in size of pores between earlywood and latewood (Diffuse to semi-ring-porous). Pores generally occur singly (not in multiples as in birch).
- Fine rays (similar to Ash, slightly wider) fairly equally spaced; Up to 0.5mm in height when viewed in longditudinal (radial) sections (generally two to three cells wide).
Birch
Birch Cross Section
Picture credit: Raimund Aichbauer (www.nehosoc.nl).
Birch is a good firewood, although burns fast, so is best used with other slower burning varieties. It should be easily distinguished from Ash as it is diffuse porous rather than ring porous.
- Pores and rays numerous but do not appear crowded.
- Pores do not change in size noticably from earlywood to late wood (“diffuse porous”).
- Pores in multiples, commonly short (2–3 pores) radial rows (occasionally also in radial chains of 4–6)
- Rays usually indistinct except with a hand lens; widest rays still much narrower than the widest of the width of the largest pores; pores appearing as white dots to the naked eye.
It could potentially be confused with Lime (“Basswood” in the US). To distinguish the two:
- Lime – soft, low density; marginal parenchyma at growth rings (spotty); faint musty odour
- Birch – quite hard, dense; growth rings not distinct; rays barely visible to the naked eye; pores solitary or in multiples
Resources:
- Commercial timbers | Hamburg University Mirror an online database of commercially used timbers from around the world; comprehensive descriptions with links to pictures of various sections (sections appear to be thin slices photographed under a microscope – not as useful as the pictures from the Dutch Tree Directory when comparing to what you see with a hand lens)
- Wood Identification Study Guide for Forest Technology Students. Developed by Jeff Dubis (jdubis@maine.edu ) from the University of Maine at Fort Kent. Characteristics for identifying thirty common species. Great close up colour pictures of cross sections, showing longditudinal sections where they are useful in distinguishing between species.
- Trees and Wood is a Dutch Tree Directory, and has fantastic cross section pictures that reflect what you would see with a 10-12x magnification hand lens. Also has pictures of tree trunks and leaves.
- Wood Identification for Hardwood and Softwood Species Native to Tennessee (downloaded from the University of Tenesse’s Publications — Forestry, Trees & Timber) – descirbes how to identify several species common to Tenessee using a hand magnifying lens. Includes lots of details on the macro cross-section characteristics of wood, info on preparing the surface for examination and two nice keys for hard woods and soft woods.
- Microscopic Wood Anatomy has a very comprehensive list of species and lots of high res images of various sections – some of the features are unlikely to be visible with a hand lens though.
- Inside Wood another searchable database of hard wood species, with interactive key and lots of images
- How to Identify Some Common Indiana Woods includes good photos of cross sections (black and white) and some info on the macro cross-section characteristics of wood, and a key.
- Structure of Wood by the Society of Wood Science and Technology is a good introductory document covering the structure of wood and contains some good cross sectional pictures of various hardwoods and softwoods showing the detail you would see with a hand lens. Also available in slide form along with other teaching aids here.
- Identifying Ash Trees: Michagan State University has published a couple of useful documents with info on branching, buds, leaves etc. (note that these refer to US varieties of Ash, although many features are common with the European variety):
- Twigs and Buds:
- Trees in Winter. Nice pics and descriptions of twigs and buds of trees in winter.
- Twigs and Buds ID sheet this PDF from the woodland trust nature detectives site has more species than the bbc version.
- Sussex Hedgerow Woody Species Identification Guide – a useful general guide to leaves, fruit, bark / trunk and flowers of common hedgerow trees and shrubs found in Britain.
Hand Lenses
Here are a couple of websites I’ve found that supply hand lenses in the UK:
The Russian optical company Belomo make a 10x Triplet Loupe which seems to be well regarded. I purchased one from Rockhound (an Ebay seller in the US) – so far I’ve been very happy with it. Delivery to the UK via USPS First Class Mail International took a couple of weeks.
Books
Author of this page: Colin Brown, Jan 2008.
