1. What’s in that Woodpile? Firewood Identification
Firewood is a pathway for movement of invasive species. Knowing the species of wood a pest is found on or in can provide clues to identifying the pest.

2. Since so many problems are associated with the transport of firewood, firewood identification is becoming a more important monitoring tool.
How might we begin to identify the species of wood found in this firewood pile?

3. Wood Id: Key Characteristics
Cellular structures
Presence or absence of pitch
Bark
Color, pattern, thickness
Wood color
Density
Odor

4. Cell structure Hardwoods Softwoods Pores (Vessels) Ray cells
Ring vs Diffuse porous
Ray cells
Fibers, parenchyma & tracheid cells
Softwoods
Tracheids
Resin canals
Firewood will either fall into the softwood or the hardwood category. Neither category refers to the strength of the wood, rather it is based on whether the tree is a gymnosperm or angiosperm.
Hardwoods are more complex and thus easier to identify without magnification. Softwood anatomy is less complicated than hardwood anatomy thus there are fewer features to use for identification.
Hardwood vessels or pore size and arrangement are keys to identification. The presence or absence of ray cells can distinguish between oak and ash as well as other species. The fibers, parenchyma and tracheid cells create both texture and color in the hardwoods.
In softwoods tracheids are the most common type of cell and are responsible for the wood texture. Actually it is the cell diameter of the tracheid that produces the texture. Resin canals are not cells but spaces between specialized epithelial cells. These occur in four genera, pines, larch, spruce and douglas-fir

5. Ring Porous vs Diffuse Porous
Ring Porous wood has large pores in earlywood and small pores in latewood
Earlywood shows as obvious lines
Most firewood monitored for invasive pests is ring porous
Hardwoods are further classified as either ring porous or diffuse porous. Ring porous woods have distinct “layers” of wood within an annual growth ring. The spring or earlywood is comprised of larger vessels (pores), while the slower growing summer or late wood produces pores that are very small in diameter and tightly arranged. In the heartwood (the discolored center wood of some cross sections), the spring wood often looks lighter in color. In sapwood (the lighter, not discolored wood in cross sections), the spring wood often looks a bit darker. The point is, with a hand lens or strong eye sight, one can distinguish the layers of spring versus summer wood.
Most firewood that needs to be monitored for invasive pests is ring porous.

6. Ring Porous Wood: Black Ash
All ash are ring porous, such as this black ash.

7. Ring Porous Wood: Green Ash
All ashes are ring porous, such as this black ash.

8. Ring Porous Wood: Bur Oak
All oaks are ring porous.

9. Ring Porous Wood: American Elm
Elms are ring porous.

10. Diffuse Porous
Pores about same size and distributed evenly throughout growth ring = Diffuse Porous.
Diffuse porous woods do not have the distinct layers of spring and summer wood. The wood within an annual growth rings appears fairly homogenous.

11. Diffuse Porous Wood: Basswood
Basswood (Tilia, Linden) is a classic example of diffuse porous wood.

12. Diffuse Porous Wood: Boxelder
Boxelder and all other maples are diffuse porous.

13. Diffuse Porous Wood: Big Toothed Aspen
Most species of Populus including big-toothed aspen are diffuse porous.

14. Semi Ring Porous: Black Walnut
Semi-Ring-Porous Hardwoods
Pores: earlywood pores fairly large, decreasing
gradually to quite small in outer latewood; pores
solitary or in radial multiples of 2 to several
Rays: fine, visible but not conspicuous with hand
lens, 1-5 seriate, cells appear round in tangential
view

15. “Other” Features: Elm Bark Cross-Section
Layered Bark of American and Rock Elm
So, for most firewood monitoring instances, ring porous woods are the potential vectors. For example, oak wilt, Dutch elm disease, emerald ash borer. It’s not always so easy to distinguish between ring and diffuse porous pieces of firewood, but there are some other unique characteristics. For instance, the bark cross sections of rock and American elm have a two-colored, layered appearance. This is sometime referred to as “bacon strips,” or “oreo cookie” bark.

16. “Other” Features: Long-Grain of Elm
Another annoying characteristic of elm firewood is the stringy, long grain. Sometimes, this is referred to as “string cheese” long grain.

17. “Other” Features of Oak: Rays
Oak and ash cross sections can look very similar, but oaks have distinct parenchymal rays, whereas ash don’t.

18. Versus, No Rays in Ash Cracks or Checks, but not Rays
Sometimes when ash firewood cracks or checks, it may look like rays, but if examined closer it’s obvious that these lines are random cracks and not continuous rays.

19. “Other” Features: Elm and Hackberry
American Elm
Elms and hackberry also have kind of a unique characteristic to their summer wood. If you look at the wood in cross section, it has kind of a wavy “tiretrack” appearance to the summer wood. This is most noticeable with a hand lens.
Both Have Wavy (tire track) latewood

20. “Other” Features: Elm and Hackberry
Hackberry has Corky Ridges on Bark, no Layered Cross-Section
Elms and hackberry are often confused for each other, but hackberry does not have the “bacon strip” bark in cross section, and American elm does not have the characteristic corky or “warty” bark that hackberry has.

21. “Other” Features: Red vs. White Oak
Sodium Nitrite turns White Oak Heart Wood Blue to Purple
Finally, if it’s important to distinguish between white oaks (bur, white, bicolor) and red oaks (red, Eastern pin, Northern pin, black), a small amount of sodium nitrite applied to the heartwood reveals the true tree. White oak heartwood will turn a bluish/purplish color while red oak heartwood just looks wet and then dries to the original color.

22. “Other” Features: Black Walnut
Medium brown to dark chocolate heartwood.
Black Walnut
Medium brown to dark chocolate heartwood.
Semi-Ring-Porous Hardwoods
Pores: earlywood pores fairly large, decreasing
gradually to quite small in outer latewood; pores
solitary or in radial multiples of 2 to several
Rays: fine, visible but not conspicuous with hand
lens, 1-5 seriate, cells appear round in tangential
view

23. Let’s Quiz the Log Splitter!
This is strictly for fun and to wake people up. Feel free to skip it for the First Detector training. These are representatives of a state-wide survey conducted by the Department of Forest Resources, Outreach and Extension. The survey focussed on determining the 20, most-common species of firewood found in Minnesota.

24. Which log is hardwood?

25. Which log is hardwood? Log on the left Log on the right
Response Counter

26. What is this?

27. What is this? Oak Ash Walnut It’s hardwood; that’s all I need to know.
I don’t know.
Response Counter

28. What is this?

29. What is this?
Maple
Oak
Walnut
Pine
Don’t know.
Response Counter

30. What is It?
The furrows are often described as “canoe shaped” or “diamond shaped.”

31. What is it?
Linden
Sugar Maple
Black Ash
Elm
Green Ash
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32. Resource for Wood Id
Identifying Wood: Accurate Results with Simple Tools by R. Bruce Hoadley Tauton Press, 1990 Under $30

33. Gary Johnson
UM Urban & Community Forester
University of Minnesota Extension Foresters:
Angela Gupta, Rochester
Mike Reichenbach, Cloquet
Gary Wyatt, Mankato

34. Softwoods Softwoods have Tracheids (fibers) Resin canals Resin Canals
many softwoods have resin canals from which sticky resin exudes.
Pines, Douglas-fir, Spruce, Larch and Fir are all classified as softwoods based on these botanical characteristics, even though they’re very strong wooded trees.
In temperate zones, hardwoods are generally known for loosing their leaves in winter. Some common hardwoods include, maple, ash, aspen, cottonwood, willow, alder, birch, walnut, and basswood
Softwoods have
Tracheids (fibers)
Resin canals

35. Hardwoods Pores Hardwoods have Pores Fibers Ray cells Parenchyma
Hardwoods like softwoods also have tracheids, but also have vessel elements (pores) and lack resin canals. So, even though poplars, willows and boxelders are not considered fine and strong building woods, they are botanically classified as hardwoods.

36. A neatly stacked woodpile that looks pretty safe
A neatly stacked woodpile that looks pretty safe. But could it be harboring introduced or native invasive pests? Since so many problems are associated with the transport of firewood, firewood identification is becoming a more important monitoring tool.

37. What is It?
Characteristic copper colored, peeling outer bark with strong, horizontal lenticels.

38. What is it? Hackberry Chokecherry Crabapple River Birch Chokeberry
The bark may appear white, but it’s just a waxy “bloom” that can easily be rubbed off.
Response Counter 38

39. What is It?
Lightly green, photosynthetic bark with diamond shaped patterns to the development of older bark.

40. What is it? Birch Cottonwood Big-Toothed Aspen Silver Maple
Black Cherry
The bark may appear white, but it’s just a waxy “bloom” that can easily be rubbed off.
Response Counter

41. What is It?
Vibrant red and yellow colors of the heartwood and sapwood (respectively), as well as a pretty distinct “tire track” pattern to the summer wood.

42. What is it? Black Walnut Buckthorn Bur Oak Boxelder Ironwood
The bark may appear white, but it’s just a waxy “bloom” that can easily be rubbed off.
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43. What is It?
Deeply furrowed, ridged bark, easy to penetrate with a knife.

44. What Is It?
Cottonwood
Green Ash
Hackberry
Elm
Linden
Response Counter

45. What is It?
The bark strips off easily in long, vertical strips. If you could pick up a chunk of this as firewood, it weighs a lot.

46. What is it?
Elm
Boxelder
Silver Maple
Ironwood
Linden
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47. What is It?
When younger, this tree has reddish-brown, shiny bark with strong, horizontal lenticels. As it ages, the outer bark becomes darker and very “platey.”

48. What is it? Black Pine Black Cherry Austrian Pine Douglas Fir
White Cedar
The bark may appear white, but it’s just a waxy “bloom” that can easily be rubbed off.
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