What’s in Your Woodpile? Gary Johnson Urban and Community Forester University of Minnesota

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.

Approved Firewood Required on State- Owned Land Obtained from firewood distribution facility on State-owned land Obtained from a firewood dealer approved by the DNR commissioner DNR commissioner approved firewood. The rules as according to the Department of Natural Resources. The following is from the MN DNR website: http://www.dnr.state.mn.us/firewood/index.html Don't move firewood —Buy it where you burn it! • It is against the law (M.S. 89.551 Sec. 2 Subd.3b) to bring unapproved firewood into any state park, state forest or day-use area. • Find an approved firewood vendor near your destination, Be sure to keep your receipt to show proof of purchase. • Firewood can harbor many different kinds of invasive pests that are harmful to Minnesota trees. Firewood restrictions are needed to help prevent the introduction or spread of damaging forest pests including emerald ash borer, gypsy moth, and oak wilt. • Trees: Good; Bugs: Bad presentation about firewood restrictions and Emerald Ash Borer. (you will need a Adobe Flash Player to view presentation) http://files.dnr.state.mn.us/assistance/backyard/treecare/forest_health/treesGoodBugsBad/Presentation_Files/index.html (a) After the commissioner issues an order under paragraph (b), a person may not possess firewood on land administered by the commissioner of natural resources unless the firewood: (1) was obtained from a firewood distribution facility located on land administered by the commissioner; (2) was obtained from a firewood dealer who is selling firewood that is approved by the commissioner under paragraph (b); or (3) has been approved by the commissioner of natural resources under paragraph (b). (b) The commissioner of natural resources shall, by written order published in the State Register, approve firewood for possession on lands administered by the commissioner. The order is not subject to the rulemaking provisions of chapter 14 and section 14.386 does not apply. (c) A violation under this section is subject to confiscation of firewood and after May 1, 2008, confiscation and a $100 penalty. A firewood dealer shall be subject to confiscation and assessed a $100 penalty for each sale of firewood not approved under the provisions of this section and sold for use on land administered by the commissioner. (d) For the purposes of this section, "firewood" means any wood that is intended for use in a campfire, as defined in section 88.01, subdivision 25. 2007 c 36 s 2

A pile of firewood like this is much more difficult to monitor unless it’s being distributed from an approved distribution facility.

Penalties: After May 1, 2008 Confiscation of firewood, and $100 penalty (purchaser), or $100 penalty for each sale (dealer) *Firewood: any wood intended for campfire. Self explanatory. Feel free to delete the reference to the Gopher football games! Deleted the following: or, Must purchase and attend full season of Gopher football games.

Softwood versus Hardwood Resin Canals To begin, firewood will either fall into the softwood or the hardwood category, neither of which infers strength of the wood. It’s a botanical classification system, and only means that softwoods lack the vessel elements (also called pores) that hardwoods have. In addition, 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. Softwoods have Tracheids (fibers), No Vessels (pores). Many have Resin Canals.

Softwoods versus Hardwoods Pores Hardwoods have Fibers and Pores 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.

Ring Porous versus Diffuse Porous Large Pores in Earlywood and Small Pores in Latewood = Ring Porous Hardwood Large, obvious lines are Earlywood. Smaller,darker heartwood or lighter sapwood lines are Latewood. 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.

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

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

Ring Porous Wood: American Elm Elms are ring porous.

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

Ring Porous versus 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.

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

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

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

“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.

“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.

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

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.

“Other” Features: Elm and Hackberry Both Have Wavy (tiretrack) summerwood 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.

“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.

“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.

“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

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.

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

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. 27

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

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.

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.

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. 31

What is It? Corky ridges on young trees, young branches.

What is it? White Oak Hickory Hackberry Winged Euonymus Bur Oak The bark may appear white, but it’s just a waxy “bloom” that can easily be rubbed off. 33

What is It? Deeply furrowed, ridged bark, easy to penetrate with a knife.

What Is It? Cottonwood Green Ash Hackberry Elm Linden

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.

What is it? Elm Boxelder Silver Maple Ironwood Linden

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.”

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. 39

What is It? Very light, thin vertical strips of bark peel off easily.

What is it? White Cedar Sugar Maple Ponderosa Pine Black Cherry Douglass Fir The bark may appear white, but it’s just a waxy “bloom” that can easily be rubbed off. 41

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

What is it? Linden Sugar Maple Black Ash Elm Green Ash

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