Q: I am new to this business and cannot get good answers about poplar lumber. I hear about yellow poplar in our N.C. operation and aspen poplar when I visit New England, but they are not the same wood to my eye. Can you take a moment to explain?

A:You have asked for clarification about an issue that can even confuse those people who are quite a bit more experienced. In brief, there is a genus called Populus . Within that genus are at least eight North American species that we see on the commercial lumber market, including trembling or quaking aspen or popple ( P. tremuloides ), bigtooth aspen or popple ( P. grandidentata ), balsam poplar, black poplar or balm of Gilead ( P. balsamifera ), Eastern cottonwood ( P. deltoids ), and black or California cottonwood ( P. trichocarpa ). (These species have other local names too; I have chosen the most common here.) In Europe and other continents, they also have species that are in the Populus genus.

It would not be uncommon to hear all of these, from time to time, except for Eastern cottonwood, called poplar, because they are in the Populus genus. However, the properties and color vary widely at times when comparing the various species. (Note that the genus name is always capitalized, and both species and genus are italicized, by convention.)

The National Hardwood Lumber Association calls quaking and bigtooth poplar by the name of aspen or popple in the grading rules. They do not use the name poplar at all for these two species. Incidentally, most aspen will be quaking, as bigtooth is not too plentiful.

Further, they use cottonwood for the cottonwood species.

This means that balm of Gilead is not clearly included in either grouping; in terms of processing, it would be closer to cottonwood however. In my experience, I have seen balm of Gilead lumber included with aspen (it is called balsam poplar then), but there is a big difference in color and drying properties, so this is probably not correct or desired.

Finally, the NHLA uses the term poplar for American tulipwood, which we know as yellow-poplar or tulip poplar in most cases. The Latin name for this tree is Liriodendron tulipifera . Its leaves are shaped like a tulip flower (if you use a small bit of imagination); hence the use of "tulip" in the species name. Note that it is not in the Populus genus. Nevertheless, within the trade, it is often called just poplar. Yellow-poplar is a much denser, stronger and stiffer wood than the species in the Populus genus. Oftentimes, yellow-poplar has a greenish hue to it, compared to the much whiter color of the Populus species woods.


Q: We make some products that have used treated wood in a few spots to eliminate the risk of decay. Now there is so much information in the newspapers about treated wood. Can you please make sense of all this for me...you write so clearly!

A:I am glad you find my writings helpful. Thanks for your support.

Regarding wood treated to eliminate the risk of decay and insects, I contacted the Southern Forest Products Association to make sure that I had the latest accurate information. There is a lot of fluff and politics involved for sure! Here is the story:

CCA lumber 1933 to 2001

For almost 70 years, Chromated Copper Arsenate (CCA) has served as the leading wood preservative in the United States and throughout the world. Its availability and widespread uses, including hundreds of applications ranging from decks/patios and wood-framed homes to saltwater marine structures, has made it the preferred choice for treated wood products. Since its introduction in 1933, CCA has experienced a sound reputation, but has also faced scrutiny by some environmental groups.

As treated wood gained popularity in the 1970s, the environmental focus was on perceived health dangers to workers in the preservative industry. In the 1980s, questions arose regarding the effects of CCA-treated wood on aquatic environments. A detailed, three-year study in the mid-1980s by the Environmental Protection Agency (EPA) determined that the benefits of CCA far outweighed any perceived risks. Additional studies, some industry-led, concurred. Results from the EPA study led to a voluntary industry campaign to distribute EPA-endorsed Consumer Information Sheets (CIS) that explained proper handling and use of treated wood.

As the 1990s unfolded, the focus changed again, this time to perceived issues surrounding CCA disposal.

By the turn of the century, concerns regarding arsenic exposure from CCA-treated playground equipment (perhaps related to improper disposal of sawdust from the construction project rather than leaching of chemicals is my opinion) were in the news. Although the alleged risks were scientifically unfounded, the spotlight never faded. During the past two years, an influx of negative publicity aimed at treated wood - its arsenic component and rumored health hazards - sparked creation of proposed state legislation to ban specific CCA-treated products in Florida, Louisiana, Massachusetts, Wisconsin, California and Minnesota. In several states, lawsuits seeking class action were filed. Pressure from environmental groups, concerned parents and politicians took its toll.

CCA in 2002

On Feb. 12, 2002, the leading wood preservative manufacturers entered into an agreement with the EPA to voluntarily withdraw the use of CCA from most consumer applications by the end of 2003.

Although most CCA-treated lumber products used in consumer applications have been voluntarily withdrawn in accordance with the EPA, the following industrial/commercial uses of CCA are still permitted: industrial, highway, and agricultural poles and pilings; saltwater marine exposures; selected engineered wood products (i.e., plywood, glued-laminated beams, structural composite lumber and shakes/shingles).

Replacing CCA-treated wood

The EPA does not believe there is any reason to remove or replace existing CCA-treated structures, including decks or playground equipment. The EPA is not recommending that existing structures or surrounding soil be removed or replaced.

There are two main replacement preservatives: ACQ (Alkaline Copper Quat) and copper azole.

ACQ-treated wood was first introduced in the United States10 years ago. It has been successfully used in Europe, Japan, New Zealand, Asia and Australia for the last 15 years. ACQ is a fixed preservative approved for full exposure to above ground, ground contact and freshwater applications.

Copper azole-treated wood has been used effectively around the world since 1992. Copper azole is a fixed preservative approved for full exposure to above ground, ground contact and freshwater applications.

Another alternative in some cases is borate. Wood products treated with borates were initially established in New Zealand in 1950. Before being introduced into the United States more than 10 years ago, borates were widely used in New Zealand, Europe and Southeast Asia. Borates are a diffusible preservative approved only for above-ground applications that are continuously protected from liquid water such as sill plates and other enclosed structural framing. In most cases, such "dry" uses in the United States would not require treated wood.


Q: I need to know what the difference is between black gum compared to sweet gum, and how do I identify black gum? I think I am getting black gum in my sweet gum and our customers do not want it.

A:Sweetgum (Latin name Liquidambar styraciflua ) has white to light pink sapwood (sometimes sold as sap gum) and reddish brown to brown heartwood (sometimes sold as red gum).

Black gum (sometimes called tupelo gum) (Latin name Nyssa sylvatica ) has sapwood that is light gray brown and heartwood that is darker gray brown.

Positive separation of the wood (if the color does not provide obvious separation) can only be done with a microscope. Even with 10 magnification, they cannot be separated with certainty. I am curious what keys your customers are using to indicate they have black gum, as the experts cannot usually separate the two! 

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