Douglas fir and poplar are two beloved timbers. They can both provide so much to a project, whilst also being affordable, readily available, and sustainable. However, understanding which one is the best choice for your project requires more detailed knowledge about each tree’s unique properties.
In this article, we’ll discuss the differences and similarities between the two timbers so you can decide which one is best for your next woodworking project.
What Is Poplar?
In the US, poplar is perhaps the most widely used timber. This tree can be found everywhere, from pallets to construction and furniture.
Poplar grows throughout the eastern United States, where there are a few variations on its name, including yellow poplar and tulip. In this article, when this wood is mentioned, it refers directly to the yellow poplar, not the white poplar. Fully grown trees are capable of reaching heights of 160’ and the trunk can become 8’ thick.
Interestingly, poplar doesn’t belong to the ‘Populus’ scientific genus. In fact, the poplar tree is from the ‘Liriodendron’ genus, known as the ‘lily tree’ family. When trees from this genus flower, they look similar to lilies, which is how the tree also got the name ‘tulip wood’. The scientific name for poplar is Liriodendron tulipfera.
What Is Douglas Fir?
Douglas fir is a favorite timber for a lot of woodworkers, who often refer to it as ‘Dougie’. The tree has an exceptionally good strength-to-weight ratio and is relatively affordable. Douglas Fir takes its name from David Douglas, a Scottish botanist. Despite its name, this is not a true fir tree, as it is within a unique genus called Pseudotsuga.
These trees can grow very tall, up to 250,’ and their trunks can reach 6’ in diameter. Because of their size, a lot of timber can come from one tree, making this wood very commercially valuable.
Poplar vs. Douglas Fir: What Are the Differences?
Poplar and Douglas fir are very different types of wood. Understanding in detail what sets the trees apart from one another is key to learning which one suits your project’s needs.
Strength
The strength of timber depends on a lot of variables. To compare these two, we’ll look at the Janka hardness and crushing strength. However, make sure to inspect stock in person for defects because these will greatly reduce the strength of a board.
Poplar’s Janka hardness is 540 lbf and it has a crushing strength of 5,540 lbf/in2. Comparatively, Douglas fir has a Janka hardness of 620 lbf and a crushing strength of 6,950 lbf/in2.
The numbers show us that Douglas fir is generally stronger than poplar. Alongside this, because the tree grows to a larger size, timber of larger dimensions can be made from this tree, making it stronger. In a separate article, we wrote more about Douglas fir’s strength.
Color and Appearance
The heartwood of poplar can be anywhere between light cream and yellow-brown. It’s not uncommon for green and gray streaks to also be present in boards. The sapwood is similar to the heartwood and it’s often difficult to differentiate between the two.
Sometimes poplar is called ‘rainbow poplar’ – a rarer phenomenon where there’s a range of colors, including purple, red, green, and yellow, contained in a board.
The age and area that the tree grew in can change the appearance and color of Douglas fir. Often the wood is a light tone, with a slight yellow tint. The growth rings contrast each other, with the winter growth much darker than spring and summer. Douglas fir’s appearance can lend itself to beautiful, minimal, and modern designs. This is enhanced if it’s finished with a lightening agent.
Grain
Poplar is generally a straight and uniform-grained wood. Although depending on how a tree grows, this grain will not always be consistent.
The grain of Douglas fir will change depending on how the tree has been milled. Tangentially cut boards can show very unique grain patterns, whereas quartersawn are usually straight and uniform.
Workability
Poplar is one of the best and easiest timbers to work with. However, the softness of this wood does create difficulties when working with it. For example, poplar bruises quickly under compression. Alongside this, edges will crumble if not cut cleanly and decisively. Poplar is not a common cause of allergic reactions, although sometimes the dust and particles can cause irritation to the respiratory system, eyes, and skin.
Douglas fir will work nicely. Attention should be paid to the variation between winter and summer growth rings that can cause blades to catch and lift grain if a worker gets complacent. This wood generally stains, glues, and finishes well. Some woodworkers have reported skin irritation and nausea from working with douglas fir. However, these reactions are not common.
Sustainability
Both Douglas fir and poplar are not on the CITES Appendices or the IUCN Red List. Neither tree is of immediate concern and both are considered okay to use if sourced ethically and sustainably.
When to Use Poplar Wood?
Unless it is rainbow poplar, this timber is not often used in applications where it will be visible. Poplar fulfills a lot of functions and can be used for pallets, frames, plywood, crates, and upholstered furniture. Alongside this, the veneer is popular when dyed or as a balancing sheet for the underside of a board veneered with a more expensive timber on the visible face.
When to Use Douglas Fir?
One of the areas that Douglas fir excels in is timber framing. The timber’s strength-to-weight ratio lends itself perfectly to traditional framing techniques, where it can be a cheaper alternative to oak. Beyond this, the wood is great general construction lumber, but can also look beautiful in cabinetry and furniture.
Alternatives to Poplar and Douglas Fir
Poplar and Douglas fir are two timbers that are generally well stocked, and they should be fairly straightforward to source. However, sometimes it can be difficult to get even the most common building supplies. In these situations, consider looking at the alternative timbers below.
Ash
Ash is a strong timber that takes impacts well. Alongside this, the lighter tone of the wood can provide a modern aesthetic to a project. When there are large outbreaks of ash dieback disease, ash can sometimes be sourced cheaply.
Spruce
Spruce is a type of evergreen softwood. The wood is usually straight-grained and used in heavy construction work.
Summary
Poplar and Douglas fir are two common timbers that are vital to the woodworking industry. Used extensively for construction and general woodwork, if you are in the US, you are most likely close to either right now. If the wood is visible, generally, people favor Douglas fir over poplar. However, if you need lighter timber, then poplar is the better choice.