Elm Wood: Hard and Soft

by Eric Meier

The most basic division of elm species is between hard and soft elm. The wood of the hard elms (sometimes referred to as rock elm) generally range from 41 to 47 lbs/ft3, while soft elms typically have a density from 35 to 38 lbs/ft3.

Hard Elms:

Soft Elms:

Anatomical Identification

The primary element for distinguishing elm types is found in the earlywood pores. For elms in North America, hard elms are characterized by smaller earlywood pores that are closer in size to the latewood pores. The earlywood is generally in a single, broken row.

Cedar Elm (endgrain 10x)
Cedar Elm (endgrain 10x), a hard elm
Red Elm (endgrain 10x)
Red Elm (endgrain 10x), a soft elm

By contrast, soft elms tend to have larger earlywood pores. The earlywood may be one or two rows wide, as in American Elm (Ulmus americana), or two to four pores wide, as in Red Elm (U. rubra).

However, elm species from Europe and Asia do not always follow the same earlywood patterns as the North American species. Most notably, English Elm (U. procera) and Wych Elm (U. glabra) both have single, intermittent rows of smaller earlywood pores, but are considered soft elms.

Wych Elm (endgrain 10x)
Wych Elm (endgrain 10x), a soft elm with the anatomy of a North American hard elm

With the exception of the multiple earlywood rows found in Red Elm, individual species of both hard and soft elms cannot be further separated down to a species level.

Dutch Elm Disease

This fungal disease is spread by elm bark beetles, and has been responsible for the demise of tens of millions of elm trees in North America and Europe. As a result, disease-resistant cultivars and hybrids have been sought out. Hybrid elm trees may have characteristics from either of the parent trees, confounding identification.

Lookalikes

Elm is sometimes confused with ash (Fraxinus spp.), though the two can be separated based on elm’s wavy latewood bands.

White Ash (endgrain 10x)
White Ash (endgrain 10x), may exhibit mild ulmiform patterning, but it’s not as consistent through the entire latewood section as it is with elm

This zig-zag pattern, also called ulmiform, is even visible on flatsawn surfaces as minute jagged lines.

Red Elm (sealed)
Red Elm, ulmiform patterning is evident even on the face grain of elm as thin zig-zags between growth rings

Hackberry (Celtis occidentalis) is anatomically very similar to elm, though its wide sapwood and grey or yellowish color usually serve to differentiate it from elm.

Hackberry (sealed)
Hackberry frequently has a somewhat “dirty” and mottled appearance

Get the hard copy

wood-book-standupIf you’re interested in getting all that makes The Wood Database unique distilled into a single, real-world resource, there’s the book that’s based on the website—the Amazon.com best-seller, WOOD! Identifying and Using Hundreds of Woods Worldwide. It contains many of the most popular articles found on this website, as well as hundreds of wood profiles—laid out with the same clarity and convenience of the website—packaged in a shop-friendly hardcover book.

8
Share your experience

avatar
Photo and Image Files
 
 
 
6 Comment threads
2 Thread replies
0 Followers
 
Most reacted comment
Hottest comment thread
7 Comment authors
Danny O'FarrellRon GoeddeDan O'FarrellBryan SpoffordJ. Michael Cardell Recent comment authors
  Subscribe  
Notify of
Dan O'Farrell
Dan O'Farrell

Any articles that I’ve read about elm state that the wood is easily subject to rapid decay, if left exposed. Nevertheless, elm was the wood of preference for structural components of 17th and early 18th century ships made in Britain. Of particular note was the choice of elm for ships’ keels. Can someone please clarify this for me?

Ron Goedde
Ron Goedde

I have worked with both Red Elm and American Elm. American Elm decays quickly and is challenging to split. Red Elm on the other hand decays much slower and splits easily. The two versions of Elm have extremely different characteristics in decay and interlocking grain.

Danny O'Farrell
Danny O'Farrell

Thanks for the input, Ron. I imagine then that the English Elm is more likely of a “RED” variety. Further research has also indicated that large Elm posts were often the choice for bridge piles ( in England), apparently for the same reason.

Bryan Spofford
Bryan Spofford

Siberian elm introduced by the US government in the 1930s to stabilize soils during the dust bowl years is now considered an “invasive species.” Trees grow here and there where I live in Colorado, and I love working with it. In spite of an interlocked grain, it seems to work well and has beautiful appearance in a variety of smaller items. It seems to be very hard and has a smooth sanded feel like hard maple. A spalted log sitting in a gully for a couple of decades suggests that it is fairly rot resistant, and a large serving spoon… Read more »

J. Michael Cardell
J. Michael Cardell

Where I live in southeast Idaho, most of the elm is Siberian Elm (Ulmus pulmila). Echoing Anthony a few comments above, I would love to have some info on this species of Elm.

Anthony Langlois
Anthony Langlois

Ulmus pumila – Siberian Elm should be added to the database since it is rather common here in the States. Siberian Elm is often mistaken with Ulmus parvifolia – Chinese Elm even though they look completely different.

Charles Burns
Charles Burns

I would like to know how to tell the difference in trees by grain bark and leaves

Igor' Olechnowicz
Igor' Olechnowicz

Just to add to bunch of anecdotes here. Last year I purchased blindly n-th-hand (I suspect ‘n’ is more than 2) pieces of veneer. It claimed to be oak, but after I received my parcel, it turns definitely not. First I thought it was ash, often mistaken with oak, but after having read here Eric’s article about elms mentioning ulmiform, it appeared that pieces were elm – I used exact those portions of veneer with many of that spectacular ziggzagged patterns! Of course, I almost suspected it earlier, given its colour (astonishingly alike my local elm wood samples), but thought… Read more »