Martin O'Brien writes:

Typically, yew has extremely tight grain like maple while elm has open

grain similar to oak, but very wavy.  Ewe is pronounced the same as yew

(yoo) but means female sheep.  You should not see pores in yew, but

you would see them in elm.  I would agree that they are similar in density,

but I think that is where the similarity ends.

Yew is a conifer like pine and elm is like oak in that it looses its leaves

every year.  Yew as a tree lives hundreds if not close to a thousand

years.  I think it is the tree with the greatest longevity.  Even with this

longevity though, yew lumber does not typically yield very wide boards. 

Elm on the other hand does yield some generous widths.

Unless there is an extremely dark coating on yew and elm they should be

distinguishable from one another.

I've scanned some images of yew and elm for comparison.  They are not

very clear, but may help.  These are from The Woodbook published by Taschen.

MartinO
NC