I have been thinking about trying to make a self bow and I have been lucky enough to find some yew trees in an area that I am working. How big does a tree need to be to make a bow or stave?
Thanks
Jon

As little as 4" will work.  In fact smaller is fine but you will have a bit more crown to your back.  I've made bows from elm and hickory saplings as small as 3".  If I had my choice, I'd go with 10-14".

I like 8-10" for ideal, but down to 3 or 4 inches will work as John said. With yew, the search will be for clear sections with straight grain - no spiral twist which shows even in the bark. Yew tends to have lots of small limbs and lots of small knots associated with them. If you find a 6' clear 10" logs it will be very rare. Look for 36-40" prime sections that could be split and spliced at the handle as sister billets. Glenn St Charles' book and video called "Billets to Bows" are excellent aids for working with yew from harvest to finsihed bow.

PS, if you find some good yew and want to trade some of it for prime osage send me a PM.