Using Leaf Scars to Distinguish Fraxinus in Central Texas
by Bob Harms  email-here

In the hope that leaf scars might be useful in distinguishing our 3 Central Texas taxa I encountered two difficulties: (1) old leaf scars were commonly compressed owing to growth of the stem; and (2) leaves prior to detaching naturally often tore, distorting the scar area. Consequently I decided to wait until mid November when leaves were either falling naturally or detached easily without distorting the scar. On November 15 & 19 I collected short branch sections from trees that I had been able to identify from samaras. In all I collected branches with scars and took images of over 130 scars. From these I selected the most representative scar images. Then for each taxon I selected 9 scars: 3 most typical scars, 3 that were similar to the typical but somewhat different in shape, and 3 that I felt would not be useful in distinguishing the taxa. These are presented in the table below, 3 columns, each with 3 images. [Note: The table is quite wide, so some horizontal scrolling may be needed.]

In my opinion no description will accommodate the full range of variation for a given taxon. But it does remain a useful differentia only if a large enough sampling is made, and a fresh bud is considered. The color of the bud with F. albicans is reddish brown. The bud of F. berlandieriana typically cuts a sharper notch into the top of the scar. The angle of the bud should be taken into consideration: upward with F. albicans and F. berlanderiana, outward with F. pennsylvanica.

Most typical Similar Difficult
F. albicans
FRAL3-scar-6-1xFRAL3-scar-6c-1xFRAL3-scar-10c-1x FRAL3-scar-7d-1xFRAL3-scar-7g-1xFRAL3-scar-12f-1x FRAL3-scar-3e-1xFRAL3-scar-9-1xFRAL3-scar-14d-1x
F. pennsylvanica
FRPE-BCk-scar-10e-1xFRPE-BCk-scar-2e-1xFRPE-BCk-oldscar-2b-1x FRPE-BCk-scar-1h-1xFRPE-BCk-scar-12-1xFRPE-BCk-scar-13-1x FRPE-BCk-scar-4-1xFRPE-BCk-scar-5f-1xFRPE-BCk-scar-7c-1x
F. berlandieriana
FRBE-BCk-scar-1e-1xFRBE-BCk-scar-4c-1xFRBE-BCk-scar-4h-1x FRBE-BCk-scar-5-1xFRBE-BCk-scar-6old-g-1xFRBE-BCk-scar-8b-1x FRBE-BCk-scar-1d-1xFRBE-BCk-scar-2c-1xFRBE-BCk-scar-4i-1x

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