Current Step

• 1a – Opposite leaf arrangement on stem — go to 2

• 1b – Alternate leaf arrangement on stem — go to 18

• 1c – Sub-opposite leaf arrangement on stem. Some opposite and/or alternate leaves may also be present. Thorn at end of stem. Venation is arcuate (veins are arch-like extending from main vein, arching around the leaf margin, ending up near the leaf tip. — Common Buckthorn

• 1d – Leaves whorled (3 or more attached at the same node around the stem) — Northern Catalpa

Resources

• Identifying Broadleaf Flowering Trees and Shrubs, CMG GardenNotes #173
• List of trees in this key
• Glossary of Terms
• Front Range Tree Recommendation List
• Online CSU Extension publications on Tree and Shrub Selection

November 2017