Leaves are deciduous, opposite, pinnately compound, 6-12" long, with 5-7 lanceolate to narrowly ovate leaflets with serrated margins and noticeable unequal leaf bases. Leaflets are about 2-4" long and about 1" wide, and medium green. Trees growing with little water have smaller leaves that are often curled.
Flowers yellowish white, in a flat topped cyme. Individually small, but in large quantities making a nice display.
Fruit is blue when ripe, 3/8' diameter, sometimes with a distinct waxy covering. Infructescence gets very heavy and hang when fruit is ripe.
Young stems are bright green with orangish lenticels. Suckers can be very thick and grow very rapidly.
Bark on older trees is ridged, reddish brown in color.
I learned this plant as Sambucus caerulea back in the day, and will always recall seeing them all over Pullman WA and "getting" the caerulea part due to the fruit color. Also called S. mexicana caerulea or S. nigra cerulean.
Misidentification:
Not hard to identify, suckering habit, unequal leaflet bases, blue fruit.
Location:
Just about everywhere you find native plants growing.
Aptos
Nisene Marks all over the road prior to the pay station,
502 Loma Prieta Dr.