With heavy rain on Thursday and more predicted for Friday our program and tour at the Arboretum appeared to be threatened. Our outside lunch was changed to the Inside Peacock Café but the rained on cleared on Friday morning to beautiful slightly cloudy weather. Richard Schulhof our member and Executive Director had organized a tram tour of the Arboretum’s Talac Knoll the San Gabriel Valley’s finest grove of Engelmann Oak, which is arguably the most outstanding natural heritage feature in Arcadia. The tour conducted by Jim Henrich the Living Collections Curator. Its his job to keep track of the 11,000 or so species at the Arboretum and know them by name (and the names sometimes change as plant species are studied over time. Jim started his program in the tram and then it continued as he invited us to stand among the Engelmann Oaks at Talac Knoll the highest pint in the Arboretum. It was created will the help of the Raymond Hill fault line that pushed the ground up.

The Engelmann Oak is native to the San Gabriel Valley and used to span from the Pacific Ocean in California to Arizona and then onto Mexico. Oaks are truly spectacular trees, but in our area the grandest is the rare Engelmann Oak (quercus engelmannii). Most oaks we see on the coastal plain of Southern California are the trademark Coast Live Oak (quercus agrifolia). It’s dark green leaves and dense foliage can be spotted everywhere. The Coast Live Oak is an impressive tree, but the majesty of the Engelmann can take your breath away. Their large twisted spreading limbs generally form a sparse crown. Their gray/green leaves are more elliptical or oval than the Coast Live Oaks, and their acorns more stubby. They often reside near Coast Live Oaks and Sycamores.

A separate species, Engelmann Oaks only exist in a narrow band that stretches along the foothills of Southern California from Pasadena through Arcadia and down through Orange and San Diego County into Baja California. They need to be twenty miles or more away from the ocean at an elevation of 500-4000 feet. In Southern California these spectacular trees have had a hard time because the mesas on which they are usually found are also ideal sites for homes. Engelmann Oaks are probably the most imperiled of all tree oaks and are one of the most endangered natural plant communities in California.

The tour ended with a view of the beautiful San Gabriel Mountains from the hill. Truly a spectacular day at the Arboretum to help celebrate the 139th Arbor Day.