Monday, January 24, 2011

Evergreen Valley Oak (Quercus lobata)

Quercus lobata is the signature oak of the Great Valley of California and adjacent areas. These trees are notable for they are amongst the largest in the genus (Jepson 1910). Quercus lobata is placed in Section Quercus (Nixon & Muller 1997) which includes both evergreen and deciduous members. Nixon (2002) considered Q. lobata most closely related to two other deciduous species: Q. garryana and Q. douglasii. However, there are evergreen members of Section Quercus: hybrids with Q. pacifica (which Nixon & Muller 1997 term "subevergreen", implying retention of some leaves year-round) are known.

Canopy retention into the very late fall or early winter in Q. lobata can be observed throughout its geographic range. Here I report a seedling that has essentially retained its leaves year-round for the past three winters.

This particular seedling originated from acorns gathered in John Muir's house in Martinez, California. This tree is growing essentially in a frost free coastal setting (Aptos, CA where frost over the past 3 yr has occurred only for 4 hours total). The essentially evergreen character of this seeding suggests a juvenile feature, which might be expected to change with maturity. The photograph is of the sapling (now about 6 feet tall) on Jan 24, 2011

Nixon, K.C. and C.H. Muller. 1997. Quercus Section Quercus. Flora North America, Vol. 3.

Nixon, K.C. 2002. The Oak (Quercus) Biodiversity of California and Adjacent Regions, pp. 3-20 in Standiford, Richard B.; McCreary, Douglas; Purcell, Kathryn L.; technical coordinators; Proceedings of the fifth symposium on oak woodlands: oaks in California's changing landscape. 2001 October 22-25; San Diego, CA. USDA Forest Service Gen. Tech. Rep. PSW-GTR-184.

Jepson, W.L. 1910. Silva of California. Memoirs University of California, Berkeley.

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