This beautiful evergreen Asian oak tends to form multiple trunks bearing a dense crown of glossy green leaves with chalky blue undersides.
Peckerwood is known for its extensive oak collection, especially those from John’s Mexican collections, but we do have a variety of Asian oaks as well. A few decades ago, John imported seeds of Quercus glauca, also known as the Japanese Blue Oak or Ring-Cupped Oak. They germinated well and were offered through Yucca-do Nursery locally and via mail order, but according to John none sold, presumably due to being just too unfamiliar to collectors at that time. After sitting around for a while, they were eventually planted around the Peckerwood and Yucca-do properties. As they attained significant size, people finally began to notice what attractive evergreen trees they had become, with spreading branching structure, multiple trunks and smooth polychrome bark in shades of silver, white, light green and grey. Many did not immediately recognized these trees as oaks, being the thick, stiff glossy leaves with dark green tops and chalky blue undersides didn’t look remotely like any familiar North American oak. The spreading branching structure was especially appealing, combined with the naturally dense crown. These trees began producing seed –recognizable as a standard oak acorn, but with concentric rings encircling the cap, hence one of the common names (Ring-Cupped Oak). With mature trees to behold in the garden, and now offspring, there were now customers lined up for the opportunity to finally grow this tree that had to earn its admiration over time in the Peckerwood landscape.
I have been fortunate to see Q. glauca in Taiwan where it is native. It occurs in low elevation tropical forests that are rather dry, yet when grown in colder areas it is quite tolerant of hard freezes it would not otherwise see naturally. It does get some damage in zone 7 but excels in zone 8 to 10. It seems adaptable to any location with well-drained soil and full sun to light shade. I think the best specimens are attained in full exposure, starting out as a compact tree with a fairly upright habit, and eventually producing additional trunks that spread gracefully outward. If grown in shadier conditions, it will grow more vertical, less spreading, as it reaches for the light. Examples of both forms growing in these different conditions can be observed at Peckerwood, and both have their merits.
In March, the new growth emerges a purple-bronze color that is quite attractive, and when the tree is a little older this growth will be accompanied by hanging catkins of flowers. Of particular note are the trees on the west side of the nursery property, as they did not receive any supplemental water in the most recent prolonged drought, yet they really never missed a beat. Taiwan was in a severe drought when I visited in early 2015, and many adjacent natives were clearly wilted and suffering while Q. glauca looked flawless.
— Adam Black