Columnar English Oak
Same shrub as observed one week earlier (the “no dog” sign in the background of the last photo was captured in both observations): https://www.inaturalist.org/observations/207304203
One week later, more (most) flowers have reached anthesis, but there are still some that have not matured.
Anther length estimated as: 1.1-1.2 mm (4th photo); 1.0 mm (5th photo).
Two flowers were removed from a catkin and photographed through the lens of a dissecting scope (second last photo). Elongated green nectar glands are visible protruding from the base of the flower.
Additional notes: Photos 2 and 4 were taken with a Canon Powershot camera and the remainder were taken with a cell phone. Photos 7 and 8 were taken through the lens of a dissecting scope.