Pinus nigra ''Hornibrookiana'
After Murray Hornibrook, an authority on dwarf pines.
A dwarf evergreen conifer with short, stiff, glossy green needles. Very dense with an irregular globose form. Discovered as a witch's broom in Seneca Park, Rochester, New York. Prefers full sun in well-drained soil. 2' tall x 2' wide in 10 years. Hardy to -30 degrees.
Here is a link that might be useful: More info on 'Hornibrookiana'