TREE OF MERIT
Skymaster English Oak (Quercus robur 'Skymaster')
English Oak leaves and fruits • Photo by Robert Vidéki,
Doroniucm Kft., Bugwood.org
Quercus robur 'Skymaster' is a phenomenal tree.
Skymaster English oak has a strong central leader and
upward sweeping branches, giving it an oval shape
that is more amenable to street use. Don't mistake
Skymaster for Skyrocket English oak. Skyrocket is a narrower cultivar with multiple leaders that can break under
snow loads, something Skymaster is not prone to.
Another claim to fame is Skymaster's resistance to
powdery mildew. Susceptibility to powdery mildew is
almost an ID feature on most English oaks. I have seen
the straight species understock English oak grow out
and look white with powdery mildew while the scion,
Skymaster, was clean and green.
English oak is hardy to Zone 5b, maybe 5a. Skymaster
grows moderately fast once it gets over transplanting
stress. On a good site it can grow to 50 feet (15 m) with
a 25 foot (8 m) spread, although it is less likely to reach
these dimensions on a street location.
Like other English oaks, Skymaster doesn't like poor
drainage, but it is quite drought tolerant once established. It is tolerant of alkaline or acid soils and should
be transplanted B&B. It is in the middle among the oaks
for transplanting ease, with swamp white oak (Quercus
bicolor) being easy and bur oak (Quercus macrocarpa)
and white oak (Quercus alba) being difficult.
'Skymaster' English Oak on Ithaca City streets • Photo by
Nina Bassuk
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—Nina Bassuk, Director of Urban Horticulture Institute,
Cornell University
City Trees