Arthur Temple College of Forestry and Agriculture

 

Quercus germana – Royal oak

Royal Oak
This cloud forest Mexico oak is rarely encountered in the USA.  It is native to East and N.E. Mexico, usually found at 800-1800 m. (2625-5905 ft.).  The species reaches 25 m. (82 ft.) tall, but should be smaller in cultivation.  We have two Royal oaks over ten years old and have been distributing acorns to interested nurserymen.


Leaves are lustrous, green, and glabrous, 9-13 cm. (3.5-5.1 in.) long and 3-5 cm. (1.2-2.0 in.) wide.  Leaves are persistent or semi-evergreen, oblong to oboval or oblanceolate.  Acorns are large and can be up to 4-5 cm. (1.6-2.0 in.) long and 2-3 cm. (.8-1.2 in.) wide, and single on a short peduncle. Prior to maturing, almost the entire nut is enclosed by a warty, pubescent cup.  Two trees in the SFA Gardens have experienced winter freeze events less than -12oC (10oF) with only minor foliage damage.  While wet mountainous forests describe the native habitat, the species appears quite heat and drought tolerant once well established. 

Acorns germinate readily for us, quickly forming a vigorous tap root, before sending up a shoot.  We have learned over the years that the young plants are very susceptible to overwatering.  They should be grown on the dry side.  We suspect the tree will be hardy in Zones 8 and 9, and deserve testing in colder zones as well. 

Acorns at time of falling from the tree are large and germinate quickly when planted.  It is best to harvest acorns while they are still attached to the trees; weevils attack acorns on the ground quickly.  We have also observed vivipary (germination while still attached to the tree) and we recommend that they be sown in the fall and the emerging seedling should be protected from freezing temperatures that first winter.

David Creech, Director of SFA Gardens

Royal Oak LeavesRoyal Oak AcornRoyal Oak Acorn in hand