Quercus robur L. subsp. microcarpa

Horticultural & Botanical History

Knight describes Quercus microcarpa as a variety of Quercus sessiliflora [English Cyclopaedia, Natural history vol.4, p.518/1856].  However its origin is uncertain and it may well be a hybrid, x Quercus ludoviciana var. microcarpa (Dippel) Rehder, the name published in Jour. Arnold Arb. 7: 239. 1926.  ‘Sargent’s description of this ambiguous hybrid and the notes on it by Rehder under the name accepted here were based on trees cultivated in the Arnold Arboretum and obtained from the nurseries of Wezelburg and Sons, Hazerswaoude, Holland, in 1903 under the name of Quercus chinensis microcarpa.  It appears to have been in cultivation in European gardens for many years under this name or as Q. microcarpa, Q. robur microcarpa, or Q. Phellos microcarpa.  The origin of the plant is unknown and its relationship seems to be very doubtful.  Quercus Phellos appears to be one of the parents, but there is little to suggest any known form of Q. falcata.  The leaves are mostly linear-lanceolate or oblong-lanceolate in outline, of approximately the size and relative length and breadth of those of the willow-oak, but nearly all of them are toothed or lobed on the margins with sharp or obscure bristle-tipped projections.  On some blades the lobes or teeth are symmetric and paired and on others they are very irregular.  The young branchlets and the under surface of the young leaves are covered with a pale, easily detachable pubescence, but they become quite glabrous late in the season.  The acorns are similar in shape to those of the willow-oak, but are smaller than the average for that tree.  It is possible that the plant may have arisen as a cross between Quercus incana and Q. Phellos.  But as the leaves in typical forms of both of these species are entire, it would not be expected that a hybrid between them would have toothed or lobed leaves.  It may also be noted that Quercus incana has not been successfully grown at the Arnold Arboretum, but the hybrid appears to be perfectly hardy, as is also the willow-oak.  While it seems to me to be quite unlikely that this supposed hybrid originated from a cross in which any form of Quercus falcata was involved, it is perhaps best in the absence of any positive evidence to leave it under its present name.  The trees in the Arboretum often produce good crops of acorns, and it is possible that if a series of seedlings was grown from them, some significant results might be obtained.’  [Journal of the Arnold Arboretum vol.XXIX, p.33/1948].

History at Camden Park

Listed in the 1845, 1850 and 1857 catalogues [T.805/1845].

Notes

Quercus microcarpa Small  = Quercus nigra var. heterophylla (Ait.) Ashe, a shrubby species from North America growing to about 5m tall.  [Britton – North American trees p.300/1908].  This is a possibility.  I have found no date of publication for Small.  This plant may be synonymous with Quercus microcarpa Michaux but again I have no data.