X Sorbopyrus auricularis (Knoop) Schneider
AN UNUSUAL PEAR RELATIVE

Sorbopyrus is an intergeneric hybrid which originated sometime before 1610, probably in Europe, and has since been propagated as a clone. The name Sorbopyrus is derived from the two parents, mountain ash (Sorbus) and pear (Pyrus). In his Manual of Cultivated Trees and Shrubs, Alfred Rehder listed this plant as X Sorbopyrus auricularis (Knoop) Schneider. Plants that are a cross between two different genera begin with an "X". Hybrids between two different species of the same genus have a lower case "x" between the genus name and the species name. Hillier calls this plant the "Bolwyller Pear".

Sorbopyrus is a presumed hybrid between Pyrus communis L. and the simple leaved Sorbus aria (L.) Crantz., or European White Beam. It is not derived from a Mountain Ash with compound leaves like the Sorbus aucuparia L. commonly grown as a street tree. Sorbopyrus is represented in various arboreta and botanic gardens around the world, but has not been widely cultivated for it's fruit. Cuttings imported by the Arnold Arboretum around 1917 (PI 44048) were from a specimen "originally grown in Paris in 1834, where it formed a tree more than 30 feet high with a rounded bushy head." Scions were also introduced from the Paris Museum of Natural History in 1920 (PI 51702) to the US Plant Introduction Station in Glenn Dale, Maryland. A more recent introduction from Belgrade, Yugoslavia in 1959 (PI 260199) with the cultivar name 'Shipova' is identical to our Sorbopyrus tree.

Sorbopyrus is slow to begin bearing, but the tasty fruit is worth the wait. Fruits are turbinate, about 2 inches long and wide, and ripen in mid-August. They are about the size of a plum or large apricot, slightly pear shaped, and ripen to a deep yellow with an attractive orange-red blush when exposed to the sun. The lack of viable seeds, which appear as shriveled up seed coats, attest to its hybrid origin.

Like its Sorbus parent, Sorbopyrus is quite hardy. Rehder lists it as zone 5. It seems to be quite resistant to scab and other diseases. In years when unsprayed 'Bartlett' pears are completely covered with scab, Sorbopyrus has only a few scattered spots. It is apparently susceptible to fireblight, however.

Sorbopyrus has been renamed many times during the past 400 years. The plants introduced from Paris were labeled X Pyrus malifolia Spach. Taxonomists have reassigned this plant to a number of different genera and species inluding: "Pyrus malifolia", "Pyraria malifolia", "Sorbus bollwylleriana" and "Bollwilleria auricularis". A type reputed to be more pear-like, with fruit to 4 cm across is listed by Rehder as Sorbopyrus auricularis var. bulbiformis (Tatar) Schneider. Perhaps this is the type we are growing, as we have measured a few fruits over 6 cm across. We grow Sorbopyrus on pear rootstock, and are investigating the effect on pear cultivars when it is used as an interstock.

J. D. Postman, 12/95