Some of the more hardy varieties as reported by Slate (1930) include the following: (a) White Lambert (not of value) (_C. maxima_); (b) Red Lambert (_C. maxima_); (c) Cosford; (d) Purple Aveline (_C. avellana_); and (e) Early Globe (of little value).
Some of the varieties upon which both the staminate and pistillate flowers tend to bloom relatively late are (a) Althaldensleber, (b) Kentish Cob, (c) Red Aveline, (d) Purple Aveline, and (e) Bolwiller. Late blooming, however, does not necessarily insure escaping injury from low spring temperatures. The Cosford, Italian Red, and Medium Long are considered by Slate as good for New York. The Bixby and Buchanan are the result of crossing _C. americana_ x _C. avellana_, and appear to be of promise for home plantings in the East. Mr. H. F. Stoke is growing the Italian Red and Du Chilly (Kentish Cob) with Daviana for pollination purposes in the Roanoke area.
CROSS-POLLINATION. A fourth limitation is the fact that varieties are nearly entirely if not fully dependent upon cross-pollinization by other inter-fertile varieties that bloom at about the same time in order to insure a set of nuts. This limitation may be overcome by the proper planning of hardy varieties are inter-fertile. Colby (1944) has reported that the Winkler variety is self-fertile.
SUCKERS. A sixth limitation is the tendency of the _C. avellana_ or _C. maxima_ to sprout about the base and the labor and expense of keeping these sprouts pruned out. It is possible that this factor may be overcome by using Turkish hazel (_C. colurna_ L.) as an understock and grafting or budding thereon the varieties that sprout when on their own roots. The Turkish hazel does not sprout as badly as the two other species.
Note by Editor: An Oregon nursery, which formerly propagated European filberts on the Turkish understock, now has abandoned its use. The grafted filbert tops did not seem to survive and bear as consistently as those on their own roots, after a period of several years in orchards.
PLANTING IN VIRGINIA. In a letter dated May 17, 1948, addressed to R. C. Moore, Assistant Horticulturist, V.P.I., H. J. Pettit, Assistant Secretary of the Planters Peanut Company, Suffolk, Virginia, reported that some years ago they planted several thousand trees of filberts, which they obtained from the states of New York and Oregon. From their experience it appears that late spring frosts destroyed the flower parts, which developed early, with the result that the yields were too low to be profitable. Hence, the filberts were removed and the land otherwise utilized. Mr. H. F. Stoke, however, in the Roanoke area has not found lack of hardiness as serious as the problems of diseases and insects of filberts.