By Bob Purvis
Over the past 10 years, a number of early-ripening apple varieties have become available to Alaskan fruit growers. Only a little work has been done, however, on finding European plum (Prunus domestics) cultivars suitable for Alaska, but there are some good reasons for considering them for home orchards south of the Alaska Range.
As a species of Prunus European plums are less hardy (zones 8-4) than the American hybrid plums, but hardier than Japanese plums (Prunus salicina). Generally self-fertile, they bear fruit on fairly long-lived spurs and are less vigorous than the aforementioned plums. They bloom much later in the season (typically with apple trees) and are more tolerant of heavier soils, but are a bit slower to come into production. The fruits are sweeter, smaller, and less juicy than Japanese or American hybrid plums and as such, appear to be considerably more frost-resistant in the fall. The Washington State University orchard in Pullman “Washington, has a number of trees of “President”, a European plum that does not ripen there until late October or early November. During the last three (8) growing seasons, I have noticed that even after exposure to temperatures in the low 20°s overnight “President” prune plums do not turn to mush, but remain firm whether on the tree or off. By contrast seedling Manchurian plums in Dale Halls orchard in Anchorage were badly damaged by frosts in the 28°-to-30°F range in September 1987. Furthermore, at least in Pullman. European plums (“Early Italian”, “Italian”, and “President”) are very reliable croppers, little affected by the same wintertime freeze/thaw/freeze cycles that wreak havoc on peaches, apricots, and sometimes sweet cherries and even pears.
“Stanley”, one of the best known European plums, has survived and even borne fruit in Homer for Fred and Margaret Anderson, but the fruit never ripened-hardly surprising considering that in Geneva New York, “Stanley” is ripe on the average about September 22, and the season there is four (4) weeks ahead of southcentral Alaska. “Stanley” and the Myrobalan rootstock it was grafted to also survived and grew well in west Anchorage for Rich Raynor, a member of this chapter, at least for the period 1984-1989. Are there other European plums that ripen earlier, yet have the required hardiness?
The answer appears to be yea “Mount Royal” has survived and even ripened fruit in Juneau. It is described in the Hilltop Trees’ catalog of Newark Nurseries Inc., as a “very hardy, excellent blue plum that originated near Montreal. Canada. The fruits are medium size, round yellow-fleshed with good quality. The tree is medium in vigor, very hardy, and productive.” The Swedburg Nursery catalog offers some additional comments on “Mount Royal”, calling its fruit freestone, with meaty, tender, juicy, sweet flesh, and adds that it is suitable for dessert and culinary purposes. Furthermore, it can be dried to make prunes. The Hilltop catalog shows the average picking date for ‘Mount Royal” in southwestern Michigan as August 15-30. corresponding to September 30-October 15 for Anchorage, which is quite late.
A better choice, also described in’ the Hilltop catalog, is “Opal”. The Southmeadow Fruit Gardens’ publication, Choice and Unusual Fruit Varieties for the Connoisseur and Home Gardener, states that “Opal” originated as a cross of “Oullins” with “Early Favourite” at Alnarp, Sweden. First marketed in Sweden in 1948, it since has become “the leading quality plum in Swedish markets.” The Southmeadow publication adds that ‘‘Opal” is self-fertile and an excellent cropper. The Hilltop catalog comments that the tree is of medium vigor, semi- upright and hardy. It calls the fruit semi- freestone, medium firm, round reddish-purple with yellow flesh and good quality. Moreover, Alan F. Simmons’ book, Simmons’ Manual of Fruit (London: David and Charles, 1978, 239 pages), which I found in the Ag Science Library at WSU, says that the tree is rather round- headed, fairly dense, and early flowering. According to Simmons, “Opal” ripens in England about the second week of August. In southwestern Michigan, “Opal” is picked July 25-August 5 on the average, which corresponds to September 10-20 in Anchorage.
Hilltop sells one European plum which is even earlier than “Opal”, namely “Earliblue”. It describes it as “the earliest maturing blue plum we know of. Fruit resembles Stanley, but is softer and has shorter shelf life. Good quality and appearance. Sells readily at roadside. Tree is hardy and productive.” The pick date in Michigan, July 20-30, corresponds to September 5-15 in Anchorage. However, I can find no other information about the plum in other references. None of these varieties are patented.
With respect to availability, “Opal”, “Earliblue”, and ‘Mount Royal” are available (wholesale only, in bundles of five  trees) at Hilltop (Newark Nurseries, Inc.; RO. Box 578; Hartford MI 49057; phone -621-3135 or toll free  253-2911). “Opal” on Myrobalan rootstocks is available retail at Whitney’s Orchard & Nursery (contact me for availability at  697-9765 or write me at my new address, 641 Hoffman Road Selah, WA 98942-9532) and at Southmeadow Fruit Gardens, 15310 Red Arrow Highway, Lakeside, MI 49116. ‘Mount Royal” is available from Swedburg Nurseries Inc.; Box 418; Battle Lake. MN 56515: phone (218) 864-5526, and from Farmer Seed & Nursery, a division of Plantron, Inc.; Fairibault, MN 55021; phone (507) 334- 1623.