by Mark Weaver
In last year’s ranetka article, I voiced concerns about the hardiness of the ranetka seedlings many of us have been using for rootstock. I have since found additional information that helps to answer the question of what “ranetka” is, where it comes from, and how much variability we can expect.
Lawyers Nursery has confirmed that the seedlings APFGA has been purchasing come from the Kiev region of Ukraine (formerly part of the Soviet Union). The following descriptions are translations from various Russian sources that have recently become accessible on the internet. Emphasis has been boldfaced.
From The Great Soviet Encyclopedia, 3rd Edition (1970-1979):
Ranetki: Small-fruited varieties of apple obtained by crossing the Siberian crab apple (or its hybrids) with European varieties or with the Chinese apple. Characteristics of the Siberian crab apple predominate in Ranetki: they are winter-hardy and early-maturing, and they produce large yields every year. Ranetki are used in the selective breeding of apple trees. The fruits are eaten fresh or in processed form. The seeds of some varieties are used for raising stocks [rootstocks?]. In Siberia and the Soviet Far East, the following varieties are common: Purple Ranetka, Altai Amber, Pudovshchina Seedling, and Invincible Grellia. http://encyclopedia2.thefreedictionary.com/Ranetki
And from an unidentified horticultural article:
Ranetka purple: It is believed that this is a hybrid [of Siberian] with a large-fruited variety. Introduced in Siberia in 1892 from North China by Minusinskoye gardener M.G. Nikiforov, who spread it across Siberia. Frost resistance of wood and flower buds is very high. The variety is resistant to scab. Fruits in the 2d-3rd year, and yields are stable. The tree is vigorous with hemispherical and dense foliage. Fruits are small (9 g), flat-round, ribbing is very weak. Peduncle length 3.1 cm. The background color is not visible; the fruit surface is completely covered with a dark purple blush. The flesh is firm, juicy, reddish, often with red veins. Fruits are unsuitable for fresh consumption; they are used only for processing. They contain large amounts of vitamin C (up to 28 mg%). Use fruit in early September, as they can be stored for not more than a month. The advantages of this variety are its exceptional hardiness and yield. http://okul.selyam.net/docs/index-172004.html?page=31
Thus, it now seems certain that “ranetki” and “ranetka” are generic Russian terms for numerous hybrids that have the Siberian crab as one ancestor. They are in effect seedlings of seedlings. Whatever their merits as producers of “berry-apples” for juicing, there can be little doubt that they are variable and cannot all be assumed to provide reliably hardy rootstock under Alaskan conditions.
As the accompanying photographs make clear, the ranetka we have been purchasing from Lawyer’s Nursery vary greatly in vigor, growth habit, fruit shape, and fruit color. More to the point, they almost certainly confer different degrees of hardiness on the wood grafted onto them, and they appear to cause trees of the same cultivar to harden off at different rates. This is an example from my Wasilla orchard:
In the spring of 2012, I planted two nearly identical Heyer 6 yearlings in my “nursery” row. Both were 2-ft. pot-grown trees from pieces of a single length of scionwood (obtained from Dwight Bradley’s Chugiak orchard). Both had been grafted onto ranetka seedling rootstocks from Lawyers. Because I intended to move them eventually to a more permanent location, I planted the trees only 3 feet apart. During the growing season, they received similar fertilization, irrigation, and general maintenance. Although one appeared to be slightly more vigorous than the other, they both went into the difficult winter of 2012-2013 in excellent health.
The less vigorous Heyer 6 tree survived the winter with no signs of injury. It sprouted leaves in the spring of 2013, grew normally, and is still healthy today. The other Heyer 6 tree—only 3 feet away!—suffered frost injury so severe that when I checked it in June 2013, the top was totally dead.
Heyer 6 is a notably hardy cultivar, but it seems obvious that variations in the ranetka rootstock caused one of these trees to be significantly hardier than the other during some critical period of the 2012-2013 winter. After checking temperature records, I have come to believe that the critical period was October 2012.
The early part of that month was remarkably mild, with numerous nighttime lows above 40°F. Then temperatures descended precipitously into the teens, and on October 23, reached a low of about 11°F. Apple trees depend on chill period more than on dwindling day length to alert them to the onset of winter; it is temperatures in the 30s that cause them to stop growing and to harden off. But there were hardly any chill days during early October, and I suspect many normally hardy trees missed their cues and simply did not harden off quickly enough to prepare for sub-freezing temperatures. A difference of a few days’ reaction time may have been the difference between healthy survival and severe injury. Variation in rootstock—which is known to influence vigor as well as how quickly a tree responds to the warning signs of autumn—would easily account for such a difference.
So, for obvious reasons, I am looking forward with interest to the cooperative rootstock trials that APFGA has helped to facilitate at the Alaska Plant Materials Center. May the winters be hard, the survivors tough, and the selection rigorous!