Fruit tree propagation
Fruit tree propagation is usually carried out vegetatively (non-sexually) by grafting or budding a desired variety onto a suitable rootstock.
Although this is desirable in terms of producing novel combinations from the richness of the gene pool of the two parent plants (such sexual recombination is the source of new cultivars), only rarely will the resulting new fruit tree be directly useful or attractive to the tastes of humankind.
Therefore, from the orchard grower or gardener's point of view, it is preferable to propagate fruit cultivars vegetatively in order to ensure reliability.
This involves taking a cutting (or scion) of wood from a desirable parent tree which is then grown on to produce a new plant or "clone" of the original.
However, although this works well for some plants (such as figs and olives), for most fruit tree cultivars this method has much too low a success rate to be commercially viable.
Grafting is a preferred method because it not only propagates a new plant of the desired hybrid cultivar, it usually also confers extra advantages as a result of the characteristics of the rootstocks (or stocks), which are selected for characteristics such as their vigour of growth, hardiness and soil tolerance, as well as compatibility with the desired variety that will form the aerial part of the plant (called the scion).
Two of the most common grafting techniques are "whip and tongue", carried out in spring as the sap rises, and "budding", which is performed around the end of summer.
The Malling series and clones have been standard rootstocks for apples for many years and remain the "workhorses" for the commercial industry in the United States[3] and the UK.
However, since most of them are susceptible to disease some Malling rootstocks are being replaced by new breeds, including the Cornell-Geneva series, which has resistance to the major problems preventing quality production of apples utilizing organic control systems.
[3] Another, the G.30, has proved to be an excellent stock for production but it was only after a number of years of trials that it was found to be somewhat incompatible with the cultivar "Gala", so that it is now recommended to be staked and wired.
This information has the potential to create economic benefits to both growers and consumers, as well as helping to reduce the need to spray pesticides as frequently as is currently required.
East Malling Research Station in Kent, England collected clones of the Paradise stocks from France in 1912 from which 24 "M" were designated with no particular order to the rootstock characteristics other than where they were located in the garden at the time the numbers were assigned.
[1] "MM" designates Malling-Merton stocks developed from joint breeding program by John Innes Institute, in Merton, England, & East Malling Research Station in the early 1950s.
[11] "EMLA" designates East Malling / Long Ashton research stations who took the "M" stocks and developed virus free versions.
[1] "CG" or "G" designates Cornell-Geneva stocks which are those developed via the Cornell and USDA collaboration at the New York Agricultural Experiment Station in Geneva, NY.
Varieties that require double working include "Bristol Cross", "Dr Jules Guyot", "Doyenné d' été" and "Williams Bon Chrétien".
However, even for fruit trees that usually are grown grafted on a rootstock, there can be advantages in growing them on their own roots instead, particularly in the traditional coppicing systems advocated in both sustainable agriculture and permaculture.
[20] The research undertaken at Brogdale did not continue but there has been renewed academic interest in own root fruit trees since the turn of the century.
Family trees typically combine several cultivars (two or three being most common) of apple, pear or a given species of stonefruit on a single rootstock, while fruit salad trees typically carry two or more different species from within a given genus, such as plum, apricot, and peach or mandarin orange, lemon, and lime.
