Plants that are not readily propagated by cuttings may be temporarily nursed by grafting them to roots or cuttings of more ready-rooting subjects. A simple form of this is to inarch a piece of root into the base of a stem cutting (Fig. 90) and to plant the cutting in the normal way. When roots have developed on the shoot the plant is lifted, the nurse root cut or broken away, and the rooted shoot replanted. Variations of this technique will readily suggest themselves.
It is now acknowledged that nurse grafting has a much wider application than merely supplying temporary roots. By grafting a short piece of one-year-old seedling apple root upon the apical end of a root cutting of a very shy-rooting apple, the root cutting is made to root successfully. Floor36 nursed hardwood cuttings of apple rootstock M9 with pieces of seedling root and obtained buddable plants in the same season (Fig. 91). Nursing can therefore be supplied by root or shoot – basally, apically or laterally. Garner and Hatcher, in the course of their vegetative propagation studies, placed scions of related and unrelated species on apical ends of stem cuttings and found a correlation with leaf-activity rather than with botanical relationship. Leafless cuttings of Citrus species which have otherwise failed to root have been induced to do so by grafting upon them leafy scions. Success here depends upon the retention of leaves by the scion.




Fig. 90 Nurse grafting
Three methods of attaching nurse roots to stem cuttings. The composite cutting is planted in the normal way and, if desired, the nurse roots may be removed when the stems have established their own root system.

Additional leaves The writer found that leafy autumn cuttings of the apple rootstock Malling Crab C, side veneer grafted in their internodes with six individual leaves of the same clone, developed twice as many roots totalling three times the length of those non-grafted. A very shy-rooting crimp-leafed genetic dwarf Prunus avium, given additional leaves of P. mahaleb, rooted vigorously. Summer cuttings of this same genetic dwarf dropped their own leaves and failed to root but rooted vigorously when nursed with individual leaves of the evergreen Prunus laurocerasus (Plate 16). The roots were reminiscent of those generally associated with high mycorrhizal activity. Graft incompatibility, partial or complete, does not appear to reduce nursing powers; on the contrary, complete incompatibility may be an advantage as it ensures their eventual shedding at the junction in the absence of a normal abscission layer. Leafless hardwood cuttings of the apple rootstock M9 were each given six additional leaves of P. laurocerasus at the end of January and placed under mist (Plate 16) alongside cuttings similarly wounded, tied and sealed. When photographed in March those with additional leaves had rooted better than the controls.




16. Additional leaves aid rooting
Leaves of Prunus laurocerasus grafted on hardwood cuttings of apple M9 in January (above) and placed under mist till March rooted better than control cuttings with no additional leaves. Softwood cuttings of a shy-rooting genetic dwarf Prunus avium (below) rooted heavily when given additional leaves of P. laurocerasus (A and B). Non-grafted cuttings (C) failed to root.

R.J. Garner
Robert John Garner was born in Fulbourn, Cambridge, in 1907. A scientist at the former East Malling Research Station from 1926 until 1972, he became an international authority on the vegetative propagation of woody plants. He was awarded an honorary MSc from the University of Reading in 1951 and the Veitch Memorial Medal by the Royal Horticultural Society for his outstanding contribution to the advancement of the art, science, and practice of horticulture in 1980.

Former president of the Horticultural Education Association and the Great Britain and Ireland region of the International Plant Propagators' Society and the author of The Propagation of Tropical Fruit Trees (1976), Garner also wrote numerous research papers for technical journals including The Journal of Horticultural Science and CBB's Technical Communications series published by the Imperial Bureau of Horticulture and Plantation Crops. After his death in 1993, East Malling Research Station opened the Robert Garner Laboratory in remembrance of his life's work.

"patrice" a écrit :
Bonsoir.
Je pense qu'il a voulu expliquer que pour les plantes qui n'ont pas une aptitude au bouturage, de faire une greffe qu'on fait affranchir ensuite. La greffe prend, assure le maintient en vie du greffon le temps qu'il prenne le temps de former son propre système racinaore.

Comme l'indique nicollas, une marcotte en fait autant.

Pourquoi se casser la tête? Si on n'a pas un sujet adulte qu'on puisse marcotter. Genre une variété récupérée dans la bourse, on greffe-affranchi ainsi aisément.