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Ginkgo biloba L. has been used for over 3,000 years in its homeland China for food, decoration and treatment of various diseases. Ginkgo can be propagated by seeds, green and ripe cuttings and by grafting. A major disadvantage in the seed propagation is that the new plants are genetically heterogeneous in terms of morphological and botanical features as well as in the content of biologically active substances in the leaves. Moreover, the signs which distinguish malefrom female plants appear only after 15-20 years – too late for removing the fruiting trees which are undesirable for landscaping purposes because of the bad smell of the fruits. Vegetative propagation is used on the one hand for the production of clones and varieties having desirable decorative qualities and on the other hand – to produce only male trees for landscaping.
The hot callus method of grafting has been optimized for walnut and other trees at the of Fruit Growing Institute in Plovdiv by a specially developed system with water heating. The objective of this experiment was to study the possibilities for grafting Ginkgo by this method. Annual seedlings of Ginkgo biloba L. were used as a rootstock. Scions of appropriate size were taken from a male tree. The cleft grafting was carried out at the beginning of March. The grafted plants were laid horizontally on the tunnels so that the place of grafting be on the heated pipeline. The roots of the plants which were found to be outside the tunnel were covered with damp sand. A temperature of 27°C (± 1°C) was maintained for 4 weeks. After that period the grafted plants were planted in pots with a peat-pearlite mixture. The non-grafted seedlings grown under the same conditions were used as a control. A very high percentage of transplanting – 75%, with very a good development of the grafted plants was reported and the one-year vegetation growth reached 20 centimeters.