STUDIES ON SOME FACTORS CONCERNING THE ROOTING OF GREEN CUTTINGS OF COMMON LILAC /SYRINGA VULGARIS/

1. Effect of the time of propagation upon rooting. In experiments with the cultivars 'Andenken an L. Späth' and 'Mme Florent Stepman' rooting ability of the shoots reached it's first maximum immediately before finishing the shoot growth. In case of unpruned mother plants this coincided with the blooming. At the time of transition of the terminal buds from vegetative to generative state /generally after the end of blooming/, rooting ability dropped to a minimum. If the majority of shoots ended with vegetative buds, this decrease did not occur. Cuttings taken 1–2 weeks after this and any time before the beginning of July rooted again in high percentages. From the first decade of July, the shoot tips finally lost their ability to root regardless of the age of plants, pruning or the percentage of generative terminal buds. Bud differentiation accelerated in July: terminal buds of unpruned plants and those from heavily pruned ones /whose shoot growth ended 1,5 month /later/ reached stage 7 of differentiation almost at the same time, by the beginning of August. It is supposed that this acceleration, as well as the final decrease of rooting ability, have photoperiodical causes.
2. In experiments with cuttings from different parts of the shoot /cv. 'Andenken an L. Späth'/apical cuttings rooted in the highest and basal cuttings in the lowest percentages.
3. NAA, given in talc proved to be the best in 0,8 % concentration for the rooting of cuttings from cultivars 'Mme Florent Stepman', 'Mme Lemoine', 'Maximowicz', 'Vauban', 'La Mauve' and 'Pres. Falliéres', white cv. 'Andenken an L. Späth' did not respond to the treatment.

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