Sour cherry trees cultivars Debreceni Botermo, Nefris, English Morello and local Sokówka Serocka were densely planted at4x1.4x1.5 and 4 x 2 m, and the leader trained for mechanical harvesting with a self-propelled straddle harvester working in continuous motion. From the 3rd year onward the trees were renewal-pruned. Branches older than 3 years were cut back and replaced by young wood. All the cultivars were suitable for mechanical harvesting, although the trees of 'English Morello' were the most difficult to train because of weak growth and trailing shape. Growth measurements over six years indicated that the optimal planting density for 'English Morello' trees was 4 x 1.5 m, and for the other cultivars 4x2m. The harvester designed at the Institute of Horticulture, Skierniewice, was operated by 4 people and appeared to be able to harvest fruit with 95% effectiveness, delivering about 2000 kg of fruit per hour. Fruit quality was good for industrial processing, but not as good as that of hand-picked cherries suitable for freezing.
A study was carried out of shoot growth and branching, fruit bud setting and fruiting in four sour cherry cultivars: 'Debreceni Botermo', 'Nefris', 'Schatten- morelle' and 'Serocka'. Trees were planted at a high density (4 x 1.5 m), trained with a leader and pruned with the renewal method. A relationship was shown to exist between shoot length and fruit bud setting density. Trees of 'Debreceni Botermo' were found to be the most vigorous, setting fruit buds on weak shoots and two-year-old spurs. 'Nefris' and ' Serocka' were medium in vigour, setting fruit buds mostly on one-year-old shoots irrespective of shoot length. They were characterized by heavy branching. 'Schattenmorelle' trees were small, slowly growing, setting fruit buds on one-year-old shoots with only one terminal leaf bud. This type of fruiting led to bare wood. Pruning appropriate to tree morphology is suggested.