Dwarfing rootstocks for sweet cherries

By analogy with M.9 for apple, the objective with sweet cherries is to find a dwarfing rootstock that makes it possible to obtain trees which yield precociously and which are of reduced stature, so facilitating the harvest of all of the cherries when standing on the ground. Limburgse Boskriek (Prunus avium) was and is the most used rootstock for sweet cherries in Belgium. It has strong vigour and produces good fruit size. However, Limburgse Boskriek is slow to establish and begin cropping, which makes it unsuitable for replanting in new orchards. Even though in most places good results were obtained with this rootstock, it is no longer generally recommended. Colt is a hybrid between Prunus avium and Prunus pseudocerasus. It has a moderately strong vigour and, compared with Prunus avium rootstocks is less susceptible to soil sickness and reacts better to root pruning, which can be explained by its relatively superficial and fine roots. However, this kind of root also has disadvantages, as they make Colt more susceptible to drought stress and absorb nitrogen, potassium and phosphorus less easily. Gisela 5 is a hybrid between Prunus cerasus and Prunus canescens. It is a rootstock with moderate to weak vigour. The production efficiency of Gisela 5 is very high, with very good fruit sizes overall. In dry circumstances cherries can sometimes remain too small on Gisela 5. However, this can be solved quite easily by irrigation of the trees. Like the other two rootstocks, Gisela is suitable for most modern scion varieties. This rootstock is best suited for intensive cherry culture. The original aim, to obtain a smaller tree, easier to control, has been achieved with Colt as well as with Gisela. Because the production-efficiency is highest with Gisela 5, we give preference to this rootstock. These trees come into production earlier, which should shorten the time needed to reach break even on the orchard investment. It is also easier to intensify and to cover the trees against rain and birds with Gisela 5.