The climate of the Okanagan Valley in British Columbia, Canada, is highly suitable for growing tree fruit and wine grapes, both of which are booming industries in the region. Most tree fruit, like wine grapes, are not one whole plant but composed of two parts: the upper portion (scion) that produces shoots and fruit, and the lower rooting portion (rootstock). The scion is majorly responsible for traits such as taste, fruit size and colour and has been the main interest to breeders for developing and improving varieties. Rootstocks, on the other hand, provide cold and drought tolerance, soil adaptability, and disease resistance, yet they are only recently receiving attention, particularly for sweet cherries. Sweet cherries have been grafted onto “Mazzard” rootstock since the times of the early Romans and Greeks and is still the most widely used rootstock in the Pacific Northwest of Canada and the United States.
Several new rootstocks have been up-and-coming in the sweet cherry industry which have improved disease resistance and characteristics more suited to the high-density farming practices that have begun to predominate. These rootstocks have a semi-dwarfing nature and thus the mature trees are smaller, enabling a grower to plant more trees in the same area than they would with larger trees. Another benefit of having a smaller tree is that they flower earlier than larger trees, a trait growers call precocity. The earlier a cherry tree flowers, the sooner it will reach full production. A cherry tree on “Mazzard” may take up to twelve years, while a cherry on a newer rootstock, like “Gisela 6,” only five or six.
Relative size comparison chart of several rootstocks being evaluated by Michigan State University and Washington State University.
“Gisela 6” (P. cerasus x P. canescens)is one of the more vigorous rootstocks, yet is very precocious for a tree of its size. Growers can plant 300-500 trees per acre, and it produces a harvestable crop by its third year. Varieties such as “Bing” and “Skeena,” with low to moderate productivity achieve high fruit quality when grafted into “Gisela 6,” as the flowering and growth habits imparted by the rootstock counterbalance the lower fruit yield of the scion. Pruning during early ages and support during the first fruiting seasons are important for trees on “Gisela 6” in order to maintain fruit quality and prevent the trees from becoming overburdened with its high fruit production.
“Gisela 6” can be planted at 300-500 trees per acre, an attractive feature to high-density growers.
Adequate levels of vigour are necessary to produce high quality fruit on smaller trees, and “Gisela 6” produces new shoots more easily than “Gisela 5,” making it the more popular choice for growers. It is also well adapted to a large range of soil types from light to heavy, with good drainage being essential. Other traits make this one of the most desirable rootstocks, including its bacterial canker resistance, virus tolerance, and scion compatibility.Obtaining enough rootstock for a planting, particularly in high-density orchards, can be challenging.
Realizing the burgeoning demands of “Gisela-6.” FloraMaxx has undertaken its tissue culture propagation. The finished rootstock product is certified virus-free, genetically uniform and have vigorous root systems which improve survival rates once planted in the field. Plants can be produced en mass without being limited by the amount of mother material as can be the case with cuttings. Our plants have been successfully budded by growers in the same year, which means that they can be ready for budding in late summer if they are planted dormant in early spring.
If you are interested in using Gisela-6 as your next cherry rootstock, or would like to learn more, please don't hesitate to contact us.
A one year-old tissue cultured “Gisela 6” has been double budded using the chip method.
(Photo courtesy: Calissi Farms, Kelowna, BC)