Year to year changes in productivity, nutrition and suckering of four cherry rootstocks during a 12 year evaluation

Continuous observations on a cherry rootstock trial for 12 years have shown major fluctuations in cropping levels for the cultivars 'Bing' and 'Van' on Colt, Stockton Morello, Mahaleb and Mazzard F 12/1. Pollination and soil type explain some variations but the major differences are due to the genetic character of the rootstock. Young trees on Colt, Stockton and Mahaleb were precocious with only Stockton exhibiting an imbalance with overcropping, smaller fruit and new growth typical of a dwarfing rootstock. Fruit size from Colt trees has been maintained under light and heavy crop loads. 'Van' on Colt greatly over-cropped in year 12 with associated poor leaf development, but some virus interaction is suspected. Flower bud initiation and the resulting fruit set were significantly less for 'Bing' on Colt than for any other stock. Reduced productivity was a possible concern, but increased fruit size was the main response. The flowering of 'Van' was not affected by rootstock. Despite an initial correlation between calcium and cracked fruit from trees on Colt in 1993 there were no relationships in the following season. The higher leaf levels of calcium in trees on Colt were not providing a tangible horticultural benefit. No root suckers were found on Mahaleb or Mazzard trees contrary to higher latitude districts where Mazzard trees proliferate suckers. High sucker numbers on Stockton trees gradually diminished in older trees whereas the reverse applied to trees on Colt.