The use of feathered trees combined with high planting densities and minimal pruning has resulted in a significant improvement in yield of new orchards over the first 5 years. The larger the initial caliper of the tree at planting, the greater the growth and yield in the first 4-5 years. The greater the number of feathers at planting, the greater the yield especially in the second and third years. Feathered nursery trees are a critical component of most high-density apple planting systems including the Tall Spindle. As the benefits of highly feathered trees were discovered, it became necessary to develop nursery management techniques to stimulate lateral branch development. This desired product led to the development of the two-year branched tree, the two-year knip tree, leaf removal/pinching techniques, fertigation and the use of plant growth regulators such as Promalin, Maxcel, and Tiberon. As these practices and new products have been implemented by nurseries around the world, the quality (caliper, tree height, feather positioning along the trunk, crotch angles, number and length of feathers) of nursery trees has improved considerably over the last 20 years. The number of feathers on US grown nursery trees has also improved significantly in the last decade. Most nurseries used a single spray of Promalin combined with leaf removal to obtain trees with 3-5 feathers. In the spring of 2009 a new branching chemical, Tiberon, was registered, and was used commercially in the Northwest of the US. Its use significantly improved the quality of apple nursery trees. In 2010 we evaluated the use of Tiberon in NY and found that Tiberon sprays to Macoun trees under New York climatic conditions significantly reduced tree height and caliper, and resulted in poor tree architecture. Our results with multiple applications of Maxcel in 2010 and 2011 have been very promising. For the coming years, it appears that the potential use of Maxcel if applied multiple times (3-4 sprays of 500ppm) will help US nurserymen to continue producing highly feathered apple trees similar to the ones produced in the last 3 years with Tiberon (Fig. 5). In Europe, Italian nurserymen use Maxcel for chemical branching of knip-boom trees. Depending on cultivar, Italian nurserymen apply from 3 to 4 Maxcel treatments with spray intervals of 5-7 days depending on temperatures after application. A Maxcel spray works betterfor them when it is followed by a 3 hour period of at least 18°C (65°F). They prefer the use of Promalin to Maxcel only for branching of Red Delicious types. Maxcel has also been shown to be a useful tool if planting whips or poorly feathered trees in NY orchards when the leader is not headed and a Maxcel spray of 500ppm is applied to the leader from the tip down to 24 inches above the soil at 10-14 days after bud break (Miranda Sazo and Robinson, unpublished). The importance of having highly branched trees with good height and caliper is of such critical importance to the success of newly planted high density orchards that continued research of Maxcel rates and timings under different growing conditions (in the west and east in the United States) is very important. It will result in improved techniques for chemical branching of nursery apple trees. There is an opportunity for Maxcel to become a good tool for chemical branching in the US.

The Use of Plant Growth Regulators for Branching of Nursery Trees in NY State (pdf; 6098KB)