Last year, we “top worked” some Comice pear trees in our orchard—36 to be precise. We saved 12 of these trees to pollinate the Buerre Bosc pears. I planted the orchard five years ago, but the Comice pears have not performed well and seemed unhappy in our microclimate. The Bosc pears, however, took to the microclimate like a duck takes to water. So this winter, I cut some scion wood from the Bosc pears and am going to “top work” the last 12 Comice pear trees. Last year, we grafted the Comice pears over to Conference pears and four Asian pear varieties. The picture in this article is Stephen cutting off the “nurse” limb we left to stabilize the tree from the aggressive pruning.
Top working is a term that refers to grafting a new variety onto an existing tree. In a sense, you are working on establishing a new “top” for the tree. It can save a few years in establishing a new variety and lots of dollars. “Top working” makes sense if you are happy with orchard layout, irrigation tree spacing, and if the new variety is compatible with the existing root stock.
Nurse limbs are designed to allow the tree to funnel energy to the new shoots that have been grafted onto the top of the “stump.” It works well because the “nurse” limbs are lower and the tree begins to put energy into building a new top. In the following spring we come back through and select the best of the grafts and cut off the “nurse” limbs.
Grafting is the process where one variety is grafted into or onto another tree. As mentioned earlier, it can really speed up the process of getting back into fruit production by 2-3 years. It is a relatively straitforward process, but you need to be ready to do it when the weather is right, towards the end of April. You also have to gather the scion wood in the dead of winter and store it at near freezing to keep it dormant.
Scion wood is the wood that is grafted onto the existing tree. We typically use a 4-6 inch piece of wood with 3-4 good buds (buds become the future branches). Amazingly, as the main tree adopts the grafts, they will grow 2-4 feet over the summer. And now we are selecting the best “grafts” from last year to grow the new tree.
If all things go as planned, we should see a small crop next year of Conference pears and a larger crop of Buerre Bosc pears in two years from the “top worked” trees this year.