Bareroot tree - a tree which is going to be transplanted with no soil on or around the roots.
Crotch angle - the angle between the main trunk and side branches. Branches with a narrow crotch angle (i.e. tending to grow closer to parallel to the main trunk, as opposed to straight out the side) tend to be more susceptible to wind and ice damage
Cultivar - a particular tree that has been identified as being superior in some respect(s). It is from here that scion wood is obtained for grafting.
Espalier - the practice of planting a shrub or tree essentially in 2 dimensions, normally training it to some trellis network. More commonly done for fruit trees than nuts.
Fertigation - fertilizing through an irrigation system.
Grafting - The act of attaching scion wood to a rootstock. Field grafting is done to a tree already growing in it's permanent place, while bench grafting refers to grafting to a rootstock that is in a nursery setting, yet to be permanently planted
Root Collar - the junction between the part of the tree that is to be above ground to that belowground. This is usually apparent by looking closely at the area. There might be tiny roots starting just below the root collar, and the bark appearance changes.
Rootstock - Tree to which scion wood is grafted. Usually these are seedlings, although some commercial rootstocks are being produced by tissue culture (in a lab, producing genetically identical specimens.)
Scion - piece of wood that comes from a particular cultivar. This is grafted to a rootstock. The resulting trees are genetically identical (clones) of the original tree (cultivar.)
Seedling - Tree grown from seed. On the average, it will take longer to produce nuts than a grafted tree, but eliminates a source of tree failure, as there is no graft union to fail. In contrast to trees that are grafted, seedlings have more genetic variability from tree to tree.
Sunscald - Tree bark damage from freeze/thaw cycles. The sun warms the bark, sap flows, and then subfreezing nighttime temperatures cause craking in the bark. This serves as a route for various pests to enter the tree, as well as causing direct damage.