Christmas tree cultivation tractors, and shaper sheers. Mechanized planters, at a cost of about US$4,000, are not essential but a work-saving luxury for farmers. Farmers can purchase seedlings, the lifeblood of a Christmas tree farm, from nurseries. One farmer in Oregon purchased seedlings for between US$200–300 per 1,000 plants. The farmer, a wholesaler, sold his final products for about $20 each; after the cost of the trees and other expenses, a profit of $2–3 per tree. The best-selling species in the North American market are Scots pine, Douglas-fir, noble fir, balsam fir, Fraser fir, Virginia pine, and eastern white pine, although other types
WAVL tree WAVL tree In computer science, a WAVL tree or weak AVL tree is a self-balancing binary search tree. WAVL trees are named after AVL trees, another type of balanced search tree, and are closely related both to AVL trees and red–black trees, which all fall into a common framework of rank balanced trees. Like other balanced binary search trees, WAVL trees can handle insertion, deletion, and search operations in time per operation. WAVL trees are designed to combine some of the best properties of both AVL trees and red–black trees. One advantage of AVL trees over red–black trees is that