dwarfing rootstock are small and thin, they must be supported by a trellis system. Rows are spaced depending on the height of the mature tree, usually half the tree height plus three feet (approximately 1m). High density orchards are more labor efficient than traditional orchards, as workers do not need to climb ladders during maintenance or harvest Pesticide application is also more efficient, as chemicals can be applied by over-the-row sprayers, fixed in-canopy systems, or other devices that reduce pesticide waste. Tree types and planting systems With the move to higher density plantings, different tree types and planting systems have been developed, and are used around the world. These systems include: Central leader trees are commonly grown in a conical shape, with a central vertical shoot (the central leader), and horizontal larger branches at the bottom decreasing to smaller branches near the top. Central leader trees grown with standard or semi dwarf rootstocks are large and free standing, unlike modern high density plantings. The central leader system has been adjusted in recent years to suit the requirements of modern orchard designs and high density plantings. An example of this is slender spindle. While there are different forms, slender spindle trees have the same tapered design. Top branches are regularly renewed by pruning, or weakened by bending. A less vigorous rootstock is used to limit growth, creating a smaller tree, usually individually staked for support of heavy cropping. Solaxe and vertical axis systems are similar to both central leader and slender spindle, and has been used as a transition from low density plantings to high density plantings. Tree size is determined by rootstock, ranging from semi dwarf to fully dwarf. The trees require a form of support. These systems aim to create an equilibrium between fruiting and vegetative growth, receiving minimal pruning. Solaxe uses limb bending to control vigour, a modification from vertical axis which uses periodical pruning. Super spindle orchard design utilises high density planting, with up to or over 2000 trees/acre. The benefits of high density include high early yields with reduced inputs such as labour due to reduced manual work and the ability to have high output picking during harvest. High density plantings are grown with a trellis system for tree support. Tall spindle shares many of the high density benefits as super spindle, and is a combination of slender spindle, vertical axis, solaxe and super spindle systems.