Secretion of GH by the pituitary into the bloodstream stimulates the liver to produce another hormone called insulin-like growth factor I (IGF-I). IGF-I is what actually causes tissue growth in the body. High levels of IGF-I, in turn, signal the pituitary to reduce GH production.
Site and Spacing. 1  The pawpaw is a small tree that typically grows to about 20 feet high and less broad. 2  In an orchard setting, tree centers should be at least 10 feet apart. Row widths depend on the size of tractors and equipment -- 20 foot rows may be a minimum width.
2.5 - 3 caliper = approx. 10-12ft tall. A clump tree or evergreen tree is measured by height. A clump tree, like a River Birch, is a close group of trees with multiple trunks.A 10-12' Tall Clump River Birch means that the size of the tree will range from 10 to 12 feet tall at the time of planting. clump tree or evergreen tree is measured by height. A clump tree, like a River Birch, is a close group of trees with multiple trunks. A 10-12' Tall Clump River Birch means that the size of the tree will range from 10 to 12 feet tall at the time of planting.