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.
The pawpaw is the only temperate member of the tropical Annonaceae family and is the largest tree fruit native to the United States. Pawpaws grow wild in the rich, mesic hardwood forests of 25 states in the eastern United States ranging from northern Florida to southern Ontario (Canada) and as far west as eastern Nebraska.