The use of a higher Gamma (cobalt-60) initial dose rate, with the dose rate decreasing after the polymerization of monomers was begun in maple and birch, produces wood-plastic combinations with the type of property enhancement which has come to be expected for these composites. The use of a decreasing dose rate source is seen to offer certain advantages. One advantage is the obvious savings in the time required to attain the total required dose over the total time required to polymerize either MMA or SAN with a low constant dose rate source as has been recommended for wood-plastic combination production.