Nov 25, 2010. /Lesprom Network/. Effective December 15, Swanson Group will reduce plywood production by about 25% due to market conditions, as Random Lengths reported. Swanson Group's plywood plants are in Springfield and Glendale, Oregon, USA. The curtailment will remain in effect for an indefinite period of time. Swanson Group Inc. is a privately held forest products company based in Southern Oregon. Since 1951 the Swanson family has been engaged in the manufacturing of Doug Fir dimension lumber, plywood, veneer and studs.