When should material for hardwood stem cuttings be collected?

FAQ
Question: 

When should material for hardwood stem cuttings be collected?

Answer: 

Material for hardwood stem cuttings should be collected in late winter (when the plant material is dormant) from wood of the previous season’s growth.  In Iowa, hardwood stem cutting material should be collected in late February or early March.  Material should be taken from healthy, vigorous plants growing in full sun.