Root biomechanical properties during establishment of woody perennials

•Root strength, Young’s modulus and diameter of ten woody perennials were tested.•Root strength-diameter relationships often do not follow a negative power law.•Blackthorn, European Box and Holly show increase in tensile strength with diameter.•Young’s modulus was strongly related to root tensile strength for certain species.•Root water status strongly influences root diameter and hence strength properties. Soil bio-engineering using vegetation is an environmentally friendly solution to stabilise soil slopes. This study investigates tensile strength, Young’s modulus, and root diameter relationships for establishing woody perennials. Specimens of ten woody European shrubs and small trees were transplanted into sandy loam soil to establish for six months. Root tensile strength and Young’s modulus were measured as well as the root length-diameter distribution. The effect of root water status on root diameter was evaluated for Scotch Broom. More than half of the root length for all species was thinner than 0.5mm diameter. Typical tensile strengths were