Living wood in the tree performs a kind of muscle action generating forces at the sapwood periphery and thus residual strains in the dead sapwood fibres. Dissymmetric force generation around tree trunk is a kind of motor system useful for movement, posture control and tree reshaping after accidents. Rather young trees are able to restore the verticality of their trunk after accidental rotation of the soil-root system due to wind or some landslide, leading to typical basically curved stems shape. The very high dissymmetry of forces for the motor action is associated with the occurrence of reaction wood on one side of the inclined stem during many successive years. A selection of 17 such trees coming from 15 different species (13 different families), tropical or temperate, hardwoods or softwoods, were selected and peripheral residual strains were measured in situ before felling, on 8 position for each stem. Associated wooden rods were sawn and measured for their mechanical and physical properties at green and dry state, allowing the estimation of tree growth stresses i.e. forces created by the living wood. Thanks to the wide range of wood types, species and basic densities, simple and highly significant formulas are found for the relationship between green and dry wood properties such as density, longitudinal modulus of elasticity, specific modulus and two shearing moduli of elasticity. It was also possible to build easy to use conversion coefficients between growth stress indicator (GSI), measured in situ by the single hole method, and growth strain and growth stress with the knowledge of basic density and green longitudinal elastic modulus.