This short paper continues the regular reporting of performance of successive rotations of pine grown on a 15–17 year rotation in the Usutu Forest, Swaziland. Evidence suggests that the mean height of 5–6 year old fourth rotation P. patula is significantly greater than in all preceding rotations. The increase in mean height of 6–10% probably arises from genetic improvement. Factors of hail damage and variable stocking affect the comparison but do not invalidate the significant overall conclusion.

In view of the intensive management of the highly productive plantations on the relatively poor soils at Usutu, namely short rotations, no thinning, and a clearfelling silvicultural system, the data reported here augur well for the sustainability (narrowsense) of plantations more generally.