Some factors affecting stability.

• Lack of wind stress when young, this is a problem which can occur when trees are over 1 m tall when planted, and then are staked for too long. Deep well-drained soil and exposure to wind when young encourages the development of a good root system as well as of wood in the stem as hormones are activated which stimulate growth of the cambium.

• Type of soil and the soil compaction affects growth. If soils are heavy clays, then good soil preparation is essential. Some plant roots have difficulty in penetrating clay soils.

• Trees planted in clusters offer mutual support compared to those that are planted in rows, particularly if that coincides with the direction of the strongest winds. This was evident in ‘Yasi’ when rows of trees running across the wind came down but in a row running with the wind then the first ones fell and protected the remainder.

Trees over 1 m tall when planted are liable to go over in strong winds if the root systems are not well developed. The soil type must be considered and the young trees planted correctly.