Dr Trevor Olesen says if growers want to hedge macadamia trees before flowering, the best time may be in the first week of winter.

Results of NSW DPI research into the flushing and flowering cycle of macadamias is helping growers decide the timing of tree hedging operations.

Many macadamia producers hedge their tree rows due to concerns that orchard crowding will cause a decline in nut yield, make machinery access difficult and reduce groundcover growth on the orchard floor.

Up to now, this has mostly taken place in Spring, after the nuts have fallen from the trees and after the traditional winter flowering.

But with wider use of ethrel to ensure the nut drop is finished in autumn, many growers are looking to hedge before winter.

This pre-winter hedging runs the risk of reducing flowering if the timing is wrong, says research scientist Dr Trevor Olesen.

Dr Olesen has a background in the canopy management research of lychees and is finding similarities with macadamias.

He has found that flowering in a macadamia tree varies depending on how mature the leaves of the most recent flush are during winter, when flowers are normally initiated by the drop in temperature.

'Going into winter you want the most recent vegetative flush to have hardened off so the next flush starts in winter and produces flowers.

'What you don’t want going into winter is an immature vegetative flush because this can suppress flowering.'

He said pre-winter hedging can have a big impact on flowering because it usually starts a new flush of growth at the branch tips.

'It effectively resets the cycle of flush development, and not necessarily to a pattern that is conducive to flowering.'

Dr Olesen says if growers want to hedge before flowering, the best time may be in the first week of winter so the next flush is in winter, and is floral rather than vegetative.

'The cooler temperatures in winter trigger buds in the tree to be released as flower racemes rather than vegetative stems.'

- PHIL BEVAN

This story appears in Agriculture Today.