Hard Frosts Hit Tamahere Avocados — But All May Not Be Lost

Tamahere avocados have been decimated by Jackfrost as locals count the cost of one of the harsher runs of winter frosts experienced in recent years, with some trees dropping virtually their entire crop and others left with brown, frost-burnt foliage just weeks before spring flowering.

Unlike last winter, when many local trees escaped with little apparent damage, this year's succession of sub-zero nights has been enough to expose one of the vulnerabilities of growing avocados in the Waikato. NZ Avocado says significant winter frost can damage fruit, foliage and developing flower buds, while frost during flowering itself can be particularly destructive. The industry's own basic requirements for avocado production suggest no more than "a couple of mild frosts per year", a description that hasn't fitted parts of Tamahere particularly well this winter.

The result is now very visible in local gardens: avocados littering the ground, brown and burnt-looking leaves and understandable concern that trees preparing to flower may have lost much of this coming season's potential. NZ Avocado research highlights just how vulnerable flower buds can be. In one trial cited by the organisation, 93% of examined floral buds on unprotected young Hass trees were severely damaged following a particularly severe frost year.

But all may not be lost. Local social-media discussion has quickly turned from assessing the damage to helping trees recover. One experienced grower's advice is to remove genuinely dead stems, pruning back only until healthy green tissue is found, mulch heavily and encourage the tree back into growth. That's broadly consistent with NZ Avocado's emphasis on maintaining healthy foliage, nutrition and a good mulch layer as trees move towards their important spring growth period. September is when avocado flower buds normally begin swelling and developing, followed by flowering and new vegetative growth through October and November.

Whether Tamahere's battered trees produce much fruit next season may therefore depend on just how deeply individual trees were affected. A brown canopy doesn't necessarily mean a dead avocado tree — and even a tree that produces little or no crop this time around can potentially recover its canopy and prepare for another season.

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