How will the Manuka flower this summer?

Posted on October 31, 2016

New Zealand plant species are quite unpredictable in their flowering and seeding habits, from year to year. The causes of this are still relatively unknown.

The term ‘masting’ has been discussed recently, mostly in relation to the flowering and seeding of New Zealand beech trees. Masting is the intermittent production of large flower or seed crops by a population of perennial plants. In mast years, abundant flowering and seeding often leads to bumper populations of mice, which in turn leads to high numbers of predators such as rats and stoats.

The ‘masting’ cycle may be a natural adaptation of many New Zealand plant species to control seed germination, to reduce the likelihood of overcrowding caused by New Zealand’s naturally favourable climatic conditions. It is also possible that the timing and intensity of masting is being influenced by global climatic change. More frequent hot seasons may trigger more frequent masting, with widespread effects on plant and animal communities.

Studies have shown that masting is caused by higher than usual temperatures during the previous summer and autumn. For example, flower buds of pohutukawa and snow tussock are set before winter.

Among the native plants that have been recorded for masting are beeches (nothofagus), pohutukawa (metrosideros excelsa), harakeke (phormium tenax) and chionochloa (snow tussock). In these species, the flowering time across the whole population is synchronised, and furthermore, this often happens simultaneously across the whole of New Zealand.

It appears that Manuka may also be a ‘masting’ species. The flowering was generally light across most of the country during the 2015/2016 season, especially in the Taranaki region. Last summer was an ‘El Nino’ summer, but generally the summer and autumn temperatures were warm and rainfall occurred at regular intervals.

Early indications in the Far North is that the Manuka is flowering 7-10 days earlier this year  The flowering volume appears to be higher than last year, but the wet spring weather has resulted in a late start to honey flows.

It would be a worthwhile exercise to monitor the flowering of Manuka across a wide range of regions, over several years, to see what patterns may emerge. This would be of much benefit to the New Zealand Beekeeping and Honey industry to enable them to predict and plan for each season.

The New Zealand Plant Conservation Network (NZPCN) has a website to which anyone can record sightings of flowering and fruiting of plants http://www.nzpcn.org.nz/page.aspx?flora_phenology_instructions. You can record specific details of where and when, with a more generalised measure of the degree of flowering or fruiting.