DOC staff and volunteers count seeds from forest samples

Image: Laura Honey | ©


New Zealand’s beech and rimu forests are producing large amounts of seed in 2019. It’s being called a mega mast (seeding).


DOC’s sampling of beech and rimu trees in February and March has confirmed a widespread and heavy beech and rimu mast throughout most of New Zealand. 


Our scientists have predicted it’s the biggest beech mast since 1975 based on an analysis of climate records and what’s known about the link between climate and seeding.

When beech forests seed heavily, they can produce up to 15,000 seeds per square metre or 250 kg of seeds per hectare. This provides a bounty of food for native insects and birds but also for rodents, whose populations can expand rapidly and fuel an explosion of stoat numbers.

How does DOC estimate the size of a mast?

DOC has been sampling beech and rimu forests since 2011 to measure the size of forecast mast events and inform planning for predator control.

This year a DOC team snipped branches by helicopter from more than 8000 beech and rimu trees at nearly 200 sites across the country in the sampling programme. They also checked some 1000 tussock plants at 63 sites.

Back at the office, workers processed more than 43,000 beech and rimu samples and counted over three million seed pods.

Why is 2019 a 'mega' mast?

In 2019, our scientists found beech forests around the country are seeding with particularly heavy seeding in the South Island and a mix of moderate to heavy seeding in the North Island. Tussock grasslands in the South Island are also producing lots of seed.

Fruiting in South Island rimu forests is also heavy and exceptionally so on Stewart Island/Rakiura and in the Catlins and Taramakau valley on the West Coast. In the North Island rimu fruiting is more variable.

Forest seeding areas are highlighted on our maps below:

Estimated seeding 2019
Estimated seeding in 2019

See larger maps

Related links

Viewing files on this page

If you can't view these files contact us to request another format. 

About our files

Back to top