When seeds mislead, weeds succeed: Researchers uncover surprising ways NZ weeds spread

Embargoed until: Publicly released: 2026-06-11 03:00

New Zealand

Grey willow seeds. Photo by Kate McAlpine (Department of Conservation)

New Zealand's weeds spread their seeds in ways that scientists didn't expect, perhaps explaining how they travel so far, according to new research. The scientists looked at hundreds of weeds and found that 44% were spread by a method that was unusual for the type of seed that it had. One example is wilding pines: their seeds have wings to help them fly in the wind, but instead they were found to often hitch a ride on animal feathers, fur, feet, and stomachs. The researchers suspect these unexpected weed seed journeys are even more common than they've observed, and that animals are particularly good at spreading seeds long distances.

News release

From: Moa’s Ark Research

When seeds mislead, weeds succeed: Researchers uncover surprising ways weeds spread

Biologists have long thought that seed traits, such as the presence of wings, are the key to predicting in what way, and how far, weeds can disperse. Now, a trio of researchers have revealed that unexpected modes of seed dispersal are more important than mechanisms predicted by seed traits.

In research to be published in the New Zealand Journal of Ecology Debra Wotton (Moa’s Ark Research and University of Canterbury), George Perry (University of Auckland), and Kate McAlpine (Department of Conservation) have established the critical importance of unexpected seed dispersal mechanisms in explaining the dispersal ability of weeds.

Drs Wotton, Perry, and McAlpine undertook years of detective work gathering data for hundreds of weed species from earlier studies and showed that 44% of these species were dispersed by unexpected mechanisms – ones not predicted by their seed traits. Previously, seed dispersal mode was often predicted using seed characteristics. For example, seeds with wings and feathery plumes are carried by the wind, fleshy berries are dispersed by fruit-eating animals, and some plants even have a built-in “seed catapult”.

Unexpected dispersal modes not only were surprisingly widespread, but they also moved seeds further than dispersal mechanisms predicted by seed traits. “We need to understand how weed seeds are actually getting around in order to predict their spread and their impacts on native ecosystems” said the study’s lead author Debra Wotton.

The scientists found that animals are a key culprit in spreading weeds long distances – not only do they disperse more than 60% of weed species, they can move seeds much further than other mechanisms. Wilding pines are a good example of the unexpected ways that animals can transport weed seeds. Pine seeds have wings that assist with wind dispersal, but they can also hitch a ride on animal feathers, fur or feet, in bird nesting material, and when water birds swallow them. “Our research shows the sometimes-surprising ways that seeds can move around the landscape and highlights the importance of identifying the full range of dispersal mechanisms used by weeds in New Zealand”, Dr Wotton said.

Unexpected seed dispersal mechanisms are probably even more common than the new study found, as they have been rarely studied in New Zealand. Identifying and examining the combined effect of multiple seed dispersal mechanisms is critical to understanding the historic and future spread of weeds. The new research can also be used to identify and manage weed threats to our native ecosystems. Weed species with greater dispersal ability can spread more rapidly, including into newly suitable habitats with a changing environment.