The Unstoppable Spread of A Dangerous Plant

There are enemies among us; ones we pass by every day, oblivious to the havoc and destruction they cause. They appear harmless but can be described as modern-day colonisers. If not eradicated or at least controlled, they may inflict irreparable damage on our fragile ecosystem.

Their name? Leucaena leucocephala (pronounced Lucina), a fast-growing plant native to southern Mexico and northern Central America (Belize and Guatemala). Now widespread throughout the tropics, including Saint Lucia, this seemingly innocent plant poses a serious danger.

Assistant Chief Forestry Officer Pius Haynes told St Lucia Times that while settlers introduced the plant, its harmful environmental impact became evident only in the past decade, largely due to deforestation and land clearing for construction.

“This plant was introduced to Saint Lucia many years ago and right now it is causing a serious problem in terms of smothering and taking over most of our indigenous plant species, especially in dry forests,” he says. “What we have noticed about the Leucaena is that whenever an area is open, whenever an area is denuded of vegetation, it is one of the very first species that will emerge. It will eventually colonise the entire area and create what we refer to as a monoculture, with only that species growing there.

“Now, that is something extremely devastating and damaging for wildlife conservation. It simply does not augur well for wildlife conservation.”

Haynes elaborated that indigenous wildlife depends on diverse plant species for sustenance, food, nesting and shelter.

“Since the Leucaena is an invasive plant, an invader, it does not provide the enabling environment for our animals, flowers and even fauna to flourish,” he warns. “As a result, you now see large patches of Leucaena only. In the future, this could lead to the extinction of some of our local flora and fauna.”  

Originally valued for its high biomass—ideal for charcoal production due to its intense heat—and as forage for livestock, the plant’s rapid spread now outweighs its benefits.

Haynes says the Leucaena has spread like wildfire. “It is very prolific and produces a high seed load. Additionally, when cut, it can coppice and regrow quickly, sometimes sprouting five or six shoots from one stem. It’s something we really need to control.”  

As more land is cleared for residential, commercial and tourism development, Leucaena takes over these spaces before human inhabitants can.

“Once areas are cleared, the Leucaena seeds are among the first colonisers, spreading rapidly,” Haynes notes.

Human activity and construction machinery further accelerate its dissemination.

“This is a huge challenge, exacerbated by the culture of deforesting and opening new areas for development,” Haynes says, adding, “It cannot grow where you have a forest that is already covered and established. It can only thrive in an open area.”

So how can its spread be stopped?

“We have a huge fight on our hands,” he concedes. Managing it requires a multi-faceted approach – biological controls, mechanical removal and, where applicable, chemical applications.

And all hands on deck: communities, farmers, property owners, and the government, Haynes stresses.

He advocates for a strong policy response, recognising the threat to biodiversity.

“It has to be a policy decision at the highest level,” he says, and will require legislation mandating eradication.

But he warns it will be an expensive long-term effort, as even after removing mature plants, remnant seeds remain in the soil.

Meanwhile, the Forestry Department continues public education on biosecurity and the risks of introducing invasive species.

Notably, a 2010 project, the National Invasive Species Strategy for Saint Lucia (authored by Gaspard Michael Andrew & Lyndon John), listed Leucaena as an invasive plant, underscoring the urgency of action.