In 1914, USDA researchers imported Australian melaleuca seeds into the United States. 100 years later, the fast-growing tree had conquered 500,000 acres of South Florida after being planted to help dry the Everglades

A tree brought to the United States as part of an effort to find useful plants eventually became a major problem in South Florida.

In 1914, the USDA imported seeds of Australian melaleuca, a fast-growing tree with papery bark. Decades later, the U.S. Army Corps of Engineers planted groves of the species to stabilize levees in the Everglades, as per a report.

Melaleuca can grow as much as six feet in a year. At least one pilot also scattered its seeds from the air as part of an effort to dry the Everglades, which was then widely viewed as a “useless” swamp, as per a Popular Science report. About a century after its introduction, the tree had spread across half a million acres of South Florida.

How melaleuca arrived in the United States

Melaleuca was one of many plants collected through the USDA's early plant-hunting program. Beginning in 1897, the department's Office of Seed and Plant Introduction sent explorers around the world to search for crops and other plants that could benefit American agriculture.

By 1922, the explorers had brought more than 51,000 lots of grains, fruits, forage crops, vegetables and plants into the United States over the previous 25 years.

The program eventually became responsible for introducing around 400,000 cultivars, including quinoa, soybeans, mangoes and Meyer lemons.

Some introductions, however, later created unintended problems.

Melaleuca found a new role in the Everglades

The Australian tree attracted attention because of its rapid growth. The U.S. Army Corps of Engineers later planted groves in the Everglades to stabilize levees.

Its fast growth made it useful for that purpose, but the effort also involved spreading the plant beyond those areas.

At least one pilot broadcast melaleuca seeds from the air as part of an attempt to dry the wetlands. At the time, the Everglades were generally regarded as a “useless” swamp.

The tree spread through South Florida

Melaleuca eventually moved beyond the areas where it had been deliberately planted. It spread through South Florida, transforming native prairies and marshland into areas dominated by the tree, as per the Popular Science report.

The species was not the only USDA introduction that later became invasive. The Chinese tallow tree was imported in 1903 in the hope of developing a fuel oil industry. By the end of the 20th century, it had spread through the Gulf states and transformed native prairies and marshes into tallow tree monocultures.

Kudzu, another USDA introduction, also became difficult to control. Botanist David Fairchild later regretted planting the vine at his Maryland estate after it spread over bushes and climbed pine trees.

The USDA's approach eventually changed

The early plant-hunting program reflected a period when American agriculture was looking overseas for crops and plants that could adapt to different environments.

Over the following decades, attitudes toward non-native species changed as the problems associated with some introductions became clearer.

Today, deliberately moving thousands of foreign plant species around the world conflicts with modern conservation goals. The USDA now budgets nearly $2 billion a year to prevent, detect and manage species that originate in foreign countries, as per the Popular Science report.

The legacy of the plant-hunting program is complicated. It helped introduce foods such as mangoes, quinoa, pistachios and Meyer lemons while also bringing species that later became invasive.