Mimosa Invasion: Beloved Garden Plant Threatens Local Ecosystems

With its honey-like scent and fluffy, bright yellow blooms, the mimosa lights up the winter months. Described by Julien Cavatore, a nursery owner in Var, as a “firework announcing spring” during a phone interview, he praises this “generous” and “easy-to-grow” tree. However, its abundance has allowed it to spread, often at the expense of surrounding plant life.

About 60 km from Cavatore’s nursery, Bénédicte Cornuault tirelessly battles the winter mimosa—Acacia dealbata, the most well-known variety among the 1,300 species worldwide. “This tree colonizes very quickly, forming dense thickets that leave no room for local flora to thrive,” explains the expert.

The tree can produce numerous suckers from its root system, and to top it off, it releases toxic substances that inhibit the growth of nearby vegetation.

Working with the Conservatory of Natural Spaces, where she is employed, Cornuault strives to control its spread in the Estérel massif, near Fréjus. “We have streams with wild oleanders and a scrubland with Montpellier cistus, both under direct threat,” she emphasizes. “The local fauna, including the Hermann’s tortoise—a rare terrestrial species in France that requires open habitats—also suffers.”

Native to Australia, the mimosa was introduced to France in the early 19th century by explorer Nicolas Baudin. Planted in the gardens of Empress Joséphine de Beauharnais, the tree quickly became a favorite among perfumers. By the end of the century, it was extensively cultivated along the French Riviera, where the climate is well-suited to its growth.

The plant has so successfully adapted to the Mediterranean basin that it is now considered by scientists as highly invasive. “It is also highly flammable and very allergenic,” adds Cornuault. Consequently, the Conservatory conducts annual cutting and stump removal campaigns to curb its proliferation.

Elsewhere, the tree’s detrimental effects are well-documented. In Cap Lardier (Var), it competes directly with several local orchid species, such as the Provence orchid (Orchis provincialis) and the neglected Serapias (Serapias neglecta). In Portugal, the rapid growth of acacias has significantly reduced both the coverage and diversity of native vegetation.

Despite these issues, the winter mimosa remains a popular choice in nurseries. It is not restricted for sale, unlike the black acacia and blue mimosa. “Only the Acacia mearnsii and Acacia saligna varieties are regulated at the European level,” notes Arnaud Albert, a national expert on invasive exotic plants at the French Office of Biodiversity. “They are forbidden from all activities: introduction, purchase, sale, possession, and use.”

But should we then avoid this vibrant plant? “Not at all,” asserts Julien Cavatore: “It can be invasive but only in acidic, siliceous soils,” he adds. Conversely, on limestone soil, the tree often struggles to thrive.

Moreover, nursery owners claim to have a solution: “We graft the winter mimosa onto other, more suitable and non-invasive acacia varieties,” explains Cavatore, who favors the four-season mimosa (Acacia retinodes) as a rootstock.

The same sentiment is echoed by Myriam Quissac at the Ecological Garden in Gard: “If you buy a grafted mimosa, there should be no problem,” she insists. “But be careful, as the classic winter mimosas from cuttings are much cheaper.” Before rushing to purchase those yellow blooms, it’s wise to check the label!