Native plants are rapidly declining in Nepal’s capital, Kathmandu, replaced by invasive species historically introduced for ornamental and urban greening purposes, reports Mongabay contributor Bibek Bhandari.
Botanist Bharat Babu Shrestha said he has observed traditional medicinal plants like the Indian pennywort (Centella asiatica) slowly vanish from Kathmandu over the past decades, displaced by dense, flowering shrubs of Crofton weed (Ageratina adenophora), native to Central and South America.
“There has been no qualitative assessment in Kathmandu, but our observations show that our native vegetation has been dominated and displaced by many invasive species,” said Shrestha, a botany professor at Tribhuvan University, Nepal. He added that research in Nepal’s national parks suggests these invasive species can reduce native species by nearly half, a trend being mirrored in the country’s capital.
According to experts, dominant invasive species in the city include Crofton weed, common lantana (Lantana camara), Santa Maria feverfew (parthenium weed, Parthenium hysterophorus) and blue billy goat weed (Ageratum houstonianum).
A 2024 study found that 48% of observed plant species in the Sanobharyang region, close to protected areas and community forests, were non-native. Similarly, researcher Ronish Pandey, who submitted his master’s thesis on Kathmandu’s plant species composition to Tribhuvan University last year, found that more than half of the 437 species he surveyed in the capital’s green spaces were exotic; 21% of those naturalized species categorized as invasive.
Krishna Prasad Sharma, the 2024 study’s co-author and an assistant professor at Tribhuvan University, said that some non-native species are less harmful, such as jacaranda (Jacaranda mimosifolia) and avocado (Persea americana), since they stay confined to where they’re planted. But many do become invasive by releasing allelochemicals to inhibit the growth of surrounding plants, he said. Botanist Shrestha warned that popular ornamental plants like the common lantana create thick canopies that block sunlight, suppressing and eventually killing native species.
The spread of non-native plants in Kathmandu is exacerbated by urban planning preferences and weak regulations. Experts said authorities often opt for exotic trees like jacaranda and eucalyptus because they need minimal care and have high survival rates for street beautification projects.
Pandey’s research shows parks maintained by the city also favor exotic flowering plants. “It’s because they mostly don’t know what species to select, and the decisions are based on contracts with the lowest bidder,” he said.
Which city institution is responsible for managing these species remains unclear, according to Sunita Ulak of the environment ministry’s Forest Research and Training Center. While regulations have existed since 1972, implementation is lax and invasive plants are openly sold in private nurseries.
To address the crisis, the Forest Research and Training Center issued an 18-point declaration in December 2025, calling for better monitoring of non-native species and streamlined policies. Shrestha stressed that authorities must strictly enforce the recommendations and invest in risk assessments before non-native seeds reach Nepal’s borders.
Read the full story by Bibek Bhandari here.
Banner image: Lantana on display at the botanical garden in Kathmandu. Image by Abhaya Raj Joshi/Mongabay.
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