Looks can be deceiving

Known commonly as the bloodflower, lantana and trailing daisy (in order) these exotic plants can outcompete native plants and even deplete the quality of soil . Photos by Kesang Choden Bhutia

Lantana

Trailing daisy

We are drawn to colours like moths to a flame, be it glittering gold, flashing Diwali lights or pink cherry blossoms. Perhaps this explains why we like to fill our homes and gardens with plants of all colours, with flowers being the showstoppers that brighten up our living spaces.

You might have heard of the plant that can bear flowers of two different colours — the ‘gulbakshi’ or the four o’clock flower. Sounds fascinating, doesn’t it? But did you know that this is an invasive species?

Invasive species are those exotic species that arrive in a new region, with human assistance (either intentional or unintentional), establish populations and spread to great distances from the place where they were initially introduced.

These species can cause biodiversity loss, compete with native vegetation, affect crop production and can have negative impacts on human health. Worldwide, invasive plants are estimated to cause losses amounting to hundreds of billions of dollars every year.

These species can arrive in a region in many ways. The introduction of exotic ornamental plants like the common water hyacinth, tiny periwinkle, pink morning glory, railway creeper and oxeye daisy in India are some examples of such an exchange.

Unfortunately, some of these already established invasive species are still bought, sold, and planted in gardens and homes. Here are some common invasive plants that adorn numerous gardens disguised as ornamentals:

Tick berry (Lantana camara): Commonly known as lantana, this ornamental shrub is native to the tropical regions of Africa and the Americas. Introduced as an ornamental plant in India in the early 19th century, lantana has since invaded the forests of the Southern Western Ghats, Central India, and Shivalik hills. It poses a risk to biodiversity by outcompeting other species, alters vegetation, threatens agriculture and pastoral production and is known to be toxic to livestock, resulting in huge economic losses. The plant also increases the risk of forest fires and has allelopathic properties — releasing chemicals into the surrounding soil which prevents the growth and germination of other plant species.

Four o’clock flower (Mirabilis jalapa): Native to tropical South America, Mirabilis jalapa is mainly cultivated as an ornamental species in India due to its colourful, fragrant flowers. Commonly known as the marvel of Peru or ‘four o’clock plant’ since its flowers only bloom later in the day, Mirabilis belongs to the Bougainvillea family. Pollinated by the sphinx moth and other nocturnal insects, it needs little to no care once established, which is another reason why it is such a popular garden plant. However, the seeds and roots of this plant are toxic due to the presence of the alkaloid trigonelline and have been known to poison dogs and cats, as well as children. The sap can also irritate the skin after prolonged exposure.

Plumed cockscomb (Celosia argentea): The colourful Celosia argentea is an annual herbaceous plant belonging to the Amaranthaceae family and native to parts of Southeast Asia and South America. Commonly known as the wool flower or cockscomb due to its colourful plume-like flowers made up of innumerable feathery spikes, it is one of the most popular garden plants in India, often being used for flower arrangements and wreaths. It is easy to grow and maintain even in the shade or in poor, dry soil, with flowers that bloom for several weeks. However, since the plant is difficult to remove once established, it acts as a weed and increases weed-crop competition.

Scarlet morning glory (Ipomoea hederifolia): This plant belongs to the morning glory family, with tiny scarlet flowers that stand out against heart-shaped leaves. Native to tropical America, this fast-growing vine has become invasive in India as well as in other countries like Australia, Cuba and Fiji. It is known to aggressively twine around neighbouring plants and its seeds are poisonous if ingested in large quantities by animals or children. This plant is considered a troublesome weed in croplands as well, reducing crop yield in economically important crops like sugarcane, maize, and soybeans.

Nasturtium (Tropaeolum majus): This plant is commonly known as Nasturtium, Indian cress, or monk cress, and its origin can be traced back to the Andes mountain range in Bolivia. It is an annual plant with disc-shaped leaves that perfectly show off bright orange flowers, and is easy to grow. This particular plant is known for quite a few unusual phenomena — firstly, the Elizabeth Linnaeus phenomenon or the ‘flashing flowers’ — the bright flowers are believed to emit small flashes of light during dusk. This was later explained as an optical illusion due to the orange-green contrast of the plant. You might be tempted to bring in these natural spectacles into your home garden. However, a National Mission on Himalayan Studies report (2018-19) declared the species as invasive in parts of North Bengal, making it a risky choice.

Polka dot plant (Hypoestes phyllostachya): Particularly loved for the colourful dotted leaves that lend it its name, this annual flowering herb is considered a weed in tropical climates. Due to its popularity, many varieties have been developed in shades of white, red and pink. One of the top 200 invasive plants in the world, this species is native to Madagascar and is invasive primarily in North-East India.

The commonalities between all these plants are that they are eye-catching and grow fast with minimal maintenance, which make them attractive options for home gardens.

While you might think that growing these plants in your home would not have a larger impact on the surrounding environment, that is not true.

If you do have them in your garden or in pots, ensure proper disposal of clippings and fallen seeds after flowering. Green spaces in our homes also need to be safe spaces for other plants to grow and thrive. So, the next time you go plant shopping, would you choose to buy any of these invasive plants?

(The authors are research fellows at the Centre for Biodiversity Monitoring and Conservation Planning, ATREE)