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Kalanchoe × houghtonii, an invasive hybrid that threatens to colonize the new volcanic stream on La Palma

After the devastating volcanic eruption that put the island of La Palma on the news all over the world, it seems that calm has returned to this little corner of the Atlantic.

The new Cumbre Vieja volcano, la Palma, Canary Islands, 2022.

The new Cumbre Vieja volcano (2022). Author: Iván Pérez.

The rivers of lava, previously fiery red, have turned to the characteristic black basalt of the badlands, dotted with the white of the lichens and the green of the vegetation. However, something has changed, and it is that if a few decades ago they were Rumex lunaria L., Aeonium sp., Kleinia neriifolia Haw. or pine (Pinus canariensis C. Sm. ex DC.) the first phanerogams that opened the way to the rest of the plants, the arrival of invaders has put other species at the head. These include the well-known crimson fountaingrass (Pennisetum setaceum (Forssk.) Chiov.) and a new threat, the invasive hybrid Kalanchoe × hougthonii D.B. Ward, very problematic in the peninsula and a specimen that the XenoPlants research group has been studying for a few years.

Stereocaulon vesuvianum-San Juan-volcano, Kleinia neriifolia-Teneguía, Aeonium davidbramwelii-Teneguía, La Palma, Canary Islands

A. Rumex lunaria and Kleinia neriifolia on the slope of Teneguía volcano (2017). B. Stereocaulon vesuvianum Pers. lichen in the San Juan volcano volcanic stream (2019). C. Aeonium davidbramwelii fblooming in the badlands of Teneguía volcano (2017).
Author: Iván Pérez.

This succulent plant seems to be designed to conquer dry environments, being increasingly common on the coasts of Mediterranean climate. But to our surprise, we found seedlings of this invasive growing on the sand emitted from the heart of the island in the past months. Also known as “mother of thousands” or “mother of millions”, it grows comfortably between the rock and the newly formed sand and, although it is not yet as frequent in the Canary Islands, it is increasingly easier to find it outside gardens, competing with the local flora.

Kalanchoe-houghtonii, Cumbre Vieja, volcano, La Palma, Canary Islands

D. Adults of K. houghtonii growing near the Tajuya viewpoint, El Paso (2022). E. K. houghtonii propagules growing on the sand emitted by the volcano (2022).
Author: Iván Pérez.

In this case, some adult specimens were located less than 20 km from the volcanic cone, coexisting with the Forsskaolea angustifolia Retz. grass, a Canary endemism present in all the islands. This should serve as a warning sign, since in other archipelagos of volcanic origin such as Hawaii, the Kalanchoe genus has managed to invade even the most remote places. The great production of propagules by the leaves, added to their CAM metabolism, makes these plants true fighters for survival, their eradication being certainly complicated since a single individual can produce hundreds of clones.

From the Botanical Institute of Barcelona, we send all our support to La Palma, especially to those that have lost so much to this catastrophic and impressive natural event. Let’s hope that nature will allow a satisfactory economic and ecological recovery as soon as possible, and that the badlands created by the unnamed volcano will not become the home to the harmful invasive flora.

Author: Iván Pérez-Lorenzo

Nomenclatural type catalogue