The Chilean Nasturtium, scientifically known as Tropaeolum ciliatum, is raising more and more questions among gardeners. Is it an invasive plant to be feared in our gardens? While its vibrant flowering and ability to quickly cover structures make it attractive, its invasive potential can pose problems. This article aims to inform gardeners about the risks this climbing plant may represent in terms of garden invasion and effective management methods. So, should we be concerned about the Chilean Nasturtium? Let's take stock.
What is the Chilean Nasturtium?
The Chilean Nasturtium (Tropaeolum ciliatum) or Indian Cress is a climbing plant native to South America, particularly found in the mountainous regions of Chile and Argentina and therefore hardy down to -15 °C. Its yellow tubular flowers have a unique shape that easily distinguishes them from those of other nasturtium species. The stems of Tropaeolum ciliatum are voluble, allowing the plant to wrap around various supports, and are covered in fine hairs that give it a distinctive texture. The leaves are palmate, meaning they are shaped like a palm, adding to the plant's aesthetic with their lush green appearance and symmetrical arrangement.
Compared to the Greater Nasturtium, beloved in our gardens, the Chilean Nasturtium has several notable differences. The flowers of Tropaeolum majus are generally larger and can vary in colour from bright red to orange and yellow, while those of Tropaeolum ciliatum are exclusively yellow and more tubular in shape. In terms of growth, Tropaeolum ciliatum has a marked climbing habit, using its voluble stems to climb on supports, whereas the Greater Nasturtium often adopts a more trailing or creeping habit.
Nasturtiums are charming and easy-to-grow plants. To learn more, read Nasturtium: sowing, planting, and maintaining.
A rather invasive character!
The Chilean Nasturtium or Nasturtium is a plant known for its vigour and rapid growth. In a short time, it can spread significantly, covering large areas with its voluble stems. This ability to climb and spread makes it an ideal plant for dressing trellises, pergolas, or fences, but it can also pose a problem if not controlled. In favourable environments, particularly in temperate regions with well-drained soils, Tropaeolum ciliatum can quickly become invasive. Worse, in gardens where it is left unchecked, it can smother other plants competing for light and nutrients. Additionally, its tendency to self-seed adds another level of difficulty, as new plants can appear in unwanted areas.
Invasive or not?
To clarify, an invasive plant is an exotic plant species that spreads rapidly in a new environment, often to the detriment of local species. It can disrupt ecosystems, reduce biodiversity, and cause economic and environmental damage.
Regarding its official status, the Chilean Nasturtium is currently not recognised as an invasive plant in France and Belgium. However, this does not mean that gardeners should not be concerned. While the lack of official recognition indicates that it has not yet shown significant ecological impact on a large scale, reports from local gardeners suggest that it can exhibit invasive behaviour under specific conditions (temperate climate and well-drained but cool soil). It is therefore crucial for gardeners to stay informed and adopt appropriate management practices to control its development and prevent any potentially invasive situations.
How to manage my Chilean Nasturtium?
Regular pruning of the stems is essential to limit its expansion and prevent it from covering too large areas. This practice helps control its growth and keep the plant within desired limits. Additionally, monitoring spontaneous seedlings (and manually removing them) helps prevent new plants from establishing in unwanted areas.
Alternatively, growing in pots is a practical solution that allows for easier control of the plant's growing space and reduces the risk of spreading. Using trellises and supports to direct vertical growth can also limit the space occupied by the plant while benefiting from its aesthetic appeal.
Chilean Nasturtium: stop or go?
The question of whether to continue planting the Chilean Nasturtium in our gardens deserves careful consideration. This plant boasts abundant and beautiful flowering, which can bring a vibrant touch of colour with its yellow tubular flowers. Furthermore, its ability to quickly cover structures makes it an ideal solution for enhancing trellises, pergolas, or fences in no time. This characteristic is certainly appreciated in gardens where a decorative and lush effect is desired quickly.
However, planting Tropaeolum ciliatum requires a certain level of vigilance and maintenance. Gardeners must be prepared to closely monitor the plant's growth to prevent it from becoming invasive. Regular pruning of the stems and removal of spontaneous seedlings require time and attention. This plant may therefore not be suitable for all gardeners, especially those seeking less demanding options in terms of maintenance.
In other words, the Chilean Nasturtium is not a plant to be categorically crossed off the list, but there are so many alternatives among climbing plants that it would be a bit foolish to insist on planting it when one knows its behaviour. For now, it is not recognised as invasive (at least not officially), but caution is warranted: so let's plant something else if possible!
Want to learn more about mastering the climbing Chilean Nasturtium? Check out our video with Michaël and Olivier, who present it in detail!
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