Hidden threats in Beautiful Flowers: Invasive Species in Ireland

Montbretia in Ireland: Troublesome Beauty 

Montbretia (Crocosmia X crocosmiflora) is an invasive perennial plant originating from underground corms. It is a horticultural hybrid developed in France during the 1880s by crossing two South African Crocosmia species for ornamental purposes. Since its creation, Montbretia has escaped into the wild and rapidly spread throughout Europe in the latter half of the 20th Century. It has notably established itself in Ireland, thriving particularly in the mild and damp conditions of the west and south-west regions. Its adaptability is evident in its spread across diverse habitats, including wet grasslands, gardens, hedgerows, pastures, waste areas, and roadsides. 

This plant stands out with vibrant grass-like leaves emerging in spring, clustering near the base. From July to September, distinctive trumpet-shaped orange-red flowers with yellow centres bloom on zig-zag spikes. This plant typically reaches a height of 30-80cm. Capsules turn brown as they mature in autumn, and remnants of dead leaves, stems, and seed heads persist during winter. 

Montbretia’s invasion has a significant impact on ecosystems, particularly due to its competitive edge against Irish native plants. Once established, it dominates local flora, forming dense stands that smother ground cover plants and inhibit indigenous seedlings. This invasive plant’s adaptability to diverse conditions, including frost, heat, and grazing, enables it to thrive across various habitats. Montbretia’s consumes fertilizers and water at the expense of crops. Its remarkable ability to establish from small root fragments further accelerates its spread, exacerbating the displacement of Irish native species and magnifying the disruption to biodiversity. 

Eradication methods involve non-chemical or chemical treatments, necessary because of Montbretia’s ability to regenerate from corms and rhizome fragments. Vigilant handling and disposal prevent further dispersal, as small plant fragments can unintentionally spread. Removal just before full summer flowering is most effective. Continued effort and follow-up are crucial over years to manage corm and rhizome regrowth.

Himalayan Balsam: A Biodiversity Hazard

Himalayan Balsam (Impatiens glandulifera) is an invasive annual plant species coming from Pakistan and the Indian Himalayas. Since its introduction to Europe in the mid of the 19^th century as an ornamental garden plant, it has spread into the wilderness and is now found everywhere in Ireland. Its preferred habitats are damp soil areas, damp woodlands and especially riverbanks. Because of this, Himalayan balsam plants are among the causes of riverbank erosion and increased flood risk. 

Himalayan Balsams also represent a threat for the local biodiversity, specifically, due to their rapidity in growing and spreading even more quickly, they prevent native plants from developing and establishing, colonising all the surrounding area. Additionally, at the end of their life cycle in autumn, Himalayan balsam plants die, leaving a bare, weak soil, particularly susceptible to erosion. 

The seeds of Himalayan Balsams germinate from early March to June and the plant itself can reach the height of 2.5 meters. It is easy to recognise because it is characterised by a pink-red, brittle, hollow stem, slightly translucent and easily breakable. The leaves are elongated and of a dark green hue, and originate from the side branches that emerge from the central stem of the plant. 

The flowering period is from June to October, and the flowers can be identified thanks to their bright pink-purple colour and characteristic English policeman’s hat shape. Studies proved that due to the flowers’ high nectar production, Himalayan Balsam plants can become more attractive to bumblebees, leading to less pollination of the indigenous species. 

Despite their beauty, their main threat is hidden in the green seed capsules that can produce up to 2,500 seeds per plant. If disturbed, the pods explode, and the contained seeds can be propelled up to 7 meters from the plant that originated them. As they can remain viable for up to 18 months, they are easily spread by wind, wildlife and in water. This is why it is important not to eradicate them after June, when flowers are already fully formed. 

Both non-chemical and chemical solution can be used to get rid of the plant. Among the non-chemicals, grazing and trampling by livestock is a successful way to remove the species, especially on a larger scale. However, if you want to offer your personal contribution in removing this invasive plant, the most recommended way is hand-pulling. In fact, due to the Himalayan Balsam’s weak root system, it is very easy to pull the plant up from the ground. To dispose of them, the best way is either composting or air drying on a dry, non-permeable surface. 

To fight these invasvie species, Good Energies Alliance organise “Climate Action Days” in schools around Leitrim, focusing on specific topics ! See more of the previous Climate Action Days here.

References:

Invasive Plant Information Note, Department of Agriculture, Food and the Marine 

Biodiversity Maps, National Biodiversity Data Centre

https://invasivespeciesireland.com/