We need to talk about Montbretia!

I have encountered so many people who believe Montbretia is native to Ireland... They spread it willy-nilly in their garden and share the plant with their friends, not realising that it is an invasive alien species and endangers the native flora of Ireland... For the last four years I have attempted to remove clumps of this very pretty plant in my local woodland of Courtmacsherry here on the Seven Heads Peninsula. Montbretia has taken over large swaths of the woodland and i have focused specifically on pulling it out on the edges of the woodland where the ancient oak trees grow and shed their acorn in the autumn, in an attempt to enable young oak saplings to take hold and ensure oak succession in this threatened habitat.

I hope that with this post, people will become more aware of the threats that Montbretia cause to biodiversity and will be sensitised to help in my quest to protect and support the indigenous plant and animal species on the island.

What is Montbretia?

Montbretia (Crocosmia x crocosmiiflora) is a flowering perennial plant belonging to the Iris family. Although it is so widespread that it appears to be native, Montbretia is a hybrid of two South African Crocosmia species and an invasive alien species to Ireland, where it has naturalised and is well capable of sustaining its population.

Undeniably attractive, Montbretia was originally created in France and introduced as a horticultural ornamental hybrid. Widely grown in gardens for its sprays of reddish orange flowers that appear in late summer, Montbretia is extremely invasive and can completely dominate habitat where it grows, sometimes excluding native plant species. It is especially present in the west and southwest of Ireland due to the mild and damp conditions, and invades roadside verges and hedge banks, cliff tops and woodland edges.

How to identify Montbretia

Crocosmia species are easily recognised when in flower by the distinct shape and colour of their flower heads. The hybrid Montbretia - the species which is invasive in Ireland with its relatively short stems and orange flowers, grows to 60cm high with long and narrow pale green leaves arising from the base. From July to September, the plant produces tall arching spikes of reddish-orange funnel-shaped flowers which are one-sided with six lobes and three protruding stamens. The base of the plant is a corm - a swollen underground stem that forms a dense mat of roots and is difficult to shift once established.

So what's the problem with it?

The biodiversity of ecosystems can be significantly affected by Montbretia. The plant out-competes the local flora by smothering ground cover plants and small shrubs with its large dense stands; it also prevents the regeneration of native vegetation by smothering seedlings. Montbretia is not used for breeding by our butterflies or moths and is damaging many protected habitats, including Special Areas of Conservation.

What can I do?

If you see Montbretia in hedges and want to protect the environment, pull the clumps up in early summer before the flower heads form. Report sightings to the National Biodiversity Data Centre and more importantly, avoid spreading the plant to other areas. Montbretia is relatively easy to pull up with a spade, but small fragments of roots can easily separate from the parent plant, so complete removal will have to be worked on over several years. Do not dispose of the material in the compost bin, it must go to landfill. If you are left with a large area of bare soil after the plants are removed, sow native seeds by simply tossing some on the soil surface.

Have you managed to eradicate Montbretia in your neighbourhood? Or you are struggling to come to terms with it in your garden? I’d love to hear about it in the comments!

📷 J. Harding, Chihiro H, Forest and Kim Starr