Our mission to preserve and expand rare pondweed species

Over the past 12 months, we've made great progress in understanding how to best grow and cultivate Long-stalked pondweed (Potamogeton praelongus), a rare aquatic plant, to improve its populations in our canals and wider catchment scale habitats.

In June 2023, our team collected cuttings and a small number of rooted rhizomes from the remaining Long-stalked pondweed populations on the Montgomery Canal. This healthy, yet limited, population resides in the canal just outside of Carreghofa, Llanymynech in Wales. The collected material was then carefully transported to the Rare British Plants Nursery in Builth Wells to begin the propagation process.

Propagation Success

Our research shows that the Long-stalked pondweed is a plant that can be easily propagated from cuttings and small rooted rhizomes. Within just a few weeks, we had enough well-grown plants to share with the National Botanic Garden of Wales and Chester Zoo. This rapid growth is an excellent example of the plant's resilience and the effective propagation methods we've employed.

To ensure the future of this species of pondweed, a permanent backup population is now maintained at the Rare British Plants Nursery. This population can be expanded as needed to support future conservation projects, providing a safety net for this rare species.

Our findings

Our successful propagation methods for Long-stalked pondweed, as part of this study, involved several integrated practices that create an optimal growing environment. The team have found that the plants thrive in non-transparent plastic containers about 60cm deep, allowing them to reach the surface and flower. These containers are placed in bright but indirect light to prevent overheating and algae growth. We use rainwater, which is cleaner and less prone to algae development compared to tap water. Additionally, adding Daphnia, or Common water fleas, and other aquatic invertebrates helps maintain a balanced and clean aquatic environment.

For the growing medium, a mix of clay-based garden soil and commercial aquatic compost, topped with a layer of sharp sand, has proven very effective. Rooted rhizomes are planted directly into this substrate and weighted down with stones to ensure good contact and quick root establishment. Leafy stems, left floating on the water surface, develop roots at each node, which can then be separated and planted individually. This comprehensive approach ensures that the Long-stalked pondweed thrives and can be successfully propagated.

We’ve found that the pondweed enjoys year-round growth, even thriving during the winter months and flowering early in the season. Rooted cuttings can be produced at any time of the year, with the exception of very cold, freezing conditions. This continuous growth cycle ensures a steady supply of healthy plants for propagation and conservation efforts.

Looking Ahead

Our ongoing germination experiments with pondweed fruits aim to assess the feasibility of establishing wild populations using fruits harvested from cultivated plants. This research is crucial as we seek innovative methods to support and expand this rare plant's presence, not only in our canals but also across broader catchment-scale habitats.

We are actively exploring options and identifying suitable habitats for introducing Long-stalked pondweed to areas beyond the canal corridor. Potential sites include built open water reserves, natural wetlands, and local river floodplains. By establishing new populations in these diverse habitats, we aim to enhance the biodiversity of the surrounding ecosystems in Mid Wales and contribute to the resilience and richness of local wildlife.

We still have work to do in ensuring that the populations are secure within the canal, as invasive species do threaten their survival. There is a vital need for the ongoing and extensive management for these species, which we couldn’t do without your support, both through donations and volunteering. If you can help, make a donation , or visit our volunteering opportunities page and search for the Montgomery Canal.

We're really happy about the progress made increasing our understanding of the propagation of the Pondweeds, and would like to thank the Rare British Plants Nursery, Chester Zoo and the National Botanic Garden of Wales for their continued support.