Esthwaite Waterweed (Hydrilla verticillata)
Key Details
| Taxonomic Groups: | Vascular plant > flowering plant > Aquatic plant |
| Red List Status: | Vulnerable (Not Relevant) [VU(nr)] |
| D5 Status: | Included in the baseline Red List Index for England (Wilkins, Wilson & Brown, 2022) |
| Section 41 Status: | (not listed) |
| Taxa Included Synonym: | (none) |
| UKSI Recommended Name: | Hydrilla verticillata |
| UKSI Recommended Authority: | (L.f.) Royle |
| UKSI Recommended Qualifier: | (none specified) |
| Red List Citation: | in Stroh et al., 2014 |
| Notes on taxonomy/listing: | (none) |
Criteria
| Question 1: | Does species need conservation or recovery in England? |
| Response: | Yes |
| Justification: | This species has not been seen at its sole English site (Esthwaite Water) since 1941 and is therefore assumed to be regionally extinct in England. However, this is a difficult species to survey and so it may possibly still occur there. As such, it is a candidate for recovery actions in England. |
| Question 2: | Does recovery/ conservation depend on species-specific actions? |
| Response: | Yes |
| Justification: | Recovery will require improvements in water quality followed by ex situ cultivation and reintroduction to Esthwaite following a survey (eDNA, underwater) to establish whether it is still present. |
| Question 3: | At a landscape scale, would the species benefit from untargeted habitat management to increase habitat mosaics, structural diversity, or particular successional stages? |
| Response: | No |
| Justification: | Recovery of this species will rely on site-specific measures. |
Species Assessment
| Current step on the Species Recovery Curve (SRC): | 2. Biological status assessment exists |
| Recovery potential/expectation: | Low - Relict or natural rarity |
| National Monitoring Resource: | Opportunistic - insufficient |
| Species Comments: |
Key Actions
Key Action 1
Proposed Action: Underwater or eDNA survey of Esthwaite Water to establish whether the population still survives.
Action targets: 3. National Monitoring Plan agreed and implemented
Action type: Targeted monitoring
Duration: 1 year
Scale of Implementation: 1 site
High priority sites: Esthwaite Water
Comments:
Key Action 2
Proposed Action: Trial ex situ cultivation from material (turions) collected from Bargatton Loch in Scotland.
Action targets: 5. Remedial action identified
Action type: Ex situ conservation
Duration: 2 years
Scale of Implementation: 1 site
High priority sites: Bargatton Loch, Scotland
Comments:
Key Action 3
Proposed Action: Trial reintroduction to Esthwaite Water assuming that ex situ cultivation is successful.
Action targets: 6. Recovery solutions trialled
Action type: (Re-)introduction
Duration: 3-5 years
Scale of Implementation: Unknown
High priority sites: Esthwaite water
Comments:
Acknowledgment:
Data used on this website are adapted from Threatened species recovery actions 2025 baseline (JP065): Technical report and spreadsheet user guide (Natural England, 2025). Available here.