Signature Plants of Cornwall: What Defines Our Gardens and How to Protect Them

There are plants that belong to Cornwall in a way that goes beyond horticulture. They are part of the visual language of the county — as much a part of its identity as the granite coastline, the light off the sea, or the smell of gorse on a warm spring day. Encounter them in gardens, along roadsides, spilling over walls in St Ives or Falmouth or Penzance, and something registers that is deeper than simple aesthetic pleasure. These plants say: you are in Cornwall.

Understanding which plants carry that weight — and why — is not merely an exercise in botanical sentiment. It is fundamental to making good decisions about how Cornish gardens are planted, managed, and developed into a future of climate change. Because several of these defining plants are under genuine pressure, and their gradual disappearance from the Cornish landscape would represent a loss that no amount of fashionable new planting could fully replace.

What makes a plant a signature species

The term signature species, as I use it in the context of Cornish gardens, describes those plants that most powerfully define the character and atmosphere of a place. They are the species without which a garden — or a landscape — would feel fundamentally different. Not just less beautiful, but less itself.

Signature species earn that status through a combination of factors. Visual distinctiveness — a form or silhouette that is immediately recognisable and strongly associated with a particular place. Historical presence — plants that have been part of the landscape long enough to become embedded in collective memory and cultural identity. Ecological significance — species that support other organisms and contribute to the functioning of the garden as a living system. And emotional resonance — the capacity to evoke a sense of place through association, memory, and repeated encounter.

In Cornwall's public gardens, signature species are often the plants around which the entire character of the garden is organised. Hydrangeas and Rhododendrons in the great valley gardens. Palms and tree ferns in the more contemporary subtropical spaces. Prunus 'Accolade' and cinerarias at the Barbara Hepworth Sculpture Garden, where I work as head gardener, and where maintaining these plants is not simply a horticultural decision but a responsibility to the artistic and historical integrity of the place, as I explore in my article on the preservation versus adaptation dilemma facing Cornwall's historic gardens.

The plants that define Cornwall at a county level

Beyond individual gardens, Cornwall has signature plants at the scale of the wider landscape — species so characteristic of the county's coastal communities and garden culture that they contribute to a shared sense of what Cornwall looks and feels like.

Cordyline australis is perhaps the most immediately recognisable. Its bold, architectural form — the fountain of long, strap-like leaves rising from a bare trunk — has become almost synonymous with the Cornish Riviera. It lines garden paths, rises above boundary walls, and punctuates the rooflines of coastal towns from St Ives to Falmouth. Originally from New Zealand, it has been grown in Cornwall for long enough to feel entirely at home, and its presence signals the mild, maritime climate of the far southwest in a way that no other plant quite matches.

Trachycarpus fortunei, the Chusan palm, performs a similar role — its distinctive silhouette immediately evoking the Mediterranean-influenced warmth of Cornwall's coastal gardens. Agapanthus, flowering in shades of blue and white through late summer, is another defining presence — lining the paths of countless Cornish gardens and spilling cheerfully onto pavements in the warmest coastal spots. And the great flowering shrubs that characterise Cornwall's valley gardens — Rhododendron, Camellia, Magnolia — represent a signature at the scale of the county's most celebrated horticultural landscapes.

These plants did not come to define Cornwall by accident. They are here because the maritime climate made them possible — because Cornwall's mild winters and reliable moisture created conditions in which species that would struggle elsewhere could thrive with ease. That is precisely why the changing climate poses such a particular challenge to Cornish garden identity. The conditions that made these plants possible are themselves changing.

The threats they face

Several of Cornwall's most characteristic plants are under pressure simultaneously, from a combination of climate-related stress and specific pests and diseases.

Cordyline australis has been dying across Cornwall in significant numbers. The primary culprits are cordyline slime flux — a bacterial infection that causes the growing point to rot — and the increasing frequency of cold, wet winter periods that, while mild by national standards, can be damaging to a species that evolved in the relatively dry winters of New Zealand. Walk through any Cornish coastal town and the gaps are visible — spaces where mature specimens once stood, sometimes replaced with younger plants, sometimes simply left empty.

Agapanthus faces a growing and specific threat from agapanthus gall midge, Enigmadiplosis agapanthi, a relatively recently arrived pest whose larvae feed within the developing flower buds, causing distortion and failure. As the climate warms and the pest's range extends, the pressure on agapanthus plantings across Cornwall is likely to increase. Vigilance, early detection, and the removal and destruction of affected growth are currently the most effective responses, but the threat is real and ongoing.

The great Rhododendrons and woodland shrubs of Cornwall's valley gardens face pressure from Phytophthora ramorum, a devastating water mould that spreads readily in warm, wet conditions. Cornwall has already seen serious outbreaks — at Trengwainton, where infected Rhododendron ponticum in adjacent woodland spread disease into the garden with severe consequences. Warmer, wetter winters create precisely the conditions that favour phytophthora's spread, and the risk to Cornwall's most treasured garden collections is significant. I discuss the broader pest and disease implications of climate change in my article on pests, diseases and climate change in Cornish gardens.

Hydrangeas — the backbone of many of Cornwall's historic garden displays — have been suffering visibly in recent dry springs and summers, wilting in ways that would have been unusual a decade ago. As I describe in my article on how climate change is already affecting Cornish gardens, this is part of a broader pattern of drought stress affecting plants that were once considered entirely reliable in Cornwall's generous climate.

How to protect what matters most

The response to pressure on signature species is not to give up on them. It is to direct resources towards their care deliberately and intelligently, for as long as it remains feasible to do so — because the aesthetic and cultural value they provide is not easily replaced.

For Cordyline australis, good drainage is the most important preventive measure — the combination of cold and waterlogging is more damaging than cold alone, and improving drainage around established specimens can significantly reduce their vulnerability. Monitoring for early signs of slime flux, removing affected growth promptly, and avoiding wetting the growing point during watering all help to reduce risk. Younger plants grown from seed or cuttings of known provenance may prove more resilient than older specimens, and maintaining a succession of younger plants alongside mature ones is a sensible long-term strategy.

For Agapanthus, monitoring flower buds carefully from late spring onwards for signs of gall midge damage, and removing and destroying affected material immediately, is currently the most effective approach. Choosing robust, well-established clumps rather than weak divisions, and ensuring plants are grown in conditions that suit them — good drainage, full sun, reasonable fertility — gives them the best chance of tolerating pest pressure.

For Rhododendrons and other plants vulnerable to Phytophthora, biosecurity is paramount. Avoiding movement of potentially infected soil or plant material, monitoring for symptoms, and maintaining good air circulation around vulnerable plants all reduce risk. The broader question of which species to prioritise for long-term retention — and which to begin transitioning away from — is one that every manager of a significant Cornish garden collection needs to address proactively rather than reactively.

The water management strategies I describe in my article on water-smart gardening in Cornwall are directly relevant to the care of signature species under drought stress — irrigation infrastructure, rainwater harvesting, and mulching can all help to maintain the health of plants that are increasingly challenged by dry summers.

When replacement becomes necessary

There will come a point, for some signature species in some gardens, when the cost — in resources, management time, and repeated disappointment — of maintaining plants in conditions they are no longer suited to outweighs the benefit. When that point arrives, the choice of replacement matters enormously.

The right approach is not to default to whatever is most readily available, but to find species that perform genuinely similar aesthetic and ecological roles — that carry something of the same visual weight, seasonal interest, and character — while being better suited to the conditions ahead. This is demanding, but it is the approach most likely to preserve the essential quality of a garden through the transition. The plant selection principles I set out in my article on how to choose plants that will thrive in a Cornish garden provide a framework for making those choices well.

For holiday home gardens where the distinctly Cornish character of the planting is part of what guests come to experience, maintaining signature species — or finding well-chosen replacements when necessary — is not simply an aesthetic consideration but a practical one. And for commercial properties across the county, the plants that define the Cornish landscape are also part of the brand of place that makes Cornwall such a compelling destination.

A responsibility worth taking seriously

The signature plants of Cornwall are part of a shared heritage — not owned by any individual garden or property owner, but collectively maintained across thousands of private and public spaces throughout the county. Their gradual erosion, if it is allowed to happen without a concerted effort to understand and address the causes, would represent a real and lasting loss to the landscape and identity of Cornwall.

Taking that responsibility seriously — through informed care, proactive management, and thoughtful replacement when necessary — is one of the most meaningful contributions that any Cornish gardener, garden owner, or property manager can make to the place they inhabit.

Jodi Dickinson MHort(RHS) is a professional horticulturist and head gardener at the Barbara Hepworth Museum and Sculpture Garden, St Ives. Juniper Gardens provides specialist garden maintenance, garden design and ecological garden care across mid and west Cornwall. View Jodi's full profile here.