In Cornwall’s spring, the Green Hairstreak butterfly gleams against golden gorse. This small, elusive species depends on both gorse and bird’s-foot trefoil for survival, making the protection of scrub mosaics and grassy slopes vital to its future.
Emerald on Gold: The Green Hairstreak and Cornwall’s Spring Gorse
By mid-spring, Cornwall’s cliffs and heathlands are awash with gold. The gorse (Ulex europaeus) is in full bloom, its coconut-scented flowers catching the sun and drawing in a wealth of life. Among the bees and small day-flying moths is one of Cornwall’s most easily overlooked butterflies: the Green Hairstreak (Callophrys rubi).
With a wingspan of just 27–34 millimetres, the Green Hairstreak is Britain’s only green butterfly. At rest, it always closes its wings, hiding the brown upperside and revealing an iridescent green underside marked by a fine, sometimes broken, white streak. In the right light, these wings shimmer like malachite against the gorse’s gold.
A Local but Widespread Resident
In Cornwall, the Green Hairstreak is locally distributed but widespread, especially along the coasts and in upland heath. It is most often seen from April into May, when males establish territories and the species is most active, although in warm springs the first individuals can appear as early as late March.
Small colonies are typical. Each is tightly tied to its patch of suitable habitat—a sunny, sheltered slope with a mix of flowering gorse and other nectar plants, patches of bare ground for basking, and structural variation from low turf to taller scrub. In coastal areas, these habitats may include old Cornish hedges, cliff-top heath, bracken edges, and even disused quarries.
The Green–Gold Partnership
For the Green Hairstreak, gorse is more than a backdrop—it is the centrepiece of its spring life cycle.
Nectar source: Ulex europaeus blooms for much of the year, with occasional flowers appearing in late winter. On Cornwall’s warmest coastal slopes, these early blooms can sustain the first males and pre-peak females before the main April–May flush, extending gorse’s value to the butterfly’s season.
Territory: Males perch on the tips of flowering gorse or heather, intercepting rivals in short, spiralling flights. These aerial tussles are most frequent in full sun when territorial boundaries are strongly defended.
Larval foodplant: In coastal sites, gorse is the main larval host, with eggs laid singly on buds and fresh shoots. Inland—particularly on calcareous or grassy slopes such as parts of Bodmin Moor and the Carnmenellis uplands—bird’s-foot trefoil (Lotus corniculatus) is not just a secondary option but a primary larval foodplant, equally important to colony success.
This synchrony of emergence, peak flowering, and larval development is the result of long adaptation to Cornwall’s coastal and upland rhythms.
Beyond Gorse
Green Hairstreak caterpillars also use broom, bramble, and bilberry in some habitats, while adults will nectar from a variety of spring blooms including heather, bramble flowers, and hawthorn. This flexibility helps the butterfly cope with seasonal shifts or localised gorse loss.
Heathland Habitats in Detail
The Green Hairstreak’s preferred Cornish habitats share common features:
Open, sunny structure: South- and west-facing slopes maximise warmth and shelter.
Scrub mosaic: A mix of gorse, heather, broom, and bracken creates variety in height and structure.
Bare ground patches: These act as warm basking spots and movement corridors for adults.
Wind shelter: Low banks, Cornish hedges, and thickets of gorse or bracken protect butterflies from strong Atlantic winds.
Plant diversity: A combination of gorse, bird’s-foot trefoil, and other larval plants ensures colonies can cope with seasonal variability.
Connectivity between habitat patches is critical—colonies survive best when they can move between neighbouring heaths, slopes, or field edges.
Cornwall’s Climate Advantage—and Risk
Cornwall’s mild, oceanic climate means Green Hairstreaks can take advantage of early warmth in late March or April, making them one of the first butterflies seen on the coast each year. South-facing cliffs and heathland slopes can warm quickly, offering long feeding and basking windows.
However, the species’ reliance on synchrony with gorse flowering makes it vulnerable to climate shifts. A warm March could bring butterflies out before the main gorse peak, while cold, wet Aprils can delay both butterfly emergence and flowering. More frequent spring droughts may shorten the window of fresh growth for caterpillars, while intense storms can strip flowers from exposed sites.
Warmer springs could, in theory, extend the flight season slightly, but such changes will not help if larval foodplants and climate cues fall out of sync.
Why Small Colonies Matter
Green Hairstreaks rarely form large, continuous populations in Cornwall. Instead, their persistence depends on many small colonies scattered across the landscape. Each acts as a genetic and ecological “insurance policy” for the others—if one is lost to habitat clearance or extreme weather, neighbouring colonies can recolonise.
This structure also reflects their tight link to microclimates: a sheltered gorse bank may thrive while a more exposed slope suffers from spring gales or salt-burn. Conservation here is hyper-local—protecting a few hundred square metres of gorse and associated scrub can safeguard an entire colony.
Conservation Priorities
To maintain Cornwall’s Green Hairstreaks, management must keep the habitat mosaic intact:
Avoid gorse clearance between March and June, when adults are feeding and eggs are being laid.
Use rotational cutting or light grazing to maintain a mix of mature flowering gorse and younger regrowth.
Retain sunny, sheltered slopes and hedge banks.
Encourage connectivity between habitat patches with gorse-rich field margins, Cornish hedges, and heathland corridors.
Even small-scale management—such as maintaining gorse on a single hedge bank—can help sustain local colonies.
A Mid-Spring Encounter
It is a bright April morning on the Lizard Peninsula. The air is filled with the warm scent of gorse and the distant crash of waves. On a sunlit sprig, a flicker of green catches the eye—a Green Hairstreak, wings closed, perfectly matched to the shadows of the bloom. For a moment it sits motionless, then darts upward to intercept another, the two spiralling together in a quick aerial dance before returning to their golden stage.
How to Spot and Where to See the Green Hairstreak in Cornwall
When to Look
Main flight period: Mid-April to late May is peak activity.
Early sightings: In warm springs, adults can emerge in late March on sheltered coastal slopes.
Late records: Occasionally into early June at higher altitudes or in cooler inland sites.
How to Spot Them
Size: Very small (wingspan 27–34 mm).
Colour: Always perched with wings closed, showing a shimmering green underside with a fine white streak (often broken).
Behaviour:
Males perch on gorse or heather tips, darting out to intercept rivals in short spiral flights.
Females fly lower, investigating fresh gorse shoots or bird’s-foot trefoil for egg-laying.
Adults often bask on bare ground or low vegetation in full sun.
Best weather: Warm, sunny, and still conditions. Avoid windy or overcast days when they stay hidden in scrub.
Where to Look in Cornwall
Coastal Hotspots
The Lizard Peninsula – gorse-rich heathland and cliff tops, especially around Kynance and Predannack.
West Penwith – Land’s End to Zennor, with sheltered cliff-top gorse banks.
North Cornwall Cliffs – around Pentire, Stepper Point, and Bude’s downs.
Inland Locations
Bodmin Moor – grassy slopes with bird’s-foot trefoil and scattered gorse.
Carnmenellis Uplands – mosaic of heath and pasture with trefoil patches.
Disused quarries – warm, sheltered microclimates with scrub and wildflowers.
Key Plants to Check
Gorse (Ulex europaeus) – main nectar and larval plant in coastal areas.
Bird’s-foot trefoil (Lotus corniculatus) – primary larval plant in some inland colonies.
Other nectar sources: Heather, bramble flowers, hawthorn blossom.
Phenology tip: In Cornwall’s warmest sites, gorse can flower in late winter, supporting early-emerging adults before the main bloom.
Fieldcraft Tips
Move slowly and scan sunlit gorse tops for the tell-tale green flash.
Use binoculars for close-up observation—Green Hairstreaks rarely allow close approach.
Look for perching points where males return repeatedly after short flights.
On cooler days, check sheltered banks and hedge edges for basking individuals.
Photographing the Green Hairstreak
Early morning or cooler periods keep them still for longer.
Position yourself so the light catches the wing scales for maximum green iridescence.
Include gorse or trefoil flowers in the shot for context.
Conservation Awareness
Stay on paths to avoid damaging gorse and trefoil stands.
Avoid disturbance during peak egg-laying (April–May).
Report sightings to the Cornwall Butterfly Conservation branch to help monitor colony health.
Quick ID Card
Scientific name: Callophrys rubi
Wingspan: 27–34 mm
Underside: Bright green with fine white line
Flight period: Late March–May (peak mid-April–May)
