How to Grow
Verbena bonariensis from Seed
The see-through purple veil — Short-Lived Perennial H4; RHS AGM; RHS Pollinators; tiny lilac-purple flowers on wiry 1.5m stems July–first frost; the single best UK plant for butterfly attraction; "see-through" airy quality — plant at front of border without obscuring anything behind; prolific self-seeder (leave stems over winter; cut to ground in spring); surface sow Jan–Apr at 18–21°C (light required; erratic; cold stratify in fridge 2 weeks if slow)
Verbena bonariensis is one of the most distinctive and ecologically valuable plants available to UK gardeners: a 1.5m perennial that despite its height can be planted at the very front of a border because its wiry, branching stems are so sparse and transparent that they create a floating "purple veil" of tiny lilac-purple flowers without blocking the view of anything behind them. The RHS Award of Garden Merit and the RHS Plants for Pollinators listing both reflect qualities that garden designers and wildlife gardeners have independently recognised for decades: this is a plant of outstanding ornamental beauty that is simultaneously one of the most important butterfly plants in the British garden.
Its short-lived perennial nature — individual plants may not survive the harshest UK winters — is effectively irrelevant in practice, because Verbena bonariensis self-seeds so prolifically that a colony established in a garden is nearly impossible to lose. Leave the stems standing over winter for insects and birds; cut to ground in spring when new growth appears; and the dozens of self-sown seedlings that appear each spring ensure a permanent, self-renewing presence that requires minimal deliberate management. The only significant challenge in growing Verbena bonariensis is the erratic germination of the seeds, remedied simply by cold stratification in the refrigerator if seedlings fail to appear after four weeks of warmth.
Quick Facts at a Glance
Plant Type
Short-Lived Perennial H4 — RHS AGM; RHS Pollinators; self-seeds prolifically to replace itself
Flowers
Tiny lilac-purple flowers in flat-topped clusters on stiff square stems; July to first frost
Height
To 1.5m on strong, wiry, self-supporting stems; "see-through" airy quality
Butterflies
Widely regarded as the single best UK plant for attracting butterflies; Red Admirals, Peacocks, Painted Ladies
Self-seeding
Leave stems over winter; cut to ground in spring; dozens of seedlings replace parent plants naturally
Difficulty
2 out of 5 — erratic germination is the main challenge; once established, largely self-sufficient
Understanding Verbena bonariensis
The See-Through Plant — Architecture Without Obstruction
Verbena bonariensis has a quality unique among tall garden plants: its stems are so wiry and sparse that despite reaching 1.5m in height, it can be planted at the very front of a border without blocking the view of anything behind it. The stiff, square, branching stems carry clusters of tiny lilac-purple flowers at their tips, creating what is often described as a "purple veil" — a haze of colour that floats above and through the surrounding planting rather than forming a solid screen. This transparency means it works simultaneously as a vertical element, a colour layer, and a see-through structural plant in positions where a solid 1.5m plant would be entirely inappropriate.
Self-Seeding Perennial — Near-Permanent Without Replanting
Verbena bonariensis is technically a short-lived perennial — individual plants may not survive a harsh UK winter — but its prolific self-seeding behaviour effectively makes it permanent in any garden where it is allowed to set seed. Leave the stems standing over winter (the hollow stems provide shelter for overwintering insects and the seedheads feed birds); cut back to ground level in early spring when new green growth appears at the base; and dozens of seedlings will self-sow nearby to naturally replace any parent plants lost to winter cold. In practice, a established colony of Verbena bonariensis is nearly impossible to lose entirely.
Erratic Germination — Cold Stratification Trick
Verbena bonariensis seeds require light for germination — surface sow without covering. Maintain at 18–21°C. Germination is typically erratic, taking anywhere from 14 to 28 days. If no seedlings appear after four weeks, place the seed tray in a refrigerator for two weeks (cold stratification), then return to warmth — this temperature change often breaks dormancy and triggers germination in otherwise reluctant seeds.
Sowing & Growing On
Surface Sow Jan–Apr at 18–21°C — Light Required — 14–28 Days (Erratic) — Cold Stratify if Slow — Plant May–Jun — Full Sun — Free-Draining Soil — Leave Stems Over Winter
Surface sow Jan–Apr at 18–21°C (light required; 14–28 days; erratic). If slow after 4 weeks, cold stratify in fridge 2 weeks then return to warmth. Plant May–Jun at 45–50cm spacing. Full sun; free-draining. Leave stems over winter; cut to ground in spring.
-
Surface sow January–April on moist seed compost at 18–21°C — do not cover. Light is required for germination. Press gently to ensure seed-to-compost contact. Germination is erratic: 14–28 days is normal. If no seedlings appear after four weeks, place the tray in a refrigerator for two weeks, then return to warmth at 18–21°C — cold stratification often breaks dormancy.
-
Prick out into individual 7.5cm pots when seedlings have 2–3 true leaves; grow on in good light. Harden off over 7–10 days before planting out. Plant in late May or June at 45–50cm spacing once all frost risk has passed. Verbena bonariensis is fully capable of supporting itself — staking is not required despite the 1.5m height.
-
Plant in full sun with excellent drainage; water in well and leave largely to its own devices. Once established, Verbena bonariensis is highly drought-tolerant and requires minimal ongoing care. Feed with a balanced fertiliser in spring of established plants. Avoid over-rich soil, which promotes lush leafy growth at the expense of the prolific flower production.
-
Leave all stems standing over winter; cut to ground in early spring when new growth appears at the base. The hollow stems shelter overwintering insects; the seedheads provide winter bird food; and the structural dead stems add garden interest through the winter months. Cut back only when green growth is visible at the base in spring — cutting back in autumn risks cold damage to the crown.
Growing On & Care
The Butterfly Plant
Verbena bonariensis is consistently cited by wildlife gardeners and entomologists as one of the best — many would argue the single best — flowering plant in the UK garden for attracting butterflies. The flat-topped flower clusters provide the stable landing platforms that larger butterflies (Red Admirals, Peacocks, Painted Ladies) need to perch and feed, while the accessible tubular florets supply abundant nectar from July through to the first frosts. The long flowering season — extending further into autumn than most butterfly-attractive plants — makes Verbena bonariensis particularly valuable at a period when nectar sources are declining and migrating species are building their energy reserves.
RHS Award of Garden Merit
Verbena bonariensis holds the RHS Award of Garden Merit for its outstanding ornamental and wildlife value in UK garden conditions. The RHS Plants for Pollinators listing confirms its ecological value independently. Used extensively by garden designers in award-winning show gardens at Chelsea and Hampton Court — most famously in the prairie-style planting schemes of Piet Oudolf — it has become one of the defining plants of contemporary naturalistic garden design while remaining entirely at home in a traditional Norfolk cottage garden.
See-Through Design Quality
The specific design value of Verbena bonariensis — the quality that makes it appear in virtually every contemporary planting scheme — is its "see-through" transparency. Planted at the front of a border, it creates a layer of floating purple colour without blocking the view of any plant behind it. Planted in the middle, its stems weave through surrounding plants in a way that no solid shrub or tall perennial can replicate. It works particularly well with ornamental grasses (the purple and the buff or silver complement each other), with Rudbeckia (purple and gold), and with roses (the airy purple softens the structure of the rose without competing with the flowers).
As a Cut Flower
The branching stems of Verbena bonariensis cut well when taken at the stage where the outer ring of the flower cluster is open. Vase life 7–10 days. The airy, branching quality of the stems provides natural movement and structure in a vase without the heaviness of solid-flowered stems. Use it as a filler in cottage-style mixed summer arrangements — the purple coordinates with almost every other colour and the light, floating stems provide contrast to the heavier flower forms of roses, dahlias, and sunflowers.
From Buenos Aires
Verbena bonariensis is native to South America — to Argentina and Brazil — and its specific name (bonariensis) refers to Buenos Aires, from where early specimens were collected. It was first grown in England in 1726 by the Sherard brothers. The name means "of Buenos Aires." Despite its South American origins, it has naturalised across much of southern England and is sufficiently hardy (H4) to survive most UK winters, particularly in free-draining soil where the roots are never waterlogged.
Self-Seeding Management
In a garden where Verbena bonariensis is thriving, self-seeding can be prolific — dozens of seedlings appearing in spring around and beyond the parent plants. Young seedlings are easy to identify (slender, with the characteristic rough-textured lance-shaped leaves) and easy to transplant when small. Thin ruthlessly to 45–50cm spacing; pot up surplus seedlings to give to other gardeners; or hoe out unwanted seedlings in spring before they establish. The self-seeding habit is an asset in the naturalistic or cottage garden but requires management in a formal scheme.
Growing Calendar
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sow indoors (Jan–Apr; surface; 18–21°C; light req.) |
|
|
|
|
||||||||
| Plant out (May–Jun; full sun; free-draining; 45cm) |
|
|
||||||||||
| Purple veil in flower (Jul–Oct; butterfly magnet) |
|
|
|
|
||||||||
| Leave stems (Nov–Mar; wildlife shelter; self-seeds) |
|
|
|
|
|
Common Problems & Solutions
| Problem | Likely Cause | What to Do |
|---|---|---|
| No germination after 4 weeks | Seeds need cold stratification to break dormancy | Place the seed tray in a refrigerator for 2 weeks, then return to warmth at 18–21°C. This temperature change breaks dormancy in otherwise reluctant seeds. |
| Plants dying in winter | Short-lived perennial — normal; also waterlogged roots | Allow self-seeding before cutting back: leave stems over winter. In free-draining soil plants survive more reliably. The colony renews itself from seedlings even when parent plants die. |
| Powdery mildew on leaves | Late-season; dry conditions at root while humid overhead | Water at the base. Good air circulation. Late-season mildew is cosmetically unpleasant but rarely fatal to established plants. |
| Seedlings everywhere; invasive spreading | Prolific self-seeder — normal and manageable | Thin or transplant seedlings in spring when small. Hoe out unwanted seedlings before they establish. Accept the self-seeding habit as a feature rather than a problem. |
Plant Specifications
The floating purple veil that needs no staking, self-seeds freely, and brings more butterflies to the garden than almost any other plant
Surface sow January–April on moist compost at 18–21°C (no cover; light required; 14–28 days; erratic). If no seedlings after 4 weeks, place tray in fridge for 2 weeks then return to warmth. Plant May–June at 45cm in full sun with free-draining soil. No staking needed. Leave stems over winter for wildlife; cut to ground in spring when new growth appears. Self-seeds prolifically.
Shop Verbena bonariensis Seeds →