Friday, August 29, 2025

Verbena bonariensis – Complete Grow & Care Guide

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Botanical Name: Verbena bonariensis L.

Synonyms: Verbena patagonica Gillies & Hook. ex Hook.
Family: Verbenaceae
Common names: Purpletop vervain, Tall verbena, Argentinian vervain
Plant type: Short-lived perennial (self-seeds freely)
Height & Spread: 1.2–2 m × 30–45 cm
Habit: Tall, airy, see-through stems with clusters of purple flowers


🌍 Native Range & Habitat


Native to subtropical South America (Brazil, Argentina, Uruguay, Paraguay). Found in grasslands, disturbed ground, and open woodland edges. Prefers full sun and well-drained soils in the wild.


🪴 Planting & Position

  • Light: Full sun is essential for sturdy stems and prolonged flowering.
  • Soil: Moderately fertile, well-drained, pH 6.0–7.5.
  • Spacing: 45–60 cm apart.

🌱 Botanical Description


Erect, quadrangular stems; opposite lanceolate leaves, rough to touch. Terminal, branched inflorescences bearing clusters of small lilac-purple, five-lobed flowers. Fruits are schizocarps with four nutlets.


🌼 Seasonal Interest

  • Flowering period (UK): June–October
  • Wildlife: Attracts bees, butterflies, and hoverflies.
  • Winter: Dried seed heads add structure and feed birds.

💧 Watering

  • Establishment: Keep evenly moist during the first season.
  • Established plants: Drought-tolerant — water only in prolonged dry spells.

🌸 Feeding

  • Low feeding needs — a light application of balanced fertiliser in spring.
  • Overfeeding can cause leggy growth.

✂️ Maintenance & Pruning

  • Leave stems standing over winter for frost protection and habitat.
  • Cut back to ground level in early spring before new shoots appear.
  • Self-seeds readily — deadhead if control is needed.

❄️ Winter Care

  • Hardy to –5 °C; mulch crowns in frost-prone areas.
  • Young plants are less frost-hardy than established clumps.

🐛 Pests & Problems

  • Generally pest-free.
  • Powdery mildew possible in hot, dry, stagnant air — improve ventilation.

🌿 Garden Uses & Companions

Perfect for naturalistic, prairie-style, or wildlife gardens.

  • Companions: Echinacea purpurea, Rudbeckia fulgida, Gaura lindheimeri, ornamental grasses (Miscanthus, Panicum).
  • Excellent cut flower; long vase life.

📅 Quick UK Care Calendar

MonthTask
Feb–MarSow indoors (18–21 °C); germinates in 2–4 weeks
Apr–MayHarden off, plant out after frost
Jun–OctFlowering, water if dry, deadhead if controlling seedlings
Nov–FebLeave stems for winter interest
MarCut back to ground, mulch in cold areas

🌱 Propagation


By Seed (most common)

  • Sowing time (UK): February–March indoors, or April outdoors in mild areas.
  • Method:
    1. Fill trays or modules with fine seed compost.
    2. Sow on the surface — Verbena bonariensis needs light to germinate.
    3. Press gently into the compost but do not cover.
    4. Mist lightly to settle the seeds.
    5. Maintain 18–21 °C; germination takes 14–28 days.
    6. Prick out seedlings into individual pots when large enough to handle.
    7. Harden off before planting out after frost risk has passed.

  • Self-Seeding
  • Plants readily self-sow; seedlings often appear around the parent in spring.
  • Thin or transplant seedlings to prevent overcrowding.
  • To encourage reseeding, leave some flower heads to mature and drop seed in autumn.


By Cuttings (less common but useful for identical clones)

  • In spring, take basal cuttings from new shoots 5–7 cm long.
  • Remove lower leaves, insert into free-draining compost with added grit.
  • Keep in a propagator or under a clear cover at 18–20 °C until rooted.
  • Pot on and grow until ready for planting out.

🏆 Award

  • RHS Award of Garden Merit (AGM) — recognised for reliability and garden performance.

✅ Top Tips for Success

  • Plant in full sun for best flowering and sturdy growth.
  • Let it mingle through borders for a natural, airy look.
  • Leave some seed heads for self-seeding — but be ready to thin seedlings.

Local Gardener
TEL : 07984 112537, info@localgardener.org, 124 City Rd, London EC1V 2NX

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