How to grow clock vine
Overview
Clock vine (Thunbergia grandiflora) is a fast-growing, evergreen tropical climber with large, heart-shaped leaves and showy blue-purple flowers. It is grown to cover fences, pergolas, and trellises, creating lush vertical screens. Growers must provide strong support and regular pruning to keep this vigorous vine in check.
Varieties
- Thunbergia grandiflora 'Alba' — White-flowered form, less common but equally vigorous.
- Thunbergia grandiflora 'Blue Sky' — Large, sky-blue flowers; the most widely sold variety in Australia.
Soil Preparation
Clock vine prefers slightly acidic to neutral soil (pH 6.0–7.0). Enrich with well-rotted manure or compost before planting. Ensure soil is free-draining to avoid root rot; raised beds or mounds help in heavy clay.
Growing Guide
Plant clock vine in a position with bright, filtered light or morning sun and afternoon shade. Use well-draining, loamy soil enriched with compost. Space plants 1–2 m apart along a sturdy trellis or fence. Water deeply twice weekly until established, then reduce to once weekly. Mulch heavily to retain moisture and suppress weeds.
Care
Feed monthly during spring and summer with a balanced liquid fertiliser (e.g., 10-10-10). Prune after flowering to control size and shape; cut back hard in early spring to rejuvenate. Train new shoots onto supports regularly to prevent tangling.
Companion Planting
Pair with other vigorous climbers like bougainvillea or jasmine for a mixed screen. Avoid planting near small, slow-growing shrubs that may be smothered.
Common Pests & Risks
Aphids and whitefly can cluster on new growth; spray with a strong jet of water or use horticultural oil. Scale insects may appear on stems; treat with a systemic insecticide or prune out infested parts. Monitor regularly for early signs.
Troubleshooting
Yellow leaves: overwatering or poor drainage; reduce water and improve soil aeration. Brown leaf edges: low humidity or underwatering; increase misting and water consistency. Stunted growth: insufficient light or cold stress; move to brighter spot and protect from frost. Flowers not appearing: too much shade or high nitrogen; reduce shade and switch to a bloom-boosting fertiliser.