Blue trumpet vine (Thunbergia grandiflora)
Thunbergia grandiflora, the Blue trumpet vine, offers showy lavender-blue blooms. An evergreen tropical vine ideal for zones 10-11 or as a fast-growing annual.
Complete Plant Information
Overview
The Thunbergia grandiflora, widely known as the Blue trumpet vine, is a striking, fast-growing tropical climber valued for its abundant, large, trumpet-shaped flowers. This woody-stemmed vine brings dramatic vertical interest to landscapes where temperatures remain mild year-round. Its lush, dark green foliage provides a beautiful backdrop for the signature lavender-blue blooms.
In frost-free climates (USDA Zones 10-11), the Thunbergia grandiflora establishes itself as a robust, evergreen climber, reaching heights up to 30 feet. Even when managed as an annual outside these zones, it can rapidly grow 6-8 feet in a single season, ensuring quick coverage for arbors or trellises. This rapid growth habit and low maintenance make it an excellent choice for gardeners seeking instant tropical impact.
Aesthetically, the Blue trumpet vine is a winner, producing flowers with deep lavender-blue petals and contrasting yellow throats that light up the garden from late summer into early fall. Gardeners appreciate its low maintenance routine, focusing instead on training its twining stems along supportive structures for maximum floral display.
Fast Facts
- Plant Family: Acanthaceae
- Plant Type: Vine
- Native Range: Southeastern tropical Asia
- Hardiness Zones: USDA Zones 10-11
- Size at Maturity:
- Height: 15-30 ft
- Spread: 3-6 ft
- Bloom Time: August to September
- Bloom Description: Lavender blue
- Sun Exposure: Full sun to part shade
- Water Needs: Medium
- Maintenance Level: Low
How to Grow
Optimal planting for Thunbergia grandiflora involves selecting a location that receives full sun or light protection from intense afternoon heat, positioning it near sturdy trellises, arbors, or fences that can support its substantial growth. The soil should be organically rich, fertile, and possess excellent drainage; this vine dislikes sitting in soggy conditions. Where winter hardy (Zones 10-11), planting can occur year-round, but in marginal areas, start the Blue trumpet vine in spring.
Care for this plant is generally straightforward. Provide medium moisture consistently, especially during dry spells or when actively growing. Fertilizing minimally or avoiding heavy feeding promotes better flowering over excessive foliage production. Because it is a vigorous grower, regular attention is required to direct the twining stems where desired, preventing entanglement in unwanted areas.
For gardeners in cooler regions, treat Thunbergia grandiflora as an annual, purchasing new plants each spring. Alternatively, you can initiate growth indoors from seed six to eight weeks before the last expected frost. If you possess a sunny space indoors, container-grown plants or cuttings taken in late summer can be successfully overwintered indoors to start next season’s displays.
Landscape Uses
The dramatic scale of the Blue trumpet vine makes it perfect for dressing up large vertical elements in the landscape. Plant it near sturdy arbors, pergolas, or tall fences to create shaded, flowered passageways or private screens. Where winter protection is needed, large containers are an excellent solution, allowing gardeners to move the handsome Thunbergia grandiflora indoors to a bright sunroom during cold months.
Its vibrant lavender-blue flowers attract attention best when paired with contrasting foliage or annuals. Consider grouping it with plants featuring deep burgundy or bright yellow flowers to enhance the visual pop of the trumpet blooms. When grown as an annual, it excels in hanging baskets, allowing its trailing nature to cascade dramatically over the edges.
When planning the placement of this rapid climber, remember its mature spread of 3 to 6 feet, ensuring it has adequate room to expand without overwhelming smaller nearby shrubs or perennials. Its use as a houseplant also provides a touch of the tropics during the winter months.
Standout Features
Flower Qualities
- Showy
Noteworthy Characteristics
Thunbergia grandiflora, commonly called blue trumpet vine, clock vine, sky vine or sky flower, is a woody-stemmed, evergreen, tropical, twining climber. It grows to 15-30’ long in frost free areas; however, when grown as an annual, it typically reaches 6-8’ long in a single season. The distinctive trumpet-shaped flowers are approximately 3 inches wide, displaying a beautiful lavender blue color accented by yellow throats, appearing singly or in clusters throughout the summer and early fall.
Tolerances
Potential Problems
The Blue trumpet vine generally exhibits few serious troubles with pests or diseases, contributing to its low maintenance profile. However, monitoring is required for common indoor or greenhouse pests if overwintered inside. Inspect foliage regularly for signs of scale insects, spider mites, or whiteflies, particularly during stressful periods or dry indoor winter conditions. Promptly address any infestations using insecticidal soap or horticultural oil to keep your Thunbergia grandiflora healthy.
Frequently Asked Questions
What hardiness zones is Blue trumpet vine suitable for?
Thunbergia grandiflora is winter hardy only in USDA Zones 10 and 11, where it can grow as a perennial vine. In cooler areas, it must be grown as an annual or overwintered indoors.
How large does Blue trumpet vine grow?
When situated in its native tropical environment, the vine can reach heights between 15 and 30 feet with a spread of 3 to 6 feet. As an annual, expect growth around 6 to 8 feet in one season.
When does Blue trumpet vine bloom?
The blooming period for Thunbergia grandiflora is typically from August through September, showcasing its attractive lavender blue flowers.
What sun exposure does Blue trumpet vine need?
This vine performs best when situated in full sun to part shade. Gardeners in very hot climates should ensure the plant receives some light afternoon shade to prevent scorching.
Conclusion
The Thunbergia grandiflora offers exceptional value to gardeners looking for rapid coverage and stunning, uniquely colored blooms. Its vigorous nature as a tropical climber, combined with its low maintenance requirements, ensures a spectacular show throughout the growing season. Before planting, confirm your local USDA hardiness zone compatibility or plan for overwintering your specimen indoors.
Propagation Tips
Taking cuttings is a reliable method for ensuring you have new Thunbergia grandiflora plants next year, especially if you wish to maintain a specific bloom profile or bypass the slower seed-starting process. It is recommended to take semi-hardwood cuttings in late summer specifically for the purpose of overwintering them indoors. Use rooting hormone on the severed end and place the cuttings into a sterile propagation mix, keeping them warm and lightly humid until roots establish.
This method is preferable for gardeners in colder regions compared strictly relying on starting seeds indoors six to eight weeks before spring. Established cuttings often develop into more robust starter plants than seedlings, giving your Blue trumpet vine a head start when moved back outside next season.
Companion Planting
Because the Thunbergia grandiflora requires well-drained, fertile soil and benefits from sun or light afternoon shade, pair it with other tropical or warm-season annuals sharing similar needs. Consider using heat-loving annuals like colorful Mandevilla or trailing Petunias beneath the vine to fill in the base area while the vine climbs its support structure. Avoid companion plants that prefer deep shade or consistently dry conditions, as the needs of the Blue trumpet vine are moderate to slightly rich.
