Introduction

Decumaria sinensis (Chinese Decumaria) is a evergreen climber in the Hydrangeaceae family, reaching 5 metres with cream-green flowers in spring. Hardy in USDA zones 7-9. Valued for its fragrant flowers.

Decumaria sinensis, commonly known as Chinese Decumaria, is a evergreen evergreen climber in the Hydrangeaceae family. The plant reaches 5 metres in height with a spread of approximately 2 metres, climbing by means of aerial rootlets that adhere to surfaces. The cream-green flowers appear in spring, providing seasonal colour. The flowers emit a delightful fragrance that carries well in still air, making this an excellent choice near seating areas and pathways. The foliage is dark_green, maintaining its colour year-round as an evergreen. Growth rate is slow-growing, adding less than 30 cm per year. Native to China, this species has become a valued ornamental plant in temperate and subtropical gardens worldwide.

Botanical Description

Classification: Hydrangeaceae > Decumaria > sinensis. The Hydrangeaceae (hydrangea family) includes both shrubby and climbing species found across Asia and the Americas. This species is native to China and was introduced to European gardens from China. The genus Decumaria contains several species, many of which are valued in horticulture for their climbing habit and ornamental qualities.

Climbing Mechanism

Decumaria sinensis climbs using aerial rootlets that adhere to surfaces. These small, adventitious roots emerge along the stems and secrete a natural adhesive that bonds to rough surfaces such as brick, stone, and bark. This self-clinging mechanism means the plant generally does not require additional support structures on suitable surfaces. The aerial roots can penetrate small cracks and crevices, which may cause cosmetic damage to rendered walls or aging mortar. The plant can reach 5 metres when growing on a suitable vertical surface.

Group Climbing Guide — Climbing Hydrangea

Aerial roots attach to rough surfaces. Slow to establish (2–3 years), then vigorous. Needs no tying.

Planting Guide

Step 1 — Site Selection: Choose a position in partial shade (3-6 hours of filtered or morning sunlight) with well-drained soil. Consider the mature size (5m tall × 2m wide) when selecting the site. Step 2 — Support Installation: Install a wall (with or without wire supports) or solid vertical surface before planting. Ensure the support is rated for the mature weight of the plant. Step 3 — Soil Preparation: Dig a hole twice the width and 1.5 times the depth of the rootball. Mix in well-rotted compost and a slow-release fertilizer. Target pH 5.5-7.0. Step 4 — Planting: Plant at the same depth as the container (except clematis, which should be planted deeper). Water thoroughly and firm in gently. Step 5 — Aftercare: Mulch with 5-8 cm of organic matter. Water regularly during the first growing season. Guide initial stems toward the support using soft ties. Protect from slugs and snails in the early stages.

Climate & Hardiness

Spring: Apply a balanced slow-release fertilizer as new growth begins. Mulch around the base with organic matter. Tie in new stems to supports. Check for winter damage and prune out any dead or damaged growth. Summer: Water regularly , especially during dry spells. Feed monthly with a liquid fertilizer during the growing season. Continue training and tying in new growth. Deadhead if applicable. Autumn: Reduce watering and feeding as growth slows. Apply a thick mulch to protect roots from winter cold. Check for any pest or disease issues before winter. Winter: This species is reliably hardy in most temperate gardens. Check ties and supports. Plan any structural pruning for late winter.

Overwintering Guide

Fully hardy. No protection needed. Old flowerheads provide winter interest — leave until spring.

Propagation

Stem cuttings (primary method): Take semi-ripe cuttings in mid to late summer (July-August). Select healthy, current season's growth, cutting just below a leaf node. Cuttings should be 10-15 cm long. Remove lower leaves, dip the cut end in hormone rooting powder, and insert into a well-drained mix of perlite and peat (50:50). Place in a propagator or cover with a clear plastic bag. Bottom heat of 18-21°C improves success rates. Roots typically develop within 4-8 weeks. Success rate: 60-80%. Layering (alternative): In spring, select a low-growing flexible stem. Wound the underside lightly, pin it to the ground with a wire staple, and cover with soil. Keep moist. Roots develop over 6-12 months. Sever from the parent plant and transplant the following season. Success rate: 80-90%.

Pests & Diseases

Common Problems

Group Disease & Pest Reference (Climbing Hydrangea)

• Leaf spot — occasional brown spots in wet weather; usually minor and cosmetic
• Scale insects — on old woody stems; scrape off or treat with winter oil wash
• Powdery mildew — rare but possible in extreme drought; water at base during dry spells
• Honey fungus — can affect established plants; maintain plant vigour
• Vine weevil — notch-shaped leaf damage; search for and destroy grubs in soil around base

Training & Pruning

Pruning timing: Prune after flowering or in early spring. Formative pruning: In the first 2-3 years, focus on building a strong framework of main stems by selecting well-placed shoots and tying them to the support. Remove weak, crossing, or badly-placed stems. Maintenance pruning: Once established, shorten side shoots after flowering to maintain shape and encourage new flowering wood. Remove any dead or damaged growth promptly. Thin overcrowded stems to maintain good air circulation. Training: Tie in new growth regularly throughout the growing season using soft garden twine or plant clips. Spread stems evenly across the support for the best coverage and flowering display. Self-clinging species need minimal tying once established.

Pruning Guide — Climbing Hydrangea

Minimal pruning needed. After flowering, trim outward-growing shoots to maintain shape. Remove dead wood spring.

Support Structures

Decumaria sinensis is a self-clinging climber that generally does not require additional support structures on suitable surfaces. However, young plants may need initial guidance: Suitable surfaces: Brick, stone, rough-rendered walls, mature tree trunks. The plant adheres best to rough, porous surfaces. Temporary support: Use small nails or adhesive hooks to guide young growth until the plant's own attachment mechanism takes hold (usually within one growing season). Weight considerations: Mature plants can be extremely heavy. Ensure the wall or structure is sound before allowing extensive growth. A mature specimen covering a large wall area can weigh hundreds of kilograms when wet. Dimensions: Allow for a mature height of 5m and spread of 2m.

Support Guide — Climbing Hydrangea

Self-clinging: walls, fences, tree trunks. No support needed once established. North-facing walls fine.

Wildlife Value

Decumaria sinensis is a valuable pollinator plant, attracting bees, butterflies, and hover flies to the garden. The fragrant flowers are particularly attractive to night-flying moths. Ecosystem services: The climbing habit creates valuable vertical habitat, providing shelter and nesting opportunities for birds and invertebrates. Dense foliage offers roosting sites for birds and overwintering habitat for beneficial insects.

Landscape Design

Walls and fences: Decumaria sinensis is well-suited to covering walls and fences, providing year-round screening. Self-clinging habit means no additional wiring is needed on rough surfaces. Pergolas and arbors: Excellent choice for pergolas, creating a dramatic overhead canopy. Screening: Creates year-round screening when grown on appropriate support. Effective for disguising unsightly structures, dividing garden rooms, or creating private spaces. Feature plant: Makes a stunning focal point when grown on a prominent support structure. Combine with other climbers for a layered, naturalistic effect.

History & Culture

Decumaria sinensis has been cultivated in gardens since its introduction from China. Originally from China, it has become valued in horticulture for its fragrant flowers and ornamental qualities. The genus Decumaria has contributed significantly to the diversity of climbing plants available to gardeners, with species found across multiple continents and climate zones.

Container Growing

Decumaria sinensis is not recommended for container growing due to its vigorous root system and large mature size (5m). The plant requires open ground to develop a sufficiently large root system for healthy growth and flowering. If space is limited, consider a more compact cultivar or alternative species better suited to container culture.

Frequently Asked Questions

Seasonal Care Calendar