How to Grow Clematis Jackmanii

Clematis Jackmanii

Clematis × jackmanii

vine

Clematis Jackmanii is a deciduous woody vine known for its spectacular large, deep purple flowers that bloom profusely from mid-summer through fall. This hybrid clematis is one of the most popular and reliable varieties, making it an excellent choice for trellises, arbors, and pergolas. It grows vigorously and can reach 8-10 feet in height when well-established.

Growing Conditions

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Sun: Full sun, 6+ hours daily; afternoon shade beneficial in hot climates (zones 8-9)

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Water: Moderate and consistent moisture; water deeply 1-2 times per week during growing season. Keep soil moist but not waterlogged. Mulch heavily to keep roots cool and maintain moisture.

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Spacing: 36 inches

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Days to maturity: Established flowering occurs in year 2-3 from transplant

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Planting depth: Plant 2-3 inches deeper than container to promote basal shoots; bury stem sections to encourage new growth if vine is damaged

Soil

Type: Well-draining loamy soil, slightly alkaline to neutral preferred

pH: 6.5-7.5

Amendments:

Lime to raise pH if naturally acidic Organic compost or aged manure Perlite or coarse sand for drainage

Growing Zones

Find your zone →

Thrives in zones 4-9; performs best in zones 5-8 with moderate summers

4a 4b 5a 5b 6a 6b 7a 7b 8a 8b 9a

Growth Stages

Establishment

4-12 months

Young vine with sparse leafy growth; little or no flowering in first year

Water consistently, provide sturdy support structure, mulch base well, protect from wind. Pinch back growing tips to encourage bushiness.

Vegetative Growth

Spring through early summer

Vigorous stem and leaf development with intertwining vines; vine becomes fuller and more established

Guide vines onto support structure, remove dead or weak growth, continue consistent watering. Apply balanced fertilizer monthly during growing season.

Flowering

June/July through September/October

Large (4-5 inch) deep purple flowers with prominent dark stamens appear abundantly along the entire vine

Do not deadhead spent flowers excessively; allow some to set seed for continuous blooming. Water during dry spells. Light feeding with lower nitrogen fertilizer can encourage more blooms.

Summer Dormancy

July-August in zones 8-9

In very hot climates, vines may slow growth during peak heat; foliage remains but flowering may pause temporarily

Increase mulch depth and afternoon shading; maintain consistent soil moisture. Resume normal feeding when cooler weather returns.

Winter Dormancy

November through March

Deciduous vine loses leaves; stems remain visible and dormant. This is a late-flowering type (pruned hard annually).

Prune hard in late winter (Feb-March in most zones) to within 12-18 inches of ground. Remove all tangled and dead wood. This hard pruning rejuvenates the plant and ensures flower production on new growth.

Companion Planting

Plan your garden →

Plant with:

Roses Lavender Russian sage Catmint Clematis (other varieties for succession blooming) Hydrangea Weigela Butterfly bush

Avoid planting near:

Black walnut (produces toxic juglone) Shallow-rooted trees competing for moisture Large shrubs that create heavy shade and poor air circulation

Common Pests

Prune affected stems 12 inches below wilted tissue; improve air circulation; mulch base to prevent soil-borne spore splash; apply sulfur fungicide preventively in spring
Spray foliage with strong water stream; use neem oil or insecticidal soap; ensure adequate humidity and air circulation
Improve air circulation; avoid wetting foliage; apply sulfur dust or baking soda spray; remove heavily affected growth
and
Hand-pick early morning; apply copper tape barriers; use slug traps with beer; encourage beneficial predators like ground beetles
Spray with water; use insecticidal soap; encourage beneficial insects like ladybugs and lacewings; apply neem oil as needed

Uses

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Not for consumption

Culinary

Clematis is not edible and contains potentially toxic compounds. It is grown purely for ornamental purposes, not culinary use. [source]

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Ornamental screening and vertical garden design

Household

Clematis Jackmanii is widely used to cover arbors, pergolas, fences, and trellises, providing dramatic vertical interest and seasonal color to landscapes. Its vigorous growth quickly conceals unsightly structures while adding elegance. [source]

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Pollinator and insect support

Wildlife

The abundant flowers attract bees, butterflies, and other pollinators during peak bloom season. Seed heads provide food and shelter for birds through winter. [source]

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Cut flower arrangements and floral design

Craft

The large, striking purple flowers are prized by florists and garden designers for fresh arrangements and can last 5-7 days in water. The vine's natural curving stems add architectural interest to mixed bouquets. [source]

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Traditional herbal use (historical)

Medicinal

Historically, some clematis species were used in folk medicine, though modern use is not recommended due to toxicity concerns. Contemporary herbalism does not recommend internal or external application. [source]

This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.

Harvest Tips

Not typically harvested, but enjoy cut flowers by cutting stems with blooms in morning when flowers are fresh. Leave flowers on vine for extended garden display through fall. Collect seed heads in autumn if desired for propagation.

Fun Facts

🌱 Clematis Jackmanii was first bred in the 1860s by English nurseryman George Jackman, and it remains one of the most widely grown clematis varieties worldwide over 150 years later.
🌱 The name 'Jackmanii' honors its breeder, and the hybrid is classified as a Group 3 clematis because it blooms on new wood and benefits from hard pruning each winter—a trait that keeps it rejuvenated and flowering year after year.
🌱 Clematis is sometimes called 'the queen of climbing vines' and pairs beautifully with climbing roses in Victorian and cottage garden designs, creating stunning multi-colored vertical displays.

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