Clematis

Sun

Full sun to partial shade; afternoon shade helps in hot climates. Flowers best with at least 4-6 hours of direct sun.

Water

Keep the root zone evenly moist but not waterlogged. Water deeply during dry spells, especially in the first two growing seasons and when grown in a container.

Soil

Fertile, moisture-retentive, well-drained soil; neutral to slightly alkaline soil is ideal, but mildly acidic soil is suitable.

Height

8-12 ft (2.4-3.7 m)

Spread

3-6 ft (0.9-1.8 m)

Flowers

Summer into early autumn; large, deep violet-purple flowers with pale cream anthers, produced on the current season's growth.

Foliage

Deciduous green leaves, usually divided into three or more leaflets; climbing leaf stalks curl around supports.

Growth

Fast once established; young plants may take a few seasons to develop strong growth.

Care needed

Medium

• Plant with the crown about 2-3 in (5-8 cm) below the soil surface, avoiding poorly drained sites.
• Provide trellis, wires or mesh with slender sections that the leaf stalks can grip; tie in new shoots loosely.
• Water deeply during dry weather rather than giving frequent light sprinklings.
• Apply a balanced fertiliser in spring at the label rate.
• Mulch annually with compost or well-rotted organic matter, keeping it away from the stems.

Pruning. Pruning group 3: in late winter or early spring, cut all stems back to a pair of strong buds about 12-18 in (30-45 cm) above ground. Remove dead growth and guide the new shoots onto their support.

Late winter

Prune hard before strong new growth starts, leaving healthy buds low on each stem.

Spring

Apply balanced fertiliser and refresh the organic mulch.

Late spring

Tie young shoots loosely to supports before they become tangled or wind-damaged.

Summer

Check soil moisture regularly and water deeply during dry spells.

Late summer

Remove spent flowers if you prefer a tidier display; leave some for their silky seedheads.

Autumn

Clear fallen diseased leaves and check that the support is secure before winter.

• Train over an arch or pergola for a summer display above a path or seating area.
• Grow through a sturdy shrub rose to combine purple flowers with pink, white or pale yellow blooms.
• Use on a narrow trellis against a fence to add height to a small border.
• Grow in a large, deep container with a firm obelisk where border space is limited.

Garden styles it suits: English country, Cottage garden, Romantic rose garden, Traditional, Secret garden and Small-space.

Plant it with: Shrub roses, Hardy geraniums, Lady's mantle, Catmint, Foxgloves and Hostas.

Wildlife: Flowers can provide pollen for visiting insects, although this large-flowered hybrid is less useful to wildlife than many small-flowered clematis. Dense growth can provide shelter for small garden animals.

• Clematis wilt: sudden collapse of individual shoots can occur. Cut affected stems back to healthy tissue, or to ground level if necessary, remove diseased debris and keep watering; healthy roots may send up new shoots.
• Slugs and snails: protect tender spring shoots with barriers, hand-picking or a locally approved slug treatment.
• Powdery mildew: improve airflow, prevent the root zone from drying out and remove badly affected foliage.
• Poor flowering: deep shade, drought or excessive nitrogen can reduce bloom. Improve light exposure, water consistently and avoid high-nitrogen feeding.

Toxic to cats, dogs, horses and people if eaten. All parts contain irritant compounds, especially in fresh leaves and stems; ingestion can cause drooling, mouth irritation, vomiting or diarrhoea. Sap may irritate skin. Small accidental exposures are usually not severe, but seek medical or veterinary advice after ingestion or significant symptoms.

• Italian clematis (Clematis viticella)

  The species has much smaller, often nodding purple flowers. Its garden cultivars vary, so check the plant label when identifying large-flowered forms.

• Mountain clematis (Clematis montana)

  Usually a much larger, more vigorous climber with masses of smaller white or pink flowers in spring, rather than large purple flowers in summer.

Clematis comes from the Greek word for a climbing or twig-like plant, while jackmanii honours George Jackman, the English nurseryman associated with raising this hybrid.

Propagation. Take softwood or semi-ripe cuttings from late spring through summer, or layer a low stem into a pot or the ground. Seedlings will not reliably reproduce this hybrid's characteristics.

Accepted botanical name

Clematis jackmanii

Sources: GBIF (CC BY 4.0) and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.