Large-flowered clematis

Large-flowered clematis: how do you recognise it?

Habit

Climber 2–3 m tall and 1–1.5 m wide. It climbs by twisting its leaf stalks around wire, mesh or thin twigs.

Leaves

Usually made up of three to five oval leaflets, in opposite pairs on thin, brittle stems.

Flowers

Flat flowers 10–20 cm across, with six to eight broad ‘petals’ around a centre of stamens. There are double-flowered varieties too.

Seed heads

After flowering, silvery, feathery seed heads that stay decorative for weeks.

Roots

Fine and fleshy. They like to be cool and moist, in shade.

Flowering: May–September · Plants: March–May and September–October · Pruning: February

Why grow it?

• Huge flowers in almost every colour, from May to September depending on the variety.
• Takes up little ground space: ideal for a small garden, a patio or a pot.
• Climbs through a climbing rose, a shrub or an old tree and adds a second wave of flowers.
• After flowering come elegant, silvery seed heads.
• Fully hardy and, well planted, a plant for many years.

Large-flowered clematis: where does it grow best?

• Sun or partial shade, with the flowers in the light and the base in shade. Pale varieties such as ‘Nelly Moser’ fade in strong sun and do better facing east or north.
• Humus-rich, well-drained soil that does not dry out: sand, loam or clay, neutral to chalky.
• Sheltered from strong wind: the stems are brittle.
• Always give a support of thin wires or mesh; it cannot grip thick posts.
• Allow 1–1.5 m width per plant.

Light

Sun and partial shade

Soil type

Sand, loam or clay

Acidity

Neutral or chalky

Moisture

Normal

Size

3 m tall, 1.5 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Climbing rose: A classic: the clematis climbs through the rose and extends the flowering.
• Hardy geranium: Shades the base and flowers at the same time.
• Lady’s mantle: Low, fresh green leaves that keep the roots cool.
• Hosta: Large leaves for a cool, shady base.

Large-flowered clematis: when and how to plant it?

Plant in March–May and September–October.

1. Plant in March–May or September–October. Soak the pot in a bucket of water for a quarter of an hour first.
2. Dig a hole 40 × 40 cm, at least 30 cm from the wall or fence, and mix in a generous spadeful of compost.
3. Set the plant 5–10 cm deeper than it was in the pot: after clematis wilt it can then regrow from dormant buds below ground.
4. Lean the plant towards the support along a cane and tie the stems in gently.
5. Firm in and water generously, at least a full watering can.
6. Shade the base with mulch, a few flat stones or low perennials.

Care

Watering

In the first year, a full watering can every week in dry weather. Later too, water generously at the base in dry summers.

Feeding

Compost or organic fertiliser in March. During flowering, a high-potash feed for flowering plants helps.

Cool roots

A mulch or low plants at the base keep the roots cool and moist.

Tying in

In spring, tie in young shoots every week and spread them out: they snap easily and tangle otherwise.

Deadheading

Remove faded flowers; with varieties that flower in May–June this often gives a second flush in late summer.

In a pot

Choose a pot at least 40 cm deep and wide, with good potting compost and a drainage layer. Water daily in summer.

Tip: Head in the sun, feet in the shade: lay a few flat stones over the roots or plant low perennials in front, and your clematis will flower more richly for years.

Large-flowered clematis: when to prune it?

Pruning months: February.

When: In February, before the buds break. How hard you prune depends on when your variety flowers.

How:

• Varieties that flower in May–June: remove dead stems and lightly shorten the rest to just above a pair of strong buds.
• Varieties that only flower from July, such as ‘Jackmanii’: cut all stems back to 20–30 cm above the ground, just above a pair of strong buds.
• In the first spring after planting, cut all stems back to about 30 cm; the plant then branches from the base.
• Not sure which variety you have? Watch when it flowers: before mid-June, prune lightly; from July, prune hard.

Caution: If you prune an early-flowering variety hard in February, you lose the first flush: it forms on last year’s wood.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Cuttings

In May–June: pieces of young stem with one leaf joint, cut just above the joint and 3–4 cm below it. Insert them in moist cutting compost under plastic; they root in 4–6 weeks.

Layering

In spring: bend a stem down to the ground, lightly nick the bark at a leaf joint, cover with soil and weigh it down with a stone. Sever it after a year.

Large-flowered clematis: how does it get through the winter?

Hardy to −25 °C.

• Fully hardy in Belgium, to about −25 °C. An established plant needs no protection.
• A layer of mulch around the base helps young plants through their first winter.
• In a pot: raise the pot on feet against a wall and wrap it in hessian or bubble wrap.
• In winter the stems look dead, but they carry buds: wait until February to prune.

Diseases and pests

• Clematis wilt: Shoots suddenly collapse and the leaves turn black. Cut back to healthy growth, below ground level if necessary. Thanks to deep planting it usually regrows.
• Slugs and snails: Eat young shoots in spring. Pick them off in the evening and protect the base.
• Powdery mildew: White powder on the leaves in late summer, especially in dry weather. Water enough and keep growth airy.
• Aphids: On young shoots. Hose them off; ladybirds help.
• Bare base: The lower stems are often bare. Plant low perennials or a small shrub in front.

Through the year

• February: Prune according to variety: shorten lightly or cut back to 20–30 cm.
• March: Planting. Compost around the base. Tie in new shoots.
• April: Planting. Tie in shoots weekly. Watch for slugs.
• May: First flowers on early varieties. Planting is still possible. Take cuttings.
• June: Deadhead for a second flush. Water in dry weather.
• July: Late varieties in flower. Give a high-potash feed. Water.
• August: In flower. Water in dry weather. Watch for mildew.
• September: Last flowers and silvery seed heads. Planting.
• October: Planting.
• November: Mulch around the base of young plants.

Edible and useful

Not edible. All parts of clematis are poisonous: when the plant is damaged it releases protoanemonin, an acrid substance also found in buttercups and anemones. On the skin the sap can cause redness, itching and blisters, especially in people who often prune with bare hands; in the mouth it causes a burning feeling, drooling, vomiting and stomach ache. The acrid, bitter taste puts off most people and animals, but keep small children, dogs, cats, rabbits and guinea pigs away from the plant and the clippings. Horses and other livestock can eat more of it if they reach a clematis over the fence or find the clippings: do not plant it along a field, and never throw the clippings into a field, pen or hutch. Wear gloves when pruning and tying in, and wash your hands afterwards. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• What we call petals are actually coloured sepals in clematis. The flower has no true petals.
• ‘Jackmanii’ was raised in 1858 by the English Jackman nursery and is still one of the most popular clematis.
• Clematis has no tendrils: it climbs with its leaf stalks, which twist around wire or thin twigs.