Clematis

Pick a clematis matched to your scale and season

Vigorous spring climbers (Group 1): C. montana (3–10 m, May, white/pink), C. alpina (2–3 m, April, nodding bells), C. armandii (4–6 m evergreen, April, scented white). Large-flowered summer hybrids (Group 2): Nelly Moser (pink-striped), Henryi (white), Niobe (deep red), The President (purple) — 2–3 m, large saucer flowers May–July. Viticellas and late large-flowered (Group 3): Etoile Violette, Polish Spirit, Madame Julia Correvon, Princess Diana — 2–4 m, smaller flowers but longer season (June–September). The most reliable group for UK gardens. Texensis types (Group 3): tulip-shaped flowers, the only red-flowered group. For a first clematis: pick a Group 3 viticella — easy pruning, disease-resistant, prolific.

Plant 7–10 cm below the soil — DEEPER than the pot

The single most important clematis rule. Standard advice for most plants is plant at the same depth as the pot. For clematis, plant 7–10 cm deeper — the crown should sit below soil level. Why: clematis wilt is a fungal disease that attacks stems above the crown; deep planting means new shoots can emerge from below soil if the upper stems are infected, saving the plant. Without deep planting, a clematis-wilt attack often kills the entire plant.

Plant in sun with roots in shade

The classic clematis paradox: top growth wants 4–6 hours sun for flowering, but roots want cool moist conditions. Three ways to shade the roots: (1) a paving slab or large stone at the base; (2) low planting partners (hardy geraniums, lady's mantle) growing over the root zone; (3) a thick organic mulch around the base. Without root shading, clematis sulks, flowers poorly, and dries out in summer.

Know your pruning group

The most important clematis knowledge. Pruning the wrong group at the wrong time removes all the flowers. Group 1 (flowers on previous year's wood — montana, alpina, armandii): minimal pruning — just remove dead/damaged branches AFTER flowering (June). Group 2 (flowers on both old and new wood — large-flowered hybrids like Nelly Moser): light tidy in February, then a second light prune after first flowering for repeat blooms. Group 3 (flowers on current year's wood — viticellas, late large-flowered): cut all stems down to 30 cm above ground in February. If unsure, check the cultivar name and look up its group; getting this right is the difference between a flowering plant and disappointment.

Give a sturdy support

Clematis climb by twining leaf petioles around thin supports. Strong wire trellis, vine eyes and wires, or a sturdy obelisk are essential. Fences need wire or trellis added — clematis can't grip flat wood. Don't expect clematis to climb a bare post or tree trunk — they need the thin support to grip. The support also needs to bear weight; mature montana types can weigh 30+ kg.

Feed and water generously

Clematis are hungry and thirsty. In spring: a thick mulch of garden compost or well-rotted manure around the base, plus a handful of slow-release general-purpose fertiliser. Through summer: deep weekly watering in dry spells — clematis flop and drop flowers when stressed. Pot-grown clematis need much more frequent watering. Feed with liquid tomato food every 2 weeks during flowering for the best blooms.

Manage clematis wilt

Clematis wilt (Calophoma clematidina) is the main UK clematis disease. Symptoms: stems suddenly wilt and turn black, often after first flowering, sometimes the whole plant collapses overnight. Three responses. (1) Cut affected stems to below the wilt point (often to ground level); the plant usually re-shoots from the deep-planted crown. (2) Keep watering — the roots are usually fine. (3) For severe repeated wilt, the resistant Group 3 viticella types and species clematis are far less affected — replace the susceptible large-flowered Group 2 hybrid with a viticella.

Cut to the ground every 3–5 years (renovation)

For an overgrown, tangled, bare-at-base mess: clematis tolerate radical renovation. In February, cut every stem down to 30 cm above the ground. The plant resprouts vigorously from the crown — full flowering normally returns the following year. This works for all three groups, though Group 1 will skip a flowering season; Groups 2 and 3 usually flower the same year on new growth.