Flowers

Holes bored into the side of the flower buds

Budworm

Flowers

Flowers not the right colour

Weather

Flowers

Flowers don't stay on the plant for long.

Over fertilizing

Flowers

Flowers go brown at the edges.

Thrips

Flowers

Flowers are single, not double during spring on varieties that should flower double in the spring.

Single flowers

Flowers

Small flowers

Water stress.

Flowers

Flowers come out green in early spring

Weather

Leaves

Leaves eaten starting from the outside.

Caterpillars

Leaves

Holes in the leaves, usually in the middle of the leaves

Slugs and Snails

Leaves

Leaves going brown starting from the base and progressing up the plant.

Water stress

Leaves and Stems

White powder on the leaves and stems followed by black blotches

Powdery Mildew.

Stems

New shoots fail to appear in spring. On closer inspection they are chewed off.

Slugs and Snails

Stems

Bark stripped off the plant creating a pattern of brown bark and no bark

Slugs and Snails

Whole Plant

Partial or complete collapse of the plant

Clematis Wilt

Whole Plant

Whole plant turns black starting from the new growth.

Over watering