Rhododendron 'Calsap'

Rhododendron 'Calsap' is recognised at a glance. The almost white, faintly lilac flower carries a broad dark cherry blotch on its upper lobe, as though laid on with a brush. A conical truss holds up to eighteen of them.

Grow it as a specimen on a lawn, in a group under light-canopied trees, or beside a path where the markings can be seen close up. In twelve years it makes 1.2 m tall by 1.8 m wide - wider than high, so allow generous space. The foliage is evergreen, so the bush stays decorative through winter too.

Key characteristics:

• What makes it special: Every part of the plant is toxic if eaten - to people and to dogs, cats and rabbits alike, so it is best to prune the shrub wearing gloves.
• Dimensions: At 12 years it spreads to 1.2 m tall and 1.8 m wide.
• Hardiness: Hardy down to -34 °C (USDA zone 4).
• Flowering: In late May to June it opens white flowers with a dark red blotch, up to 18 to an inflorescence.
• Light: Full sun or light partial shade; the spot must be sheltered from strong wind and frost cracks.
• Soil: It needs acidic, humus-rich, evenly moist yet well-drained soil - standing water is the one thing it dislikes.
• Watering: Water evenly at a medium rate: the surface roots must not dry out.
• Care: Pruning is minimal, RHS group 8; mulch every year, ideally with leaf mould.
• Landscape use: Striking as a specimen, in a group in an informal garden, in a flower border and against a wall.
• Origin: A 'Catalgla' x 'Sappho' hybrid raised by M.W. Michener in the USA: crossed in 1965, registered in 1986.