About
Horizon Monarch' is a shrub up to 2m high, with evergreen, leathery, dark green leaves, up to 18cm long, and very large upright trusses of fifteen or more dark pink buds which open to funnel-shaped flowers, 10cm across, which are pale, warm yellow inside with small pink flares, and pale pink on the outside, from late spring to early summer.
About the genus
Rhododendron can be evergreen or deciduous shrubs or trees, with simple leaves, sometimes with a dense colourful indumentum of hairs on the lower side, and funnel-shaped, bell-shaped or tubular flowers that may be solitary or in short racemes
Growing conditions
SunlightPartial shade
Soil typeClay, Loam, Sand
Soil pHAcid
Soil moistureMoist but well-drained
AspectNorth-facing, West-facing, South-facing, East-facing
ExposureSheltered
UK hardinessH4
Plant details
Plant typeShrubs
HabitBushy
FoliageEvergreen
Height1.5-2.5 metres
Spread1.5-2.5 metres
Time to full height5-10 years
Suggested usesCottage and informal garden, City and courtyard gardens
ToxicityHarmful if eaten. Wear gloves and other protective equipment when handling. Pets (dogs, cats, rabbits, tortoises) Harmful if eaten - for further information and contact numbers regarding pets, see the HTA guide to potentially harmful plants
Care notes
CultivationGrow in light dappled shade, in a site sheltered from cold, dry winds and late frosts, in moist but well-drained, humus-rich, acidic soil, preferably between pH4.5 and pH5.5; for more advice, see rhododendron cultivation
PruningPruning group 1 (little or no pruning of trees and shrubs) or pruning group 8 (early-flowering evergreen shrubs)
PropagationPropagate by heeled semi-ripe cuttings in late summer, by layering in autumn, or by grafting in late winter or late summer
Pest resistanceMay be susceptible to vine weevil, rhododendron and azalea whitefly, rhododendron leafhopper, pieris lacebug, scale insects, caterpillars and aphids
Disease resistanceMay be susceptible to various Rhododendron diseases including powdery mildews, rhododendron petal blight, rhododendron bud blast, silver leaf and honey fungus